1 The Definitive KVM (Kernel-based Virtual Machine) API Documentation
2 ===================================================================
7 The kvm API is a set of ioctls that are issued to control various aspects
8 of a virtual machine. The ioctls belong to three classes
10 - System ioctls: These query and set global attributes which affect the
11 whole kvm subsystem. In addition a system ioctl is used to create
14 - VM ioctls: These query and set attributes that affect an entire virtual
15 machine, for example memory layout. In addition a VM ioctl is used to
16 create virtual cpus (vcpus) and devices.
18 Only run VM ioctls from the same process (address space) that was used
21 - vcpu ioctls: These query and set attributes that control the operation
22 of a single virtual cpu.
24 Only run vcpu ioctls from the same thread that was used to create the
27 - device ioctls: These query and set attributes that control the operation
30 device ioctls must be issued from the same process (address space) that
31 was used to create the VM.
36 The kvm API is centered around file descriptors. An initial
37 open("/dev/kvm") obtains a handle to the kvm subsystem; this handle
38 can be used to issue system ioctls. A KVM_CREATE_VM ioctl on this
39 handle will create a VM file descriptor which can be used to issue VM
40 ioctls. A KVM_CREATE_VCPU or KVM_CREATE_DEVICE ioctl on a VM fd will
41 create a virtual cpu or device and return a file descriptor pointing to
42 the new resource. Finally, ioctls on a vcpu or device fd can be used
43 to control the vcpu or device. For vcpus, this includes the important
44 task of actually running guest code.
46 In general file descriptors can be migrated among processes by means
47 of fork() and the SCM_RIGHTS facility of unix domain socket. These
48 kinds of tricks are explicitly not supported by kvm. While they will
49 not cause harm to the host, their actual behavior is not guaranteed by
50 the API. The only supported use is one virtual machine per process,
51 and one vcpu per thread.
57 As of Linux 2.6.22, the KVM ABI has been stabilized: no backward
58 incompatible change are allowed. However, there is an extension
59 facility that allows backward-compatible extensions to the API to be
62 The extension mechanism is not based on the Linux version number.
63 Instead, kvm defines extension identifiers and a facility to query
64 whether a particular extension identifier is available. If it is, a
65 set of ioctls is available for application use.
71 This section describes ioctls that can be used to control kvm guests.
72 For each ioctl, the following information is provided along with a
75 Capability: which KVM extension provides this ioctl. Can be 'basic',
76 which means that is will be provided by any kernel that supports
77 API version 12 (see section 4.1), a KVM_CAP_xyz constant, which
78 means availability needs to be checked with KVM_CHECK_EXTENSION
79 (see section 4.4), or 'none' which means that while not all kernels
80 support this ioctl, there's no capability bit to check its
81 availability: for kernels that don't support the ioctl,
82 the ioctl returns -ENOTTY.
84 Architectures: which instruction set architectures provide this ioctl.
85 x86 includes both i386 and x86_64.
87 Type: system, vm, or vcpu.
89 Parameters: what parameters are accepted by the ioctl.
91 Returns: the return value. General error numbers (EBADF, ENOMEM, EINVAL)
92 are not detailed, but errors with specific meanings are.
95 4.1 KVM_GET_API_VERSION
101 Returns: the constant KVM_API_VERSION (=12)
103 This identifies the API version as the stable kvm API. It is not
104 expected that this number will change. However, Linux 2.6.20 and
105 2.6.21 report earlier versions; these are not documented and not
106 supported. Applications should refuse to run if KVM_GET_API_VERSION
107 returns a value other than 12. If this check passes, all ioctls
108 described as 'basic' will be available.
116 Parameters: machine type identifier (KVM_VM_*)
117 Returns: a VM fd that can be used to control the new virtual machine.
119 The new VM has no virtual cpus and no memory. An mmap() of a VM fd
120 will access the virtual machine's physical address space; offset zero
121 corresponds to guest physical address zero. Use of mmap() on a VM fd
122 is discouraged if userspace memory allocation (KVM_CAP_USER_MEMORY) is
124 You most certainly want to use 0 as machine type.
126 In order to create user controlled virtual machines on S390, check
127 KVM_CAP_S390_UCONTROL and use the flag KVM_VM_S390_UCONTROL as
128 privileged user (CAP_SYS_ADMIN).
131 4.3 KVM_GET_MSR_INDEX_LIST
136 Parameters: struct kvm_msr_list (in/out)
137 Returns: 0 on success; -1 on error
139 E2BIG: the msr index list is to be to fit in the array specified by
142 struct kvm_msr_list {
143 __u32 nmsrs; /* number of msrs in entries */
147 This ioctl returns the guest msrs that are supported. The list varies
148 by kvm version and host processor, but does not change otherwise. The
149 user fills in the size of the indices array in nmsrs, and in return
150 kvm adjusts nmsrs to reflect the actual number of msrs and fills in
151 the indices array with their numbers.
153 Note: if kvm indicates supports MCE (KVM_CAP_MCE), then the MCE bank MSRs are
154 not returned in the MSR list, as different vcpus can have a different number
155 of banks, as set via the KVM_X86_SETUP_MCE ioctl.
158 4.4 KVM_CHECK_EXTENSION
160 Capability: basic, KVM_CAP_CHECK_EXTENSION_VM for vm ioctl
162 Type: system ioctl, vm ioctl
163 Parameters: extension identifier (KVM_CAP_*)
164 Returns: 0 if unsupported; 1 (or some other positive integer) if supported
166 The API allows the application to query about extensions to the core
167 kvm API. Userspace passes an extension identifier (an integer) and
168 receives an integer that describes the extension availability.
169 Generally 0 means no and 1 means yes, but some extensions may report
170 additional information in the integer return value.
172 Based on their initialization different VMs may have different capabilities.
173 It is thus encouraged to use the vm ioctl to query for capabilities (available
174 with KVM_CAP_CHECK_EXTENSION_VM on the vm fd)
176 4.5 KVM_GET_VCPU_MMAP_SIZE
182 Returns: size of vcpu mmap area, in bytes
184 The KVM_RUN ioctl (cf.) communicates with userspace via a shared
185 memory region. This ioctl returns the size of that region. See the
186 KVM_RUN documentation for details.
189 4.6 KVM_SET_MEMORY_REGION
194 Parameters: struct kvm_memory_region (in)
195 Returns: 0 on success, -1 on error
197 This ioctl is obsolete and has been removed.
205 Parameters: vcpu id (apic id on x86)
206 Returns: vcpu fd on success, -1 on error
208 This API adds a vcpu to a virtual machine. The vcpu id is a small integer
209 in the range [0, max_vcpus).
211 The recommended max_vcpus value can be retrieved using the KVM_CAP_NR_VCPUS of
212 the KVM_CHECK_EXTENSION ioctl() at run-time.
213 The maximum possible value for max_vcpus can be retrieved using the
214 KVM_CAP_MAX_VCPUS of the KVM_CHECK_EXTENSION ioctl() at run-time.
216 If the KVM_CAP_NR_VCPUS does not exist, you should assume that max_vcpus is 4
218 If the KVM_CAP_MAX_VCPUS does not exist, you should assume that max_vcpus is
219 same as the value returned from KVM_CAP_NR_VCPUS.
221 On powerpc using book3s_hv mode, the vcpus are mapped onto virtual
222 threads in one or more virtual CPU cores. (This is because the
223 hardware requires all the hardware threads in a CPU core to be in the
224 same partition.) The KVM_CAP_PPC_SMT capability indicates the number
225 of vcpus per virtual core (vcore). The vcore id is obtained by
226 dividing the vcpu id by the number of vcpus per vcore. The vcpus in a
227 given vcore will always be in the same physical core as each other
228 (though that might be a different physical core from time to time).
229 Userspace can control the threading (SMT) mode of the guest by its
230 allocation of vcpu ids. For example, if userspace wants
231 single-threaded guest vcpus, it should make all vcpu ids be a multiple
232 of the number of vcpus per vcore.
234 For virtual cpus that have been created with S390 user controlled virtual
235 machines, the resulting vcpu fd can be memory mapped at page offset
236 KVM_S390_SIE_PAGE_OFFSET in order to obtain a memory map of the virtual
237 cpu's hardware control block.
240 4.8 KVM_GET_DIRTY_LOG (vm ioctl)
245 Parameters: struct kvm_dirty_log (in/out)
246 Returns: 0 on success, -1 on error
248 /* for KVM_GET_DIRTY_LOG */
249 struct kvm_dirty_log {
253 void __user *dirty_bitmap; /* one bit per page */
258 Given a memory slot, return a bitmap containing any pages dirtied
259 since the last call to this ioctl. Bit 0 is the first page in the
260 memory slot. Ensure the entire structure is cleared to avoid padding
263 If KVM_CAP_MULTI_ADDRESS_SPACE is available, bits 16-31 specifies
264 the address space for which you want to return the dirty bitmap.
265 They must be less than the value that KVM_CHECK_EXTENSION returns for
266 the KVM_CAP_MULTI_ADDRESS_SPACE capability.
269 4.9 KVM_SET_MEMORY_ALIAS
274 Parameters: struct kvm_memory_alias (in)
275 Returns: 0 (success), -1 (error)
277 This ioctl is obsolete and has been removed.
286 Returns: 0 on success, -1 on error
288 EINTR: an unmasked signal is pending
290 This ioctl is used to run a guest virtual cpu. While there are no
291 explicit parameters, there is an implicit parameter block that can be
292 obtained by mmap()ing the vcpu fd at offset 0, with the size given by
293 KVM_GET_VCPU_MMAP_SIZE. The parameter block is formatted as a 'struct
294 kvm_run' (see below).
300 Architectures: all except ARM, arm64
302 Parameters: struct kvm_regs (out)
303 Returns: 0 on success, -1 on error
305 Reads the general purpose registers from the vcpu.
309 /* out (KVM_GET_REGS) / in (KVM_SET_REGS) */
310 __u64 rax, rbx, rcx, rdx;
311 __u64 rsi, rdi, rsp, rbp;
312 __u64 r8, r9, r10, r11;
313 __u64 r12, r13, r14, r15;
319 /* out (KVM_GET_REGS) / in (KVM_SET_REGS) */
330 Architectures: all except ARM, arm64
332 Parameters: struct kvm_regs (in)
333 Returns: 0 on success, -1 on error
335 Writes the general purpose registers into the vcpu.
337 See KVM_GET_REGS for the data structure.
343 Architectures: x86, ppc
345 Parameters: struct kvm_sregs (out)
346 Returns: 0 on success, -1 on error
348 Reads special registers from the vcpu.
352 struct kvm_segment cs, ds, es, fs, gs, ss;
353 struct kvm_segment tr, ldt;
354 struct kvm_dtable gdt, idt;
355 __u64 cr0, cr2, cr3, cr4, cr8;
358 __u64 interrupt_bitmap[(KVM_NR_INTERRUPTS + 63) / 64];
361 /* ppc -- see arch/powerpc/include/uapi/asm/kvm.h */
363 interrupt_bitmap is a bitmap of pending external interrupts. At most
364 one bit may be set. This interrupt has been acknowledged by the APIC
365 but not yet injected into the cpu core.
371 Architectures: x86, ppc
373 Parameters: struct kvm_sregs (in)
374 Returns: 0 on success, -1 on error
376 Writes special registers into the vcpu. See KVM_GET_SREGS for the
385 Parameters: struct kvm_translation (in/out)
386 Returns: 0 on success, -1 on error
388 Translates a virtual address according to the vcpu's current address
391 struct kvm_translation {
393 __u64 linear_address;
396 __u64 physical_address;
407 Architectures: x86, ppc, mips
409 Parameters: struct kvm_interrupt (in)
410 Returns: 0 on success, negative on failure.
412 Queues a hardware interrupt vector to be injected.
414 /* for KVM_INTERRUPT */
415 struct kvm_interrupt {
422 Returns: 0 on success,
423 -EEXIST if an interrupt is already enqueued
424 -EINVAL the the irq number is invalid
425 -ENXIO if the PIC is in the kernel
426 -EFAULT if the pointer is invalid
428 Note 'irq' is an interrupt vector, not an interrupt pin or line. This
429 ioctl is useful if the in-kernel PIC is not used.
433 Queues an external interrupt to be injected. This ioctl is overleaded
434 with 3 different irq values:
438 This injects an edge type external interrupt into the guest once it's ready
439 to receive interrupts. When injected, the interrupt is done.
441 b) KVM_INTERRUPT_UNSET
443 This unsets any pending interrupt.
445 Only available with KVM_CAP_PPC_UNSET_IRQ.
447 c) KVM_INTERRUPT_SET_LEVEL
449 This injects a level type external interrupt into the guest context. The
450 interrupt stays pending until a specific ioctl with KVM_INTERRUPT_UNSET
453 Only available with KVM_CAP_PPC_IRQ_LEVEL.
455 Note that any value for 'irq' other than the ones stated above is invalid
456 and incurs unexpected behavior.
460 Queues an external interrupt to be injected into the virtual CPU. A negative
461 interrupt number dequeues the interrupt.
472 Support for this has been removed. Use KVM_SET_GUEST_DEBUG instead.
480 Parameters: struct kvm_msrs (in/out)
481 Returns: 0 on success, -1 on error
483 Reads model-specific registers from the vcpu. Supported msr indices can
484 be obtained using KVM_GET_MSR_INDEX_LIST.
487 __u32 nmsrs; /* number of msrs in entries */
490 struct kvm_msr_entry entries[0];
493 struct kvm_msr_entry {
499 Application code should set the 'nmsrs' member (which indicates the
500 size of the entries array) and the 'index' member of each array entry.
501 kvm will fill in the 'data' member.
509 Parameters: struct kvm_msrs (in)
510 Returns: 0 on success, -1 on error
512 Writes model-specific registers to the vcpu. See KVM_GET_MSRS for the
515 Application code should set the 'nmsrs' member (which indicates the
516 size of the entries array), and the 'index' and 'data' members of each
525 Parameters: struct kvm_cpuid (in)
526 Returns: 0 on success, -1 on error
528 Defines the vcpu responses to the cpuid instruction. Applications
529 should use the KVM_SET_CPUID2 ioctl if available.
532 struct kvm_cpuid_entry {
541 /* for KVM_SET_CPUID */
545 struct kvm_cpuid_entry entries[0];
549 4.21 KVM_SET_SIGNAL_MASK
554 Parameters: struct kvm_signal_mask (in)
555 Returns: 0 on success, -1 on error
557 Defines which signals are blocked during execution of KVM_RUN. This
558 signal mask temporarily overrides the threads signal mask. Any
559 unblocked signal received (except SIGKILL and SIGSTOP, which retain
560 their traditional behaviour) will cause KVM_RUN to return with -EINTR.
562 Note the signal will only be delivered if not blocked by the original
565 /* for KVM_SET_SIGNAL_MASK */
566 struct kvm_signal_mask {
577 Parameters: struct kvm_fpu (out)
578 Returns: 0 on success, -1 on error
580 Reads the floating point state from the vcpu.
582 /* for KVM_GET_FPU and KVM_SET_FPU */
587 __u8 ftwx; /* in fxsave format */
603 Parameters: struct kvm_fpu (in)
604 Returns: 0 on success, -1 on error
606 Writes the floating point state to the vcpu.
608 /* for KVM_GET_FPU and KVM_SET_FPU */
613 __u8 ftwx; /* in fxsave format */
624 4.24 KVM_CREATE_IRQCHIP
626 Capability: KVM_CAP_IRQCHIP, KVM_CAP_S390_IRQCHIP (s390)
627 Architectures: x86, ARM, arm64, s390
630 Returns: 0 on success, -1 on error
632 Creates an interrupt controller model in the kernel.
633 On x86, creates a virtual ioapic, a virtual PIC (two PICs, nested), and sets up
634 future vcpus to have a local APIC. IRQ routing for GSIs 0-15 is set to both
635 PIC and IOAPIC; GSI 16-23 only go to the IOAPIC.
636 On ARM/arm64, a GICv2 is created. Any other GIC versions require the usage of
637 KVM_CREATE_DEVICE, which also supports creating a GICv2. Using
638 KVM_CREATE_DEVICE is preferred over KVM_CREATE_IRQCHIP for GICv2.
639 On s390, a dummy irq routing table is created.
641 Note that on s390 the KVM_CAP_S390_IRQCHIP vm capability needs to be enabled
642 before KVM_CREATE_IRQCHIP can be used.
647 Capability: KVM_CAP_IRQCHIP
648 Architectures: x86, arm, arm64
650 Parameters: struct kvm_irq_level
651 Returns: 0 on success, -1 on error
653 Sets the level of a GSI input to the interrupt controller model in the kernel.
654 On some architectures it is required that an interrupt controller model has
655 been previously created with KVM_CREATE_IRQCHIP. Note that edge-triggered
656 interrupts require the level to be set to 1 and then back to 0.
658 On real hardware, interrupt pins can be active-low or active-high. This
659 does not matter for the level field of struct kvm_irq_level: 1 always
660 means active (asserted), 0 means inactive (deasserted).
662 x86 allows the operating system to program the interrupt polarity
663 (active-low/active-high) for level-triggered interrupts, and KVM used
664 to consider the polarity. However, due to bitrot in the handling of
665 active-low interrupts, the above convention is now valid on x86 too.
666 This is signaled by KVM_CAP_X86_IOAPIC_POLARITY_IGNORED. Userspace
667 should not present interrupts to the guest as active-low unless this
668 capability is present (or unless it is not using the in-kernel irqchip,
672 ARM/arm64 can signal an interrupt either at the CPU level, or at the
673 in-kernel irqchip (GIC), and for in-kernel irqchip can tell the GIC to
674 use PPIs designated for specific cpus. The irq field is interpreted
677 Â bits: | 31 ... 24 | 23 ... 16 | 15 ... 0 |
678 field: | irq_type | vcpu_index | irq_id |
680 The irq_type field has the following values:
681 - irq_type[0]: out-of-kernel GIC: irq_id 0 is IRQ, irq_id 1 is FIQ
682 - irq_type[1]: in-kernel GIC: SPI, irq_id between 32 and 1019 (incl.)
683 (the vcpu_index field is ignored)
684 - irq_type[2]: in-kernel GIC: PPI, irq_id between 16 and 31 (incl.)
686 (The irq_id field thus corresponds nicely to the IRQ ID in the ARM GIC specs)
688 In both cases, level is used to assert/deassert the line.
690 struct kvm_irq_level {
693 __s32 status; /* not used for KVM_IRQ_LEVEL */
695 __u32 level; /* 0 or 1 */
701 Capability: KVM_CAP_IRQCHIP
704 Parameters: struct kvm_irqchip (in/out)
705 Returns: 0 on success, -1 on error
707 Reads the state of a kernel interrupt controller created with
708 KVM_CREATE_IRQCHIP into a buffer provided by the caller.
711 __u32 chip_id; /* 0 = PIC1, 1 = PIC2, 2 = IOAPIC */
714 char dummy[512]; /* reserving space */
715 struct kvm_pic_state pic;
716 struct kvm_ioapic_state ioapic;
723 Capability: KVM_CAP_IRQCHIP
726 Parameters: struct kvm_irqchip (in)
727 Returns: 0 on success, -1 on error
729 Sets the state of a kernel interrupt controller created with
730 KVM_CREATE_IRQCHIP from a buffer provided by the caller.
733 __u32 chip_id; /* 0 = PIC1, 1 = PIC2, 2 = IOAPIC */
736 char dummy[512]; /* reserving space */
737 struct kvm_pic_state pic;
738 struct kvm_ioapic_state ioapic;
743 4.28 KVM_XEN_HVM_CONFIG
745 Capability: KVM_CAP_XEN_HVM
748 Parameters: struct kvm_xen_hvm_config (in)
749 Returns: 0 on success, -1 on error
751 Sets the MSR that the Xen HVM guest uses to initialize its hypercall
752 page, and provides the starting address and size of the hypercall
753 blobs in userspace. When the guest writes the MSR, kvm copies one
754 page of a blob (32- or 64-bit, depending on the vcpu mode) to guest
757 struct kvm_xen_hvm_config {
770 Capability: KVM_CAP_ADJUST_CLOCK
773 Parameters: struct kvm_clock_data (out)
774 Returns: 0 on success, -1 on error
776 Gets the current timestamp of kvmclock as seen by the current guest. In
777 conjunction with KVM_SET_CLOCK, it is used to ensure monotonicity on scenarios
780 struct kvm_clock_data {
781 __u64 clock; /* kvmclock current value */
789 Capability: KVM_CAP_ADJUST_CLOCK
792 Parameters: struct kvm_clock_data (in)
793 Returns: 0 on success, -1 on error
795 Sets the current timestamp of kvmclock to the value specified in its parameter.
796 In conjunction with KVM_GET_CLOCK, it is used to ensure monotonicity on scenarios
799 struct kvm_clock_data {
800 __u64 clock; /* kvmclock current value */
806 4.31 KVM_GET_VCPU_EVENTS
808 Capability: KVM_CAP_VCPU_EVENTS
809 Extended by: KVM_CAP_INTR_SHADOW
812 Parameters: struct kvm_vcpu_event (out)
813 Returns: 0 on success, -1 on error
815 Gets currently pending exceptions, interrupts, and NMIs as well as related
818 struct kvm_vcpu_events {
848 Only two fields are defined in the flags field:
850 - KVM_VCPUEVENT_VALID_SHADOW may be set in the flags field to signal that
851 interrupt.shadow contains a valid state.
853 - KVM_VCPUEVENT_VALID_SMM may be set in the flags field to signal that
854 smi contains a valid state.
856 4.32 KVM_SET_VCPU_EVENTS
858 Capability: KVM_CAP_VCPU_EVENTS
859 Extended by: KVM_CAP_INTR_SHADOW
862 Parameters: struct kvm_vcpu_event (in)
863 Returns: 0 on success, -1 on error
865 Set pending exceptions, interrupts, and NMIs as well as related states of the
868 See KVM_GET_VCPU_EVENTS for the data structure.
870 Fields that may be modified asynchronously by running VCPUs can be excluded
871 from the update. These fields are nmi.pending, sipi_vector, smi.smm,
872 smi.pending. Keep the corresponding bits in the flags field cleared to
873 suppress overwriting the current in-kernel state. The bits are:
875 KVM_VCPUEVENT_VALID_NMI_PENDING - transfer nmi.pending to the kernel
876 KVM_VCPUEVENT_VALID_SIPI_VECTOR - transfer sipi_vector
877 KVM_VCPUEVENT_VALID_SMM - transfer the smi sub-struct.
879 If KVM_CAP_INTR_SHADOW is available, KVM_VCPUEVENT_VALID_SHADOW can be set in
880 the flags field to signal that interrupt.shadow contains a valid state and
881 shall be written into the VCPU.
883 KVM_VCPUEVENT_VALID_SMM can only be set if KVM_CAP_X86_SMM is available.
886 4.33 KVM_GET_DEBUGREGS
888 Capability: KVM_CAP_DEBUGREGS
891 Parameters: struct kvm_debugregs (out)
892 Returns: 0 on success, -1 on error
894 Reads debug registers from the vcpu.
896 struct kvm_debugregs {
905 4.34 KVM_SET_DEBUGREGS
907 Capability: KVM_CAP_DEBUGREGS
910 Parameters: struct kvm_debugregs (in)
911 Returns: 0 on success, -1 on error
913 Writes debug registers into the vcpu.
915 See KVM_GET_DEBUGREGS for the data structure. The flags field is unused
916 yet and must be cleared on entry.
919 4.35 KVM_SET_USER_MEMORY_REGION
921 Capability: KVM_CAP_USER_MEM
924 Parameters: struct kvm_userspace_memory_region (in)
925 Returns: 0 on success, -1 on error
927 struct kvm_userspace_memory_region {
930 __u64 guest_phys_addr;
931 __u64 memory_size; /* bytes */
932 __u64 userspace_addr; /* start of the userspace allocated memory */
935 /* for kvm_memory_region::flags */
936 #define KVM_MEM_LOG_DIRTY_PAGES (1UL << 0)
937 #define KVM_MEM_READONLY (1UL << 1)
939 This ioctl allows the user to create or modify a guest physical memory
940 slot. When changing an existing slot, it may be moved in the guest
941 physical memory space, or its flags may be modified. It may not be
942 resized. Slots may not overlap in guest physical address space.
944 If KVM_CAP_MULTI_ADDRESS_SPACE is available, bits 16-31 of "slot"
945 specifies the address space which is being modified. They must be
946 less than the value that KVM_CHECK_EXTENSION returns for the
947 KVM_CAP_MULTI_ADDRESS_SPACE capability. Slots in separate address spaces
948 are unrelated; the restriction on overlapping slots only applies within
951 Memory for the region is taken starting at the address denoted by the
952 field userspace_addr, which must point at user addressable memory for
953 the entire memory slot size. Any object may back this memory, including
954 anonymous memory, ordinary files, and hugetlbfs.
956 It is recommended that the lower 21 bits of guest_phys_addr and userspace_addr
957 be identical. This allows large pages in the guest to be backed by large
960 The flags field supports two flags: KVM_MEM_LOG_DIRTY_PAGES and
961 KVM_MEM_READONLY. The former can be set to instruct KVM to keep track of
962 writes to memory within the slot. See KVM_GET_DIRTY_LOG ioctl to know how to
963 use it. The latter can be set, if KVM_CAP_READONLY_MEM capability allows it,
964 to make a new slot read-only. In this case, writes to this memory will be
965 posted to userspace as KVM_EXIT_MMIO exits.
967 When the KVM_CAP_SYNC_MMU capability is available, changes in the backing of
968 the memory region are automatically reflected into the guest. For example, an
969 mmap() that affects the region will be made visible immediately. Another
970 example is madvise(MADV_DROP).
972 It is recommended to use this API instead of the KVM_SET_MEMORY_REGION ioctl.
973 The KVM_SET_MEMORY_REGION does not allow fine grained control over memory
974 allocation and is deprecated.
977 4.36 KVM_SET_TSS_ADDR
979 Capability: KVM_CAP_SET_TSS_ADDR
982 Parameters: unsigned long tss_address (in)
983 Returns: 0 on success, -1 on error
985 This ioctl defines the physical address of a three-page region in the guest
986 physical address space. The region must be within the first 4GB of the
987 guest physical address space and must not conflict with any memory slot
988 or any mmio address. The guest may malfunction if it accesses this memory
991 This ioctl is required on Intel-based hosts. This is needed on Intel hardware
992 because of a quirk in the virtualization implementation (see the internals
993 documentation when it pops into existence).
998 Capability: KVM_CAP_ENABLE_CAP, KVM_CAP_ENABLE_CAP_VM
999 Architectures: x86 (only KVM_CAP_ENABLE_CAP_VM),
1000 mips (only KVM_CAP_ENABLE_CAP), ppc, s390
1001 Type: vcpu ioctl, vm ioctl (with KVM_CAP_ENABLE_CAP_VM)
1002 Parameters: struct kvm_enable_cap (in)
1003 Returns: 0 on success; -1 on error
1005 +Not all extensions are enabled by default. Using this ioctl the application
1006 can enable an extension, making it available to the guest.
1008 On systems that do not support this ioctl, it always fails. On systems that
1009 do support it, it only works for extensions that are supported for enablement.
1011 To check if a capability can be enabled, the KVM_CHECK_EXTENSION ioctl should
1014 struct kvm_enable_cap {
1018 The capability that is supposed to get enabled.
1022 A bitfield indicating future enhancements. Has to be 0 for now.
1026 Arguments for enabling a feature. If a feature needs initial values to
1027 function properly, this is the place to put them.
1032 The vcpu ioctl should be used for vcpu-specific capabilities, the vm ioctl
1033 for vm-wide capabilities.
1035 4.38 KVM_GET_MP_STATE
1037 Capability: KVM_CAP_MP_STATE
1038 Architectures: x86, s390, arm, arm64
1040 Parameters: struct kvm_mp_state (out)
1041 Returns: 0 on success; -1 on error
1043 struct kvm_mp_state {
1047 Returns the vcpu's current "multiprocessing state" (though also valid on
1048 uniprocessor guests).
1050 Possible values are:
1052 - KVM_MP_STATE_RUNNABLE: the vcpu is currently running [x86,arm/arm64]
1053 - KVM_MP_STATE_UNINITIALIZED: the vcpu is an application processor (AP)
1054 which has not yet received an INIT signal [x86]
1055 - KVM_MP_STATE_INIT_RECEIVED: the vcpu has received an INIT signal, and is
1056 now ready for a SIPI [x86]
1057 - KVM_MP_STATE_HALTED: the vcpu has executed a HLT instruction and
1058 is waiting for an interrupt [x86]
1059 - KVM_MP_STATE_SIPI_RECEIVED: the vcpu has just received a SIPI (vector
1060 accessible via KVM_GET_VCPU_EVENTS) [x86]
1061 - KVM_MP_STATE_STOPPED: the vcpu is stopped [s390,arm/arm64]
1062 - KVM_MP_STATE_CHECK_STOP: the vcpu is in a special error state [s390]
1063 - KVM_MP_STATE_OPERATING: the vcpu is operating (running or halted)
1065 - KVM_MP_STATE_LOAD: the vcpu is in a special load/startup state
1068 On x86, this ioctl is only useful after KVM_CREATE_IRQCHIP. Without an
1069 in-kernel irqchip, the multiprocessing state must be maintained by userspace on
1070 these architectures.
1074 The only states that are valid are KVM_MP_STATE_STOPPED and
1075 KVM_MP_STATE_RUNNABLE which reflect if the vcpu is paused or not.
1077 4.39 KVM_SET_MP_STATE
1079 Capability: KVM_CAP_MP_STATE
1080 Architectures: x86, s390, arm, arm64
1082 Parameters: struct kvm_mp_state (in)
1083 Returns: 0 on success; -1 on error
1085 Sets the vcpu's current "multiprocessing state"; see KVM_GET_MP_STATE for
1088 On x86, this ioctl is only useful after KVM_CREATE_IRQCHIP. Without an
1089 in-kernel irqchip, the multiprocessing state must be maintained by userspace on
1090 these architectures.
1094 The only states that are valid are KVM_MP_STATE_STOPPED and
1095 KVM_MP_STATE_RUNNABLE which reflect if the vcpu should be paused or not.
1097 4.40 KVM_SET_IDENTITY_MAP_ADDR
1099 Capability: KVM_CAP_SET_IDENTITY_MAP_ADDR
1102 Parameters: unsigned long identity (in)
1103 Returns: 0 on success, -1 on error
1105 This ioctl defines the physical address of a one-page region in the guest
1106 physical address space. The region must be within the first 4GB of the
1107 guest physical address space and must not conflict with any memory slot
1108 or any mmio address. The guest may malfunction if it accesses this memory
1111 This ioctl is required on Intel-based hosts. This is needed on Intel hardware
1112 because of a quirk in the virtualization implementation (see the internals
1113 documentation when it pops into existence).
1116 4.41 KVM_SET_BOOT_CPU_ID
1118 Capability: KVM_CAP_SET_BOOT_CPU_ID
1121 Parameters: unsigned long vcpu_id
1122 Returns: 0 on success, -1 on error
1124 Define which vcpu is the Bootstrap Processor (BSP). Values are the same
1125 as the vcpu id in KVM_CREATE_VCPU. If this ioctl is not called, the default
1131 Capability: KVM_CAP_XSAVE
1134 Parameters: struct kvm_xsave (out)
1135 Returns: 0 on success, -1 on error
1141 This ioctl would copy current vcpu's xsave struct to the userspace.
1146 Capability: KVM_CAP_XSAVE
1149 Parameters: struct kvm_xsave (in)
1150 Returns: 0 on success, -1 on error
1156 This ioctl would copy userspace's xsave struct to the kernel.
1161 Capability: KVM_CAP_XCRS
1164 Parameters: struct kvm_xcrs (out)
1165 Returns: 0 on success, -1 on error
1176 struct kvm_xcr xcrs[KVM_MAX_XCRS];
1180 This ioctl would copy current vcpu's xcrs to the userspace.
1185 Capability: KVM_CAP_XCRS
1188 Parameters: struct kvm_xcrs (in)
1189 Returns: 0 on success, -1 on error
1200 struct kvm_xcr xcrs[KVM_MAX_XCRS];
1204 This ioctl would set vcpu's xcr to the value userspace specified.
1207 4.46 KVM_GET_SUPPORTED_CPUID
1209 Capability: KVM_CAP_EXT_CPUID
1212 Parameters: struct kvm_cpuid2 (in/out)
1213 Returns: 0 on success, -1 on error
1218 struct kvm_cpuid_entry2 entries[0];
1221 #define KVM_CPUID_FLAG_SIGNIFCANT_INDEX BIT(0)
1222 #define KVM_CPUID_FLAG_STATEFUL_FUNC BIT(1)
1223 #define KVM_CPUID_FLAG_STATE_READ_NEXT BIT(2)
1225 struct kvm_cpuid_entry2 {
1236 This ioctl returns x86 cpuid features which are supported by both the hardware
1237 and kvm. Userspace can use the information returned by this ioctl to
1238 construct cpuid information (for KVM_SET_CPUID2) that is consistent with
1239 hardware, kernel, and userspace capabilities, and with user requirements (for
1240 example, the user may wish to constrain cpuid to emulate older hardware,
1241 or for feature consistency across a cluster).
1243 Userspace invokes KVM_GET_SUPPORTED_CPUID by passing a kvm_cpuid2 structure
1244 with the 'nent' field indicating the number of entries in the variable-size
1245 array 'entries'. If the number of entries is too low to describe the cpu
1246 capabilities, an error (E2BIG) is returned. If the number is too high,
1247 the 'nent' field is adjusted and an error (ENOMEM) is returned. If the
1248 number is just right, the 'nent' field is adjusted to the number of valid
1249 entries in the 'entries' array, which is then filled.
1251 The entries returned are the host cpuid as returned by the cpuid instruction,
1252 with unknown or unsupported features masked out. Some features (for example,
1253 x2apic), may not be present in the host cpu, but are exposed by kvm if it can
1254 emulate them efficiently. The fields in each entry are defined as follows:
1256 function: the eax value used to obtain the entry
1257 index: the ecx value used to obtain the entry (for entries that are
1259 flags: an OR of zero or more of the following:
1260 KVM_CPUID_FLAG_SIGNIFCANT_INDEX:
1261 if the index field is valid
1262 KVM_CPUID_FLAG_STATEFUL_FUNC:
1263 if cpuid for this function returns different values for successive
1264 invocations; there will be several entries with the same function,
1265 all with this flag set
1266 KVM_CPUID_FLAG_STATE_READ_NEXT:
1267 for KVM_CPUID_FLAG_STATEFUL_FUNC entries, set if this entry is
1268 the first entry to be read by a cpu
1269 eax, ebx, ecx, edx: the values returned by the cpuid instruction for
1270 this function/index combination
1272 The TSC deadline timer feature (CPUID leaf 1, ecx[24]) is always returned
1273 as false, since the feature depends on KVM_CREATE_IRQCHIP for local APIC
1274 support. Instead it is reported via
1276 ioctl(KVM_CHECK_EXTENSION, KVM_CAP_TSC_DEADLINE_TIMER)
1278 if that returns true and you use KVM_CREATE_IRQCHIP, or if you emulate the
1279 feature in userspace, then you can enable the feature for KVM_SET_CPUID2.
1282 4.47 KVM_PPC_GET_PVINFO
1284 Capability: KVM_CAP_PPC_GET_PVINFO
1287 Parameters: struct kvm_ppc_pvinfo (out)
1288 Returns: 0 on success, !0 on error
1290 struct kvm_ppc_pvinfo {
1296 This ioctl fetches PV specific information that need to be passed to the guest
1297 using the device tree or other means from vm context.
1299 The hcall array defines 4 instructions that make up a hypercall.
1301 If any additional field gets added to this structure later on, a bit for that
1302 additional piece of information will be set in the flags bitmap.
1304 The flags bitmap is defined as:
1306 /* the host supports the ePAPR idle hcall
1307 #define KVM_PPC_PVINFO_FLAGS_EV_IDLE (1<<0)
1309 4.48 KVM_ASSIGN_PCI_DEVICE (deprecated)
1314 Parameters: struct kvm_assigned_pci_dev (in)
1315 Returns: 0 on success, -1 on error
1317 Assigns a host PCI device to the VM.
1319 struct kvm_assigned_pci_dev {
1320 __u32 assigned_dev_id;
1330 The PCI device is specified by the triple segnr, busnr, and devfn.
1331 Identification in succeeding service requests is done via assigned_dev_id. The
1332 following flags are specified:
1334 /* Depends on KVM_CAP_IOMMU */
1335 #define KVM_DEV_ASSIGN_ENABLE_IOMMU (1 << 0)
1336 /* The following two depend on KVM_CAP_PCI_2_3 */
1337 #define KVM_DEV_ASSIGN_PCI_2_3 (1 << 1)
1338 #define KVM_DEV_ASSIGN_MASK_INTX (1 << 2)
1340 If KVM_DEV_ASSIGN_PCI_2_3 is set, the kernel will manage legacy INTx interrupts
1341 via the PCI-2.3-compliant device-level mask, thus enable IRQ sharing with other
1342 assigned devices or host devices. KVM_DEV_ASSIGN_MASK_INTX specifies the
1343 guest's view on the INTx mask, see KVM_ASSIGN_SET_INTX_MASK for details.
1345 The KVM_DEV_ASSIGN_ENABLE_IOMMU flag is a mandatory option to ensure
1346 isolation of the device. Usages not specifying this flag are deprecated.
1348 Only PCI header type 0 devices with PCI BAR resources are supported by
1349 device assignment. The user requesting this ioctl must have read/write
1350 access to the PCI sysfs resource files associated with the device.
1353 ENOTTY: kernel does not support this ioctl
1355 Other error conditions may be defined by individual device types or
1356 have their standard meanings.
1359 4.49 KVM_DEASSIGN_PCI_DEVICE (deprecated)
1364 Parameters: struct kvm_assigned_pci_dev (in)
1365 Returns: 0 on success, -1 on error
1367 Ends PCI device assignment, releasing all associated resources.
1369 See KVM_ASSIGN_PCI_DEVICE for the data structure. Only assigned_dev_id is
1370 used in kvm_assigned_pci_dev to identify the device.
1373 ENOTTY: kernel does not support this ioctl
1375 Other error conditions may be defined by individual device types or
1376 have their standard meanings.
1378 4.50 KVM_ASSIGN_DEV_IRQ (deprecated)
1380 Capability: KVM_CAP_ASSIGN_DEV_IRQ
1383 Parameters: struct kvm_assigned_irq (in)
1384 Returns: 0 on success, -1 on error
1386 Assigns an IRQ to a passed-through device.
1388 struct kvm_assigned_irq {
1389 __u32 assigned_dev_id;
1390 __u32 host_irq; /* ignored (legacy field) */
1398 The following flags are defined:
1400 #define KVM_DEV_IRQ_HOST_INTX (1 << 0)
1401 #define KVM_DEV_IRQ_HOST_MSI (1 << 1)
1402 #define KVM_DEV_IRQ_HOST_MSIX (1 << 2)
1404 #define KVM_DEV_IRQ_GUEST_INTX (1 << 8)
1405 #define KVM_DEV_IRQ_GUEST_MSI (1 << 9)
1406 #define KVM_DEV_IRQ_GUEST_MSIX (1 << 10)
1408 It is not valid to specify multiple types per host or guest IRQ. However, the
1409 IRQ type of host and guest can differ or can even be null.
1412 ENOTTY: kernel does not support this ioctl
1414 Other error conditions may be defined by individual device types or
1415 have their standard meanings.
1418 4.51 KVM_DEASSIGN_DEV_IRQ (deprecated)
1420 Capability: KVM_CAP_ASSIGN_DEV_IRQ
1423 Parameters: struct kvm_assigned_irq (in)
1424 Returns: 0 on success, -1 on error
1426 Ends an IRQ assignment to a passed-through device.
1428 See KVM_ASSIGN_DEV_IRQ for the data structure. The target device is specified
1429 by assigned_dev_id, flags must correspond to the IRQ type specified on
1430 KVM_ASSIGN_DEV_IRQ. Partial deassignment of host or guest IRQ is allowed.
1433 4.52 KVM_SET_GSI_ROUTING
1435 Capability: KVM_CAP_IRQ_ROUTING
1436 Architectures: x86 s390
1438 Parameters: struct kvm_irq_routing (in)
1439 Returns: 0 on success, -1 on error
1441 Sets the GSI routing table entries, overwriting any previously set entries.
1443 struct kvm_irq_routing {
1446 struct kvm_irq_routing_entry entries[0];
1449 No flags are specified so far, the corresponding field must be set to zero.
1451 struct kvm_irq_routing_entry {
1457 struct kvm_irq_routing_irqchip irqchip;
1458 struct kvm_irq_routing_msi msi;
1459 struct kvm_irq_routing_s390_adapter adapter;
1464 /* gsi routing entry types */
1465 #define KVM_IRQ_ROUTING_IRQCHIP 1
1466 #define KVM_IRQ_ROUTING_MSI 2
1467 #define KVM_IRQ_ROUTING_S390_ADAPTER 3
1469 No flags are specified so far, the corresponding field must be set to zero.
1471 struct kvm_irq_routing_irqchip {
1476 struct kvm_irq_routing_msi {
1483 struct kvm_irq_routing_s390_adapter {
1487 __u32 summary_offset;
1492 4.53 KVM_ASSIGN_SET_MSIX_NR (deprecated)
1497 Parameters: struct kvm_assigned_msix_nr (in)
1498 Returns: 0 on success, -1 on error
1500 Set the number of MSI-X interrupts for an assigned device. The number is
1501 reset again by terminating the MSI-X assignment of the device via
1502 KVM_DEASSIGN_DEV_IRQ. Calling this service more than once at any earlier
1505 struct kvm_assigned_msix_nr {
1506 __u32 assigned_dev_id;
1511 #define KVM_MAX_MSIX_PER_DEV 256
1514 4.54 KVM_ASSIGN_SET_MSIX_ENTRY (deprecated)
1519 Parameters: struct kvm_assigned_msix_entry (in)
1520 Returns: 0 on success, -1 on error
1522 Specifies the routing of an MSI-X assigned device interrupt to a GSI. Setting
1523 the GSI vector to zero means disabling the interrupt.
1525 struct kvm_assigned_msix_entry {
1526 __u32 assigned_dev_id;
1528 __u16 entry; /* The index of entry in the MSI-X table */
1533 ENOTTY: kernel does not support this ioctl
1535 Other error conditions may be defined by individual device types or
1536 have their standard meanings.
1539 4.55 KVM_SET_TSC_KHZ
1541 Capability: KVM_CAP_TSC_CONTROL
1544 Parameters: virtual tsc_khz
1545 Returns: 0 on success, -1 on error
1547 Specifies the tsc frequency for the virtual machine. The unit of the
1551 4.56 KVM_GET_TSC_KHZ
1553 Capability: KVM_CAP_GET_TSC_KHZ
1557 Returns: virtual tsc-khz on success, negative value on error
1559 Returns the tsc frequency of the guest. The unit of the return value is
1560 KHz. If the host has unstable tsc this ioctl returns -EIO instead as an
1566 Capability: KVM_CAP_IRQCHIP
1569 Parameters: struct kvm_lapic_state (out)
1570 Returns: 0 on success, -1 on error
1572 #define KVM_APIC_REG_SIZE 0x400
1573 struct kvm_lapic_state {
1574 char regs[KVM_APIC_REG_SIZE];
1577 Reads the Local APIC registers and copies them into the input argument. The
1578 data format and layout are the same as documented in the architecture manual.
1583 Capability: KVM_CAP_IRQCHIP
1586 Parameters: struct kvm_lapic_state (in)
1587 Returns: 0 on success, -1 on error
1589 #define KVM_APIC_REG_SIZE 0x400
1590 struct kvm_lapic_state {
1591 char regs[KVM_APIC_REG_SIZE];
1594 Copies the input argument into the Local APIC registers. The data format
1595 and layout are the same as documented in the architecture manual.
1600 Capability: KVM_CAP_IOEVENTFD
1603 Parameters: struct kvm_ioeventfd (in)
1604 Returns: 0 on success, !0 on error
1606 This ioctl attaches or detaches an ioeventfd to a legal pio/mmio address
1607 within the guest. A guest write in the registered address will signal the
1608 provided event instead of triggering an exit.
1610 struct kvm_ioeventfd {
1612 __u64 addr; /* legal pio/mmio address */
1613 __u32 len; /* 0, 1, 2, 4, or 8 bytes */
1619 For the special case of virtio-ccw devices on s390, the ioevent is matched
1620 to a subchannel/virtqueue tuple instead.
1622 The following flags are defined:
1624 #define KVM_IOEVENTFD_FLAG_DATAMATCH (1 << kvm_ioeventfd_flag_nr_datamatch)
1625 #define KVM_IOEVENTFD_FLAG_PIO (1 << kvm_ioeventfd_flag_nr_pio)
1626 #define KVM_IOEVENTFD_FLAG_DEASSIGN (1 << kvm_ioeventfd_flag_nr_deassign)
1627 #define KVM_IOEVENTFD_FLAG_VIRTIO_CCW_NOTIFY \
1628 (1 << kvm_ioeventfd_flag_nr_virtio_ccw_notify)
1630 If datamatch flag is set, the event will be signaled only if the written value
1631 to the registered address is equal to datamatch in struct kvm_ioeventfd.
1633 For virtio-ccw devices, addr contains the subchannel id and datamatch the
1636 With KVM_CAP_IOEVENTFD_ANY_LENGTH, a zero length ioeventfd is allowed, and
1637 the kernel will ignore the length of guest write and may get a faster vmexit.
1638 The speedup may only apply to specific architectures, but the ioeventfd will
1643 Capability: KVM_CAP_SW_TLB
1646 Parameters: struct kvm_dirty_tlb (in)
1647 Returns: 0 on success, -1 on error
1649 struct kvm_dirty_tlb {
1654 This must be called whenever userspace has changed an entry in the shared
1655 TLB, prior to calling KVM_RUN on the associated vcpu.
1657 The "bitmap" field is the userspace address of an array. This array
1658 consists of a number of bits, equal to the total number of TLB entries as
1659 determined by the last successful call to KVM_CONFIG_TLB, rounded up to the
1660 nearest multiple of 64.
1662 Each bit corresponds to one TLB entry, ordered the same as in the shared TLB
1665 The array is little-endian: the bit 0 is the least significant bit of the
1666 first byte, bit 8 is the least significant bit of the second byte, etc.
1667 This avoids any complications with differing word sizes.
1669 The "num_dirty" field is a performance hint for KVM to determine whether it
1670 should skip processing the bitmap and just invalidate everything. It must
1671 be set to the number of set bits in the bitmap.
1674 4.61 KVM_ASSIGN_SET_INTX_MASK (deprecated)
1676 Capability: KVM_CAP_PCI_2_3
1679 Parameters: struct kvm_assigned_pci_dev (in)
1680 Returns: 0 on success, -1 on error
1682 Allows userspace to mask PCI INTx interrupts from the assigned device. The
1683 kernel will not deliver INTx interrupts to the guest between setting and
1684 clearing of KVM_ASSIGN_SET_INTX_MASK via this interface. This enables use of
1685 and emulation of PCI 2.3 INTx disable command register behavior.
1687 This may be used for both PCI 2.3 devices supporting INTx disable natively and
1688 older devices lacking this support. Userspace is responsible for emulating the
1689 read value of the INTx disable bit in the guest visible PCI command register.
1690 When modifying the INTx disable state, userspace should precede updating the
1691 physical device command register by calling this ioctl to inform the kernel of
1692 the new intended INTx mask state.
1694 Note that the kernel uses the device INTx disable bit to internally manage the
1695 device interrupt state for PCI 2.3 devices. Reads of this register may
1696 therefore not match the expected value. Writes should always use the guest
1697 intended INTx disable value rather than attempting to read-copy-update the
1698 current physical device state. Races between user and kernel updates to the
1699 INTx disable bit are handled lazily in the kernel. It's possible the device
1700 may generate unintended interrupts, but they will not be injected into the
1703 See KVM_ASSIGN_DEV_IRQ for the data structure. The target device is specified
1704 by assigned_dev_id. In the flags field, only KVM_DEV_ASSIGN_MASK_INTX is
1708 4.62 KVM_CREATE_SPAPR_TCE
1710 Capability: KVM_CAP_SPAPR_TCE
1711 Architectures: powerpc
1713 Parameters: struct kvm_create_spapr_tce (in)
1714 Returns: file descriptor for manipulating the created TCE table
1716 This creates a virtual TCE (translation control entry) table, which
1717 is an IOMMU for PAPR-style virtual I/O. It is used to translate
1718 logical addresses used in virtual I/O into guest physical addresses,
1719 and provides a scatter/gather capability for PAPR virtual I/O.
1721 /* for KVM_CAP_SPAPR_TCE */
1722 struct kvm_create_spapr_tce {
1727 The liobn field gives the logical IO bus number for which to create a
1728 TCE table. The window_size field specifies the size of the DMA window
1729 which this TCE table will translate - the table will contain one 64
1730 bit TCE entry for every 4kiB of the DMA window.
1732 When the guest issues an H_PUT_TCE hcall on a liobn for which a TCE
1733 table has been created using this ioctl(), the kernel will handle it
1734 in real mode, updating the TCE table. H_PUT_TCE calls for other
1735 liobns will cause a vm exit and must be handled by userspace.
1737 The return value is a file descriptor which can be passed to mmap(2)
1738 to map the created TCE table into userspace. This lets userspace read
1739 the entries written by kernel-handled H_PUT_TCE calls, and also lets
1740 userspace update the TCE table directly which is useful in some
1744 4.63 KVM_ALLOCATE_RMA
1746 Capability: KVM_CAP_PPC_RMA
1747 Architectures: powerpc
1749 Parameters: struct kvm_allocate_rma (out)
1750 Returns: file descriptor for mapping the allocated RMA
1752 This allocates a Real Mode Area (RMA) from the pool allocated at boot
1753 time by the kernel. An RMA is a physically-contiguous, aligned region
1754 of memory used on older POWER processors to provide the memory which
1755 will be accessed by real-mode (MMU off) accesses in a KVM guest.
1756 POWER processors support a set of sizes for the RMA that usually
1757 includes 64MB, 128MB, 256MB and some larger powers of two.
1759 /* for KVM_ALLOCATE_RMA */
1760 struct kvm_allocate_rma {
1764 The return value is a file descriptor which can be passed to mmap(2)
1765 to map the allocated RMA into userspace. The mapped area can then be
1766 passed to the KVM_SET_USER_MEMORY_REGION ioctl to establish it as the
1767 RMA for a virtual machine. The size of the RMA in bytes (which is
1768 fixed at host kernel boot time) is returned in the rma_size field of
1769 the argument structure.
1771 The KVM_CAP_PPC_RMA capability is 1 or 2 if the KVM_ALLOCATE_RMA ioctl
1772 is supported; 2 if the processor requires all virtual machines to have
1773 an RMA, or 1 if the processor can use an RMA but doesn't require it,
1774 because it supports the Virtual RMA (VRMA) facility.
1779 Capability: KVM_CAP_USER_NMI
1783 Returns: 0 on success, -1 on error
1785 Queues an NMI on the thread's vcpu. Note this is well defined only
1786 when KVM_CREATE_IRQCHIP has not been called, since this is an interface
1787 between the virtual cpu core and virtual local APIC. After KVM_CREATE_IRQCHIP
1788 has been called, this interface is completely emulated within the kernel.
1790 To use this to emulate the LINT1 input with KVM_CREATE_IRQCHIP, use the
1791 following algorithm:
1794 - read the local APIC's state (KVM_GET_LAPIC)
1795 - check whether changing LINT1 will queue an NMI (see the LVT entry for LINT1)
1796 - if so, issue KVM_NMI
1799 Some guests configure the LINT1 NMI input to cause a panic, aiding in
1803 4.65 KVM_S390_UCAS_MAP
1805 Capability: KVM_CAP_S390_UCONTROL
1808 Parameters: struct kvm_s390_ucas_mapping (in)
1809 Returns: 0 in case of success
1811 The parameter is defined like this:
1812 struct kvm_s390_ucas_mapping {
1818 This ioctl maps the memory at "user_addr" with the length "length" to
1819 the vcpu's address space starting at "vcpu_addr". All parameters need to
1820 be aligned by 1 megabyte.
1823 4.66 KVM_S390_UCAS_UNMAP
1825 Capability: KVM_CAP_S390_UCONTROL
1828 Parameters: struct kvm_s390_ucas_mapping (in)
1829 Returns: 0 in case of success
1831 The parameter is defined like this:
1832 struct kvm_s390_ucas_mapping {
1838 This ioctl unmaps the memory in the vcpu's address space starting at
1839 "vcpu_addr" with the length "length". The field "user_addr" is ignored.
1840 All parameters need to be aligned by 1 megabyte.
1843 4.67 KVM_S390_VCPU_FAULT
1845 Capability: KVM_CAP_S390_UCONTROL
1848 Parameters: vcpu absolute address (in)
1849 Returns: 0 in case of success
1851 This call creates a page table entry on the virtual cpu's address space
1852 (for user controlled virtual machines) or the virtual machine's address
1853 space (for regular virtual machines). This only works for minor faults,
1854 thus it's recommended to access subject memory page via the user page
1855 table upfront. This is useful to handle validity intercepts for user
1856 controlled virtual machines to fault in the virtual cpu's lowcore pages
1857 prior to calling the KVM_RUN ioctl.
1860 4.68 KVM_SET_ONE_REG
1862 Capability: KVM_CAP_ONE_REG
1865 Parameters: struct kvm_one_reg (in)
1866 Returns: 0 on success, negative value on failure
1868 struct kvm_one_reg {
1873 Using this ioctl, a single vcpu register can be set to a specific value
1874 defined by user space with the passed in struct kvm_one_reg, where id
1875 refers to the register identifier as described below and addr is a pointer
1876 to a variable with the respective size. There can be architecture agnostic
1877 and architecture specific registers. Each have their own range of operation
1878 and their own constants and width. To keep track of the implemented
1879 registers, find a list below:
1881 Arch | Register | Width (bits)
1883 PPC | KVM_REG_PPC_HIOR | 64
1884 PPC | KVM_REG_PPC_IAC1 | 64
1885 PPC | KVM_REG_PPC_IAC2 | 64
1886 PPC | KVM_REG_PPC_IAC3 | 64
1887 PPC | KVM_REG_PPC_IAC4 | 64
1888 PPC | KVM_REG_PPC_DAC1 | 64
1889 PPC | KVM_REG_PPC_DAC2 | 64
1890 PPC | KVM_REG_PPC_DABR | 64
1891 PPC | KVM_REG_PPC_DSCR | 64
1892 PPC | KVM_REG_PPC_PURR | 64
1893 PPC | KVM_REG_PPC_SPURR | 64
1894 PPC | KVM_REG_PPC_DAR | 64
1895 PPC | KVM_REG_PPC_DSISR | 32
1896 PPC | KVM_REG_PPC_AMR | 64
1897 PPC | KVM_REG_PPC_UAMOR | 64
1898 PPC | KVM_REG_PPC_MMCR0 | 64
1899 PPC | KVM_REG_PPC_MMCR1 | 64
1900 PPC | KVM_REG_PPC_MMCRA | 64
1901 PPC | KVM_REG_PPC_MMCR2 | 64
1902 PPC | KVM_REG_PPC_MMCRS | 64
1903 PPC | KVM_REG_PPC_SIAR | 64
1904 PPC | KVM_REG_PPC_SDAR | 64
1905 PPC | KVM_REG_PPC_SIER | 64
1906 PPC | KVM_REG_PPC_PMC1 | 32
1907 PPC | KVM_REG_PPC_PMC2 | 32
1908 PPC | KVM_REG_PPC_PMC3 | 32
1909 PPC | KVM_REG_PPC_PMC4 | 32
1910 PPC | KVM_REG_PPC_PMC5 | 32
1911 PPC | KVM_REG_PPC_PMC6 | 32
1912 PPC | KVM_REG_PPC_PMC7 | 32
1913 PPC | KVM_REG_PPC_PMC8 | 32
1914 PPC | KVM_REG_PPC_FPR0 | 64
1916 PPC | KVM_REG_PPC_FPR31 | 64
1917 PPC | KVM_REG_PPC_VR0 | 128
1919 PPC | KVM_REG_PPC_VR31 | 128
1920 PPC | KVM_REG_PPC_VSR0 | 128
1922 PPC | KVM_REG_PPC_VSR31 | 128
1923 PPC | KVM_REG_PPC_FPSCR | 64
1924 PPC | KVM_REG_PPC_VSCR | 32
1925 PPC | KVM_REG_PPC_VPA_ADDR | 64
1926 PPC | KVM_REG_PPC_VPA_SLB | 128
1927 PPC | KVM_REG_PPC_VPA_DTL | 128
1928 PPC | KVM_REG_PPC_EPCR | 32
1929 PPC | KVM_REG_PPC_EPR | 32
1930 PPC | KVM_REG_PPC_TCR | 32
1931 PPC | KVM_REG_PPC_TSR | 32
1932 PPC | KVM_REG_PPC_OR_TSR | 32
1933 PPC | KVM_REG_PPC_CLEAR_TSR | 32
1934 PPC | KVM_REG_PPC_MAS0 | 32
1935 PPC | KVM_REG_PPC_MAS1 | 32
1936 PPC | KVM_REG_PPC_MAS2 | 64
1937 PPC | KVM_REG_PPC_MAS7_3 | 64
1938 PPC | KVM_REG_PPC_MAS4 | 32
1939 PPC | KVM_REG_PPC_MAS6 | 32
1940 PPC | KVM_REG_PPC_MMUCFG | 32
1941 PPC | KVM_REG_PPC_TLB0CFG | 32
1942 PPC | KVM_REG_PPC_TLB1CFG | 32
1943 PPC | KVM_REG_PPC_TLB2CFG | 32
1944 PPC | KVM_REG_PPC_TLB3CFG | 32
1945 PPC | KVM_REG_PPC_TLB0PS | 32
1946 PPC | KVM_REG_PPC_TLB1PS | 32
1947 PPC | KVM_REG_PPC_TLB2PS | 32
1948 PPC | KVM_REG_PPC_TLB3PS | 32
1949 PPC | KVM_REG_PPC_EPTCFG | 32
1950 PPC | KVM_REG_PPC_ICP_STATE | 64
1951 PPC | KVM_REG_PPC_TB_OFFSET | 64
1952 PPC | KVM_REG_PPC_SPMC1 | 32
1953 PPC | KVM_REG_PPC_SPMC2 | 32
1954 PPC | KVM_REG_PPC_IAMR | 64
1955 PPC | KVM_REG_PPC_TFHAR | 64
1956 PPC | KVM_REG_PPC_TFIAR | 64
1957 PPC | KVM_REG_PPC_TEXASR | 64
1958 PPC | KVM_REG_PPC_FSCR | 64
1959 PPC | KVM_REG_PPC_PSPB | 32
1960 PPC | KVM_REG_PPC_EBBHR | 64
1961 PPC | KVM_REG_PPC_EBBRR | 64
1962 PPC | KVM_REG_PPC_BESCR | 64
1963 PPC | KVM_REG_PPC_TAR | 64
1964 PPC | KVM_REG_PPC_DPDES | 64
1965 PPC | KVM_REG_PPC_DAWR | 64
1966 PPC | KVM_REG_PPC_DAWRX | 64
1967 PPC | KVM_REG_PPC_CIABR | 64
1968 PPC | KVM_REG_PPC_IC | 64
1969 PPC | KVM_REG_PPC_VTB | 64
1970 PPC | KVM_REG_PPC_CSIGR | 64
1971 PPC | KVM_REG_PPC_TACR | 64
1972 PPC | KVM_REG_PPC_TCSCR | 64
1973 PPC | KVM_REG_PPC_PID | 64
1974 PPC | KVM_REG_PPC_ACOP | 64
1975 PPC | KVM_REG_PPC_VRSAVE | 32
1976 PPC | KVM_REG_PPC_LPCR | 32
1977 PPC | KVM_REG_PPC_LPCR_64 | 64
1978 PPC | KVM_REG_PPC_PPR | 64
1979 PPC | KVM_REG_PPC_ARCH_COMPAT | 32
1980 PPC | KVM_REG_PPC_DABRX | 32
1981 PPC | KVM_REG_PPC_WORT | 64
1982 PPC | KVM_REG_PPC_SPRG9 | 64
1983 PPC | KVM_REG_PPC_DBSR | 32
1984 PPC | KVM_REG_PPC_TM_GPR0 | 64
1986 PPC | KVM_REG_PPC_TM_GPR31 | 64
1987 PPC | KVM_REG_PPC_TM_VSR0 | 128
1989 PPC | KVM_REG_PPC_TM_VSR63 | 128
1990 PPC | KVM_REG_PPC_TM_CR | 64
1991 PPC | KVM_REG_PPC_TM_LR | 64
1992 PPC | KVM_REG_PPC_TM_CTR | 64
1993 PPC | KVM_REG_PPC_TM_FPSCR | 64
1994 PPC | KVM_REG_PPC_TM_AMR | 64
1995 PPC | KVM_REG_PPC_TM_PPR | 64
1996 PPC | KVM_REG_PPC_TM_VRSAVE | 64
1997 PPC | KVM_REG_PPC_TM_VSCR | 32
1998 PPC | KVM_REG_PPC_TM_DSCR | 64
1999 PPC | KVM_REG_PPC_TM_TAR | 64
2000 PPC | KVM_REG_PPC_TM_XER | 64
2002 MIPS | KVM_REG_MIPS_R0 | 64
2004 MIPS | KVM_REG_MIPS_R31 | 64
2005 MIPS | KVM_REG_MIPS_HI | 64
2006 MIPS | KVM_REG_MIPS_LO | 64
2007 MIPS | KVM_REG_MIPS_PC | 64
2008 MIPS | KVM_REG_MIPS_CP0_INDEX | 32
2009 MIPS | KVM_REG_MIPS_CP0_CONTEXT | 64
2010 MIPS | KVM_REG_MIPS_CP0_USERLOCAL | 64
2011 MIPS | KVM_REG_MIPS_CP0_PAGEMASK | 32
2012 MIPS | KVM_REG_MIPS_CP0_WIRED | 32
2013 MIPS | KVM_REG_MIPS_CP0_HWRENA | 32
2014 MIPS | KVM_REG_MIPS_CP0_BADVADDR | 64
2015 MIPS | KVM_REG_MIPS_CP0_COUNT | 32
2016 MIPS | KVM_REG_MIPS_CP0_ENTRYHI | 64
2017 MIPS | KVM_REG_MIPS_CP0_COMPARE | 32
2018 MIPS | KVM_REG_MIPS_CP0_STATUS | 32
2019 MIPS | KVM_REG_MIPS_CP0_CAUSE | 32
2020 MIPS | KVM_REG_MIPS_CP0_EPC | 64
2021 MIPS | KVM_REG_MIPS_CP0_PRID | 32
2022 MIPS | KVM_REG_MIPS_CP0_CONFIG | 32
2023 MIPS | KVM_REG_MIPS_CP0_CONFIG1 | 32
2024 MIPS | KVM_REG_MIPS_CP0_CONFIG2 | 32
2025 MIPS | KVM_REG_MIPS_CP0_CONFIG3 | 32
2026 MIPS | KVM_REG_MIPS_CP0_CONFIG4 | 32
2027 MIPS | KVM_REG_MIPS_CP0_CONFIG5 | 32
2028 MIPS | KVM_REG_MIPS_CP0_CONFIG7 | 32
2029 MIPS | KVM_REG_MIPS_CP0_ERROREPC | 64
2030 MIPS | KVM_REG_MIPS_COUNT_CTL | 64
2031 MIPS | KVM_REG_MIPS_COUNT_RESUME | 64
2032 MIPS | KVM_REG_MIPS_COUNT_HZ | 64
2033 MIPS | KVM_REG_MIPS_FPR_32(0..31) | 32
2034 MIPS | KVM_REG_MIPS_FPR_64(0..31) | 64
2035 MIPS | KVM_REG_MIPS_VEC_128(0..31) | 128
2036 MIPS | KVM_REG_MIPS_FCR_IR | 32
2037 MIPS | KVM_REG_MIPS_FCR_CSR | 32
2038 MIPS | KVM_REG_MIPS_MSA_IR | 32
2039 MIPS | KVM_REG_MIPS_MSA_CSR | 32
2041 ARM registers are mapped using the lower 32 bits. The upper 16 of that
2042 is the register group type, or coprocessor number:
2044 ARM core registers have the following id bit patterns:
2045 0x4020 0000 0010 <index into the kvm_regs struct:16>
2047 ARM 32-bit CP15 registers have the following id bit patterns:
2048 0x4020 0000 000F <zero:1> <crn:4> <crm:4> <opc1:4> <opc2:3>
2050 ARM 64-bit CP15 registers have the following id bit patterns:
2051 0x4030 0000 000F <zero:1> <zero:4> <crm:4> <opc1:4> <zero:3>
2053 ARM CCSIDR registers are demultiplexed by CSSELR value:
2054 0x4020 0000 0011 00 <csselr:8>
2056 ARM 32-bit VFP control registers have the following id bit patterns:
2057 0x4020 0000 0012 1 <regno:12>
2059 ARM 64-bit FP registers have the following id bit patterns:
2060 0x4030 0000 0012 0 <regno:12>
2063 arm64 registers are mapped using the lower 32 bits. The upper 16 of
2064 that is the register group type, or coprocessor number:
2066 arm64 core/FP-SIMD registers have the following id bit patterns. Note
2067 that the size of the access is variable, as the kvm_regs structure
2068 contains elements ranging from 32 to 128 bits. The index is a 32bit
2069 value in the kvm_regs structure seen as a 32bit array.
2070 0x60x0 0000 0010 <index into the kvm_regs struct:16>
2072 arm64 CCSIDR registers are demultiplexed by CSSELR value:
2073 0x6020 0000 0011 00 <csselr:8>
2075 arm64 system registers have the following id bit patterns:
2076 0x6030 0000 0013 <op0:2> <op1:3> <crn:4> <crm:4> <op2:3>
2079 MIPS registers are mapped using the lower 32 bits. The upper 16 of that is
2080 the register group type:
2082 MIPS core registers (see above) have the following id bit patterns:
2083 0x7030 0000 0000 <reg:16>
2085 MIPS CP0 registers (see KVM_REG_MIPS_CP0_* above) have the following id bit
2086 patterns depending on whether they're 32-bit or 64-bit registers:
2087 0x7020 0000 0001 00 <reg:5> <sel:3> (32-bit)
2088 0x7030 0000 0001 00 <reg:5> <sel:3> (64-bit)
2090 MIPS KVM control registers (see above) have the following id bit patterns:
2091 0x7030 0000 0002 <reg:16>
2093 MIPS FPU registers (see KVM_REG_MIPS_FPR_{32,64}() above) have the following
2094 id bit patterns depending on the size of the register being accessed. They are
2095 always accessed according to the current guest FPU mode (Status.FR and
2096 Config5.FRE), i.e. as the guest would see them, and they become unpredictable
2097 if the guest FPU mode is changed. MIPS SIMD Architecture (MSA) vector
2098 registers (see KVM_REG_MIPS_VEC_128() above) have similar patterns as they
2099 overlap the FPU registers:
2100 0x7020 0000 0003 00 <0:3> <reg:5> (32-bit FPU registers)
2101 0x7030 0000 0003 00 <0:3> <reg:5> (64-bit FPU registers)
2102 0x7040 0000 0003 00 <0:3> <reg:5> (128-bit MSA vector registers)
2104 MIPS FPU control registers (see KVM_REG_MIPS_FCR_{IR,CSR} above) have the
2105 following id bit patterns:
2106 0x7020 0000 0003 01 <0:3> <reg:5>
2108 MIPS MSA control registers (see KVM_REG_MIPS_MSA_{IR,CSR} above) have the
2109 following id bit patterns:
2110 0x7020 0000 0003 02 <0:3> <reg:5>
2113 4.69 KVM_GET_ONE_REG
2115 Capability: KVM_CAP_ONE_REG
2118 Parameters: struct kvm_one_reg (in and out)
2119 Returns: 0 on success, negative value on failure
2121 This ioctl allows to receive the value of a single register implemented
2122 in a vcpu. The register to read is indicated by the "id" field of the
2123 kvm_one_reg struct passed in. On success, the register value can be found
2124 at the memory location pointed to by "addr".
2126 The list of registers accessible using this interface is identical to the
2130 4.70 KVM_KVMCLOCK_CTRL
2132 Capability: KVM_CAP_KVMCLOCK_CTRL
2133 Architectures: Any that implement pvclocks (currently x86 only)
2136 Returns: 0 on success, -1 on error
2138 This signals to the host kernel that the specified guest is being paused by
2139 userspace. The host will set a flag in the pvclock structure that is checked
2140 from the soft lockup watchdog. The flag is part of the pvclock structure that
2141 is shared between guest and host, specifically the second bit of the flags
2142 field of the pvclock_vcpu_time_info structure. It will be set exclusively by
2143 the host and read/cleared exclusively by the guest. The guest operation of
2144 checking and clearing the flag must an atomic operation so
2145 load-link/store-conditional, or equivalent must be used. There are two cases
2146 where the guest will clear the flag: when the soft lockup watchdog timer resets
2147 itself or when a soft lockup is detected. This ioctl can be called any time
2148 after pausing the vcpu, but before it is resumed.
2153 Capability: KVM_CAP_SIGNAL_MSI
2156 Parameters: struct kvm_msi (in)
2157 Returns: >0 on delivery, 0 if guest blocked the MSI, and -1 on error
2159 Directly inject a MSI message. Only valid with in-kernel irqchip that handles
2170 No flags are defined so far. The corresponding field must be 0.
2173 4.71 KVM_CREATE_PIT2
2175 Capability: KVM_CAP_PIT2
2178 Parameters: struct kvm_pit_config (in)
2179 Returns: 0 on success, -1 on error
2181 Creates an in-kernel device model for the i8254 PIT. This call is only valid
2182 after enabling in-kernel irqchip support via KVM_CREATE_IRQCHIP. The following
2183 parameters have to be passed:
2185 struct kvm_pit_config {
2192 #define KVM_PIT_SPEAKER_DUMMY 1 /* emulate speaker port stub */
2194 PIT timer interrupts may use a per-VM kernel thread for injection. If it
2195 exists, this thread will have a name of the following pattern:
2197 kvm-pit/<owner-process-pid>
2199 When running a guest with elevated priorities, the scheduling parameters of
2200 this thread may have to be adjusted accordingly.
2202 This IOCTL replaces the obsolete KVM_CREATE_PIT.
2207 Capability: KVM_CAP_PIT_STATE2
2210 Parameters: struct kvm_pit_state2 (out)
2211 Returns: 0 on success, -1 on error
2213 Retrieves the state of the in-kernel PIT model. Only valid after
2214 KVM_CREATE_PIT2. The state is returned in the following structure:
2216 struct kvm_pit_state2 {
2217 struct kvm_pit_channel_state channels[3];
2224 /* disable PIT in HPET legacy mode */
2225 #define KVM_PIT_FLAGS_HPET_LEGACY 0x00000001
2227 This IOCTL replaces the obsolete KVM_GET_PIT.
2232 Capability: KVM_CAP_PIT_STATE2
2235 Parameters: struct kvm_pit_state2 (in)
2236 Returns: 0 on success, -1 on error
2238 Sets the state of the in-kernel PIT model. Only valid after KVM_CREATE_PIT2.
2239 See KVM_GET_PIT2 for details on struct kvm_pit_state2.
2241 This IOCTL replaces the obsolete KVM_SET_PIT.
2244 4.74 KVM_PPC_GET_SMMU_INFO
2246 Capability: KVM_CAP_PPC_GET_SMMU_INFO
2247 Architectures: powerpc
2250 Returns: 0 on success, -1 on error
2252 This populates and returns a structure describing the features of
2253 the "Server" class MMU emulation supported by KVM.
2254 This can in turn be used by userspace to generate the appropriate
2255 device-tree properties for the guest operating system.
2257 The structure contains some global information, followed by an
2258 array of supported segment page sizes:
2260 struct kvm_ppc_smmu_info {
2264 struct kvm_ppc_one_seg_page_size sps[KVM_PPC_PAGE_SIZES_MAX_SZ];
2267 The supported flags are:
2269 - KVM_PPC_PAGE_SIZES_REAL:
2270 When that flag is set, guest page sizes must "fit" the backing
2271 store page sizes. When not set, any page size in the list can
2272 be used regardless of how they are backed by userspace.
2274 - KVM_PPC_1T_SEGMENTS
2275 The emulated MMU supports 1T segments in addition to the
2278 The "slb_size" field indicates how many SLB entries are supported
2280 The "sps" array contains 8 entries indicating the supported base
2281 page sizes for a segment in increasing order. Each entry is defined
2284 struct kvm_ppc_one_seg_page_size {
2285 __u32 page_shift; /* Base page shift of segment (or 0) */
2286 __u32 slb_enc; /* SLB encoding for BookS */
2287 struct kvm_ppc_one_page_size enc[KVM_PPC_PAGE_SIZES_MAX_SZ];
2290 An entry with a "page_shift" of 0 is unused. Because the array is
2291 organized in increasing order, a lookup can stop when encoutering
2294 The "slb_enc" field provides the encoding to use in the SLB for the
2295 page size. The bits are in positions such as the value can directly
2296 be OR'ed into the "vsid" argument of the slbmte instruction.
2298 The "enc" array is a list which for each of those segment base page
2299 size provides the list of supported actual page sizes (which can be
2300 only larger or equal to the base page size), along with the
2301 corresponding encoding in the hash PTE. Similarly, the array is
2302 8 entries sorted by increasing sizes and an entry with a "0" shift
2303 is an empty entry and a terminator:
2305 struct kvm_ppc_one_page_size {
2306 __u32 page_shift; /* Page shift (or 0) */
2307 __u32 pte_enc; /* Encoding in the HPTE (>>12) */
2310 The "pte_enc" field provides a value that can OR'ed into the hash
2311 PTE's RPN field (ie, it needs to be shifted left by 12 to OR it
2312 into the hash PTE second double word).
2316 Capability: KVM_CAP_IRQFD
2317 Architectures: x86 s390 arm arm64
2319 Parameters: struct kvm_irqfd (in)
2320 Returns: 0 on success, -1 on error
2322 Allows setting an eventfd to directly trigger a guest interrupt.
2323 kvm_irqfd.fd specifies the file descriptor to use as the eventfd and
2324 kvm_irqfd.gsi specifies the irqchip pin toggled by this event. When
2325 an event is triggered on the eventfd, an interrupt is injected into
2326 the guest using the specified gsi pin. The irqfd is removed using
2327 the KVM_IRQFD_FLAG_DEASSIGN flag, specifying both kvm_irqfd.fd
2330 With KVM_CAP_IRQFD_RESAMPLE, KVM_IRQFD supports a de-assert and notify
2331 mechanism allowing emulation of level-triggered, irqfd-based
2332 interrupts. When KVM_IRQFD_FLAG_RESAMPLE is set the user must pass an
2333 additional eventfd in the kvm_irqfd.resamplefd field. When operating
2334 in resample mode, posting of an interrupt through kvm_irq.fd asserts
2335 the specified gsi in the irqchip. When the irqchip is resampled, such
2336 as from an EOI, the gsi is de-asserted and the user is notified via
2337 kvm_irqfd.resamplefd. It is the user's responsibility to re-queue
2338 the interrupt if the device making use of it still requires service.
2339 Note that closing the resamplefd is not sufficient to disable the
2340 irqfd. The KVM_IRQFD_FLAG_RESAMPLE is only necessary on assignment
2341 and need not be specified with KVM_IRQFD_FLAG_DEASSIGN.
2343 On ARM/ARM64, the gsi field in the kvm_irqfd struct specifies the Shared
2344 Peripheral Interrupt (SPI) index, such that the GIC interrupt ID is
2347 4.76 KVM_PPC_ALLOCATE_HTAB
2349 Capability: KVM_CAP_PPC_ALLOC_HTAB
2350 Architectures: powerpc
2352 Parameters: Pointer to u32 containing hash table order (in/out)
2353 Returns: 0 on success, -1 on error
2355 This requests the host kernel to allocate an MMU hash table for a
2356 guest using the PAPR paravirtualization interface. This only does
2357 anything if the kernel is configured to use the Book 3S HV style of
2358 virtualization. Otherwise the capability doesn't exist and the ioctl
2359 returns an ENOTTY error. The rest of this description assumes Book 3S
2362 There must be no vcpus running when this ioctl is called; if there
2363 are, it will do nothing and return an EBUSY error.
2365 The parameter is a pointer to a 32-bit unsigned integer variable
2366 containing the order (log base 2) of the desired size of the hash
2367 table, which must be between 18 and 46. On successful return from the
2368 ioctl, it will have been updated with the order of the hash table that
2371 If no hash table has been allocated when any vcpu is asked to run
2372 (with the KVM_RUN ioctl), the host kernel will allocate a
2373 default-sized hash table (16 MB).
2375 If this ioctl is called when a hash table has already been allocated,
2376 the kernel will clear out the existing hash table (zero all HPTEs) and
2377 return the hash table order in the parameter. (If the guest is using
2378 the virtualized real-mode area (VRMA) facility, the kernel will
2379 re-create the VMRA HPTEs on the next KVM_RUN of any vcpu.)
2381 4.77 KVM_S390_INTERRUPT
2385 Type: vm ioctl, vcpu ioctl
2386 Parameters: struct kvm_s390_interrupt (in)
2387 Returns: 0 on success, -1 on error
2389 Allows to inject an interrupt to the guest. Interrupts can be floating
2390 (vm ioctl) or per cpu (vcpu ioctl), depending on the interrupt type.
2392 Interrupt parameters are passed via kvm_s390_interrupt:
2394 struct kvm_s390_interrupt {
2400 type can be one of the following:
2402 KVM_S390_SIGP_STOP (vcpu) - sigp stop; optional flags in parm
2403 KVM_S390_PROGRAM_INT (vcpu) - program check; code in parm
2404 KVM_S390_SIGP_SET_PREFIX (vcpu) - sigp set prefix; prefix address in parm
2405 KVM_S390_RESTART (vcpu) - restart
2406 KVM_S390_INT_CLOCK_COMP (vcpu) - clock comparator interrupt
2407 KVM_S390_INT_CPU_TIMER (vcpu) - CPU timer interrupt
2408 KVM_S390_INT_VIRTIO (vm) - virtio external interrupt; external interrupt
2409 parameters in parm and parm64
2410 KVM_S390_INT_SERVICE (vm) - sclp external interrupt; sclp parameter in parm
2411 KVM_S390_INT_EMERGENCY (vcpu) - sigp emergency; source cpu in parm
2412 KVM_S390_INT_EXTERNAL_CALL (vcpu) - sigp external call; source cpu in parm
2413 KVM_S390_INT_IO(ai,cssid,ssid,schid) (vm) - compound value to indicate an
2414 I/O interrupt (ai - adapter interrupt; cssid,ssid,schid - subchannel);
2415 I/O interruption parameters in parm (subchannel) and parm64 (intparm,
2416 interruption subclass)
2417 KVM_S390_MCHK (vm, vcpu) - machine check interrupt; cr 14 bits in parm,
2418 machine check interrupt code in parm64 (note that
2419 machine checks needing further payload are not
2420 supported by this ioctl)
2422 Note that the vcpu ioctl is asynchronous to vcpu execution.
2424 4.78 KVM_PPC_GET_HTAB_FD
2426 Capability: KVM_CAP_PPC_HTAB_FD
2427 Architectures: powerpc
2429 Parameters: Pointer to struct kvm_get_htab_fd (in)
2430 Returns: file descriptor number (>= 0) on success, -1 on error
2432 This returns a file descriptor that can be used either to read out the
2433 entries in the guest's hashed page table (HPT), or to write entries to
2434 initialize the HPT. The returned fd can only be written to if the
2435 KVM_GET_HTAB_WRITE bit is set in the flags field of the argument, and
2436 can only be read if that bit is clear. The argument struct looks like
2439 /* For KVM_PPC_GET_HTAB_FD */
2440 struct kvm_get_htab_fd {
2446 /* Values for kvm_get_htab_fd.flags */
2447 #define KVM_GET_HTAB_BOLTED_ONLY ((__u64)0x1)
2448 #define KVM_GET_HTAB_WRITE ((__u64)0x2)
2450 The `start_index' field gives the index in the HPT of the entry at
2451 which to start reading. It is ignored when writing.
2453 Reads on the fd will initially supply information about all
2454 "interesting" HPT entries. Interesting entries are those with the
2455 bolted bit set, if the KVM_GET_HTAB_BOLTED_ONLY bit is set, otherwise
2456 all entries. When the end of the HPT is reached, the read() will
2457 return. If read() is called again on the fd, it will start again from
2458 the beginning of the HPT, but will only return HPT entries that have
2459 changed since they were last read.
2461 Data read or written is structured as a header (8 bytes) followed by a
2462 series of valid HPT entries (16 bytes) each. The header indicates how
2463 many valid HPT entries there are and how many invalid entries follow
2464 the valid entries. The invalid entries are not represented explicitly
2465 in the stream. The header format is:
2467 struct kvm_get_htab_header {
2473 Writes to the fd create HPT entries starting at the index given in the
2474 header; first `n_valid' valid entries with contents from the data
2475 written, then `n_invalid' invalid entries, invalidating any previously
2476 valid entries found.
2478 4.79 KVM_CREATE_DEVICE
2480 Capability: KVM_CAP_DEVICE_CTRL
2482 Parameters: struct kvm_create_device (in/out)
2483 Returns: 0 on success, -1 on error
2485 ENODEV: The device type is unknown or unsupported
2486 EEXIST: Device already created, and this type of device may not
2487 be instantiated multiple times
2489 Other error conditions may be defined by individual device types or
2490 have their standard meanings.
2492 Creates an emulated device in the kernel. The file descriptor returned
2493 in fd can be used with KVM_SET/GET/HAS_DEVICE_ATTR.
2495 If the KVM_CREATE_DEVICE_TEST flag is set, only test whether the
2496 device type is supported (not necessarily whether it can be created
2499 Individual devices should not define flags. Attributes should be used
2500 for specifying any behavior that is not implied by the device type
2503 struct kvm_create_device {
2504 __u32 type; /* in: KVM_DEV_TYPE_xxx */
2505 __u32 fd; /* out: device handle */
2506 __u32 flags; /* in: KVM_CREATE_DEVICE_xxx */
2509 4.80 KVM_SET_DEVICE_ATTR/KVM_GET_DEVICE_ATTR
2511 Capability: KVM_CAP_DEVICE_CTRL, KVM_CAP_VM_ATTRIBUTES for vm device
2512 Type: device ioctl, vm ioctl
2513 Parameters: struct kvm_device_attr
2514 Returns: 0 on success, -1 on error
2516 ENXIO: The group or attribute is unknown/unsupported for this device
2517 EPERM: The attribute cannot (currently) be accessed this way
2518 (e.g. read-only attribute, or attribute that only makes
2519 sense when the device is in a different state)
2521 Other error conditions may be defined by individual device types.
2523 Gets/sets a specified piece of device configuration and/or state. The
2524 semantics are device-specific. See individual device documentation in
2525 the "devices" directory. As with ONE_REG, the size of the data
2526 transferred is defined by the particular attribute.
2528 struct kvm_device_attr {
2529 __u32 flags; /* no flags currently defined */
2530 __u32 group; /* device-defined */
2531 __u64 attr; /* group-defined */
2532 __u64 addr; /* userspace address of attr data */
2535 4.81 KVM_HAS_DEVICE_ATTR
2537 Capability: KVM_CAP_DEVICE_CTRL, KVM_CAP_VM_ATTRIBUTES for vm device
2538 Type: device ioctl, vm ioctl
2539 Parameters: struct kvm_device_attr
2540 Returns: 0 on success, -1 on error
2542 ENXIO: The group or attribute is unknown/unsupported for this device
2544 Tests whether a device supports a particular attribute. A successful
2545 return indicates the attribute is implemented. It does not necessarily
2546 indicate that the attribute can be read or written in the device's
2547 current state. "addr" is ignored.
2549 4.82 KVM_ARM_VCPU_INIT
2552 Architectures: arm, arm64
2554 Parameters: struct kvm_vcpu_init (in)
2555 Returns: 0 on success; -1 on error
2557 Â EINVAL: Â Â Â the target is unknown, or the combination of features is invalid.
2558 Â ENOENT: Â Â Â a features bit specified is unknown.
2560 This tells KVM what type of CPU to present to the guest, and what
2561 optional features it should have. Â This will cause a reset of the cpu
2562 registers to their initial values. Â If this is not called, KVM_RUN will
2563 return ENOEXEC for that vcpu.
2565 Note that because some registers reflect machine topology, all vcpus
2566 should be created before this ioctl is invoked.
2568 Userspace can call this function multiple times for a given vcpu, including
2569 after the vcpu has been run. This will reset the vcpu to its initial
2570 state. All calls to this function after the initial call must use the same
2571 target and same set of feature flags, otherwise EINVAL will be returned.
2574 - KVM_ARM_VCPU_POWER_OFF: Starts the CPU in a power-off state.
2575 Depends on KVM_CAP_ARM_PSCI. If not set, the CPU will be powered on
2576 and execute guest code when KVM_RUN is called.
2577 - KVM_ARM_VCPU_EL1_32BIT: Starts the CPU in a 32bit mode.
2578 Depends on KVM_CAP_ARM_EL1_32BIT (arm64 only).
2579 - KVM_ARM_VCPU_PSCI_0_2: Emulate PSCI v0.2 for the CPU.
2580 Depends on KVM_CAP_ARM_PSCI_0_2.
2583 4.83 KVM_ARM_PREFERRED_TARGET
2586 Architectures: arm, arm64
2588 Parameters: struct struct kvm_vcpu_init (out)
2589 Returns: 0 on success; -1 on error
2591 ENODEV: no preferred target available for the host
2593 This queries KVM for preferred CPU target type which can be emulated
2594 by KVM on underlying host.
2596 The ioctl returns struct kvm_vcpu_init instance containing information
2597 about preferred CPU target type and recommended features for it. The
2598 kvm_vcpu_init->features bitmap returned will have feature bits set if
2599 the preferred target recommends setting these features, but this is
2602 The information returned by this ioctl can be used to prepare an instance
2603 of struct kvm_vcpu_init for KVM_ARM_VCPU_INIT ioctl which will result in
2604 in VCPU matching underlying host.
2607 4.84 KVM_GET_REG_LIST
2610 Architectures: arm, arm64, mips
2612 Parameters: struct kvm_reg_list (in/out)
2613 Returns: 0 on success; -1 on error
2615 Â E2BIG: Â Â Â Â the reg index list is too big to fit in the array specified by
2616 Â Â Â Â Â Â Â Â Â Â Â Â the user (the number required will be written into n).
2618 struct kvm_reg_list {
2619 __u64 n; /* number of registers in reg[] */
2623 This ioctl returns the guest registers that are supported for the
2624 KVM_GET_ONE_REG/KVM_SET_ONE_REG calls.
2627 4.85 KVM_ARM_SET_DEVICE_ADDR (deprecated)
2629 Capability: KVM_CAP_ARM_SET_DEVICE_ADDR
2630 Architectures: arm, arm64
2632 Parameters: struct kvm_arm_device_address (in)
2633 Returns: 0 on success, -1 on error
2635 ENODEV: The device id is unknown
2636 ENXIO: Device not supported on current system
2637 EEXIST: Address already set
2638 E2BIG: Address outside guest physical address space
2639 EBUSY: Address overlaps with other device range
2641 struct kvm_arm_device_addr {
2646 Specify a device address in the guest's physical address space where guests
2647 can access emulated or directly exposed devices, which the host kernel needs
2648 to know about. The id field is an architecture specific identifier for a
2651 ARM/arm64 divides the id field into two parts, a device id and an
2652 address type id specific to the individual device.
2654 Â bits: | 63 ... 32 | 31 ... 16 | 15 ... 0 |
2655 field: | 0x00000000 | device id | addr type id |
2657 ARM/arm64 currently only require this when using the in-kernel GIC
2658 support for the hardware VGIC features, using KVM_ARM_DEVICE_VGIC_V2
2659 as the device id. When setting the base address for the guest's
2660 mapping of the VGIC virtual CPU and distributor interface, the ioctl
2661 must be called after calling KVM_CREATE_IRQCHIP, but before calling
2662 KVM_RUN on any of the VCPUs. Calling this ioctl twice for any of the
2663 base addresses will return -EEXIST.
2665 Note, this IOCTL is deprecated and the more flexible SET/GET_DEVICE_ATTR API
2666 should be used instead.
2669 4.86 KVM_PPC_RTAS_DEFINE_TOKEN
2671 Capability: KVM_CAP_PPC_RTAS
2674 Parameters: struct kvm_rtas_token_args
2675 Returns: 0 on success, -1 on error
2677 Defines a token value for a RTAS (Run Time Abstraction Services)
2678 service in order to allow it to be handled in the kernel. The
2679 argument struct gives the name of the service, which must be the name
2680 of a service that has a kernel-side implementation. If the token
2681 value is non-zero, it will be associated with that service, and
2682 subsequent RTAS calls by the guest specifying that token will be
2683 handled by the kernel. If the token value is 0, then any token
2684 associated with the service will be forgotten, and subsequent RTAS
2685 calls by the guest for that service will be passed to userspace to be
2688 4.87 KVM_SET_GUEST_DEBUG
2690 Capability: KVM_CAP_SET_GUEST_DEBUG
2691 Architectures: x86, s390, ppc, arm64
2693 Parameters: struct kvm_guest_debug (in)
2694 Returns: 0 on success; -1 on error
2696 struct kvm_guest_debug {
2699 struct kvm_guest_debug_arch arch;
2702 Set up the processor specific debug registers and configure vcpu for
2703 handling guest debug events. There are two parts to the structure, the
2704 first a control bitfield indicates the type of debug events to handle
2705 when running. Common control bits are:
2707 - KVM_GUESTDBG_ENABLE: guest debugging is enabled
2708 - KVM_GUESTDBG_SINGLESTEP: the next run should single-step
2710 The top 16 bits of the control field are architecture specific control
2711 flags which can include the following:
2713 - KVM_GUESTDBG_USE_SW_BP: using software breakpoints [x86, arm64]
2714 - KVM_GUESTDBG_USE_HW_BP: using hardware breakpoints [x86, s390, arm64]
2715 - KVM_GUESTDBG_INJECT_DB: inject DB type exception [x86]
2716 - KVM_GUESTDBG_INJECT_BP: inject BP type exception [x86]
2717 - KVM_GUESTDBG_EXIT_PENDING: trigger an immediate guest exit [s390]
2719 For example KVM_GUESTDBG_USE_SW_BP indicates that software breakpoints
2720 are enabled in memory so we need to ensure breakpoint exceptions are
2721 correctly trapped and the KVM run loop exits at the breakpoint and not
2722 running off into the normal guest vector. For KVM_GUESTDBG_USE_HW_BP
2723 we need to ensure the guest vCPUs architecture specific registers are
2724 updated to the correct (supplied) values.
2726 The second part of the structure is architecture specific and
2727 typically contains a set of debug registers.
2729 For arm64 the number of debug registers is implementation defined and
2730 can be determined by querying the KVM_CAP_GUEST_DEBUG_HW_BPS and
2731 KVM_CAP_GUEST_DEBUG_HW_WPS capabilities which return a positive number
2732 indicating the number of supported registers.
2734 When debug events exit the main run loop with the reason
2735 KVM_EXIT_DEBUG with the kvm_debug_exit_arch part of the kvm_run
2736 structure containing architecture specific debug information.
2738 4.88 KVM_GET_EMULATED_CPUID
2740 Capability: KVM_CAP_EXT_EMUL_CPUID
2743 Parameters: struct kvm_cpuid2 (in/out)
2744 Returns: 0 on success, -1 on error
2749 struct kvm_cpuid_entry2 entries[0];
2752 The member 'flags' is used for passing flags from userspace.
2754 #define KVM_CPUID_FLAG_SIGNIFCANT_INDEX BIT(0)
2755 #define KVM_CPUID_FLAG_STATEFUL_FUNC BIT(1)
2756 #define KVM_CPUID_FLAG_STATE_READ_NEXT BIT(2)
2758 struct kvm_cpuid_entry2 {
2769 This ioctl returns x86 cpuid features which are emulated by
2770 kvm.Userspace can use the information returned by this ioctl to query
2771 which features are emulated by kvm instead of being present natively.
2773 Userspace invokes KVM_GET_EMULATED_CPUID by passing a kvm_cpuid2
2774 structure with the 'nent' field indicating the number of entries in
2775 the variable-size array 'entries'. If the number of entries is too low
2776 to describe the cpu capabilities, an error (E2BIG) is returned. If the
2777 number is too high, the 'nent' field is adjusted and an error (ENOMEM)
2778 is returned. If the number is just right, the 'nent' field is adjusted
2779 to the number of valid entries in the 'entries' array, which is then
2782 The entries returned are the set CPUID bits of the respective features
2783 which kvm emulates, as returned by the CPUID instruction, with unknown
2784 or unsupported feature bits cleared.
2786 Features like x2apic, for example, may not be present in the host cpu
2787 but are exposed by kvm in KVM_GET_SUPPORTED_CPUID because they can be
2788 emulated efficiently and thus not included here.
2790 The fields in each entry are defined as follows:
2792 function: the eax value used to obtain the entry
2793 index: the ecx value used to obtain the entry (for entries that are
2795 flags: an OR of zero or more of the following:
2796 KVM_CPUID_FLAG_SIGNIFCANT_INDEX:
2797 if the index field is valid
2798 KVM_CPUID_FLAG_STATEFUL_FUNC:
2799 if cpuid for this function returns different values for successive
2800 invocations; there will be several entries with the same function,
2801 all with this flag set
2802 KVM_CPUID_FLAG_STATE_READ_NEXT:
2803 for KVM_CPUID_FLAG_STATEFUL_FUNC entries, set if this entry is
2804 the first entry to be read by a cpu
2805 eax, ebx, ecx, edx: the values returned by the cpuid instruction for
2806 this function/index combination
2808 4.89 KVM_S390_MEM_OP
2810 Capability: KVM_CAP_S390_MEM_OP
2813 Parameters: struct kvm_s390_mem_op (in)
2814 Returns: = 0 on success,
2815 < 0 on generic error (e.g. -EFAULT or -ENOMEM),
2816 > 0 if an exception occurred while walking the page tables
2818 Read or write data from/to the logical (virtual) memory of a VCPU.
2820 Parameters are specified via the following structure:
2822 struct kvm_s390_mem_op {
2823 __u64 gaddr; /* the guest address */
2824 __u64 flags; /* flags */
2825 __u32 size; /* amount of bytes */
2826 __u32 op; /* type of operation */
2827 __u64 buf; /* buffer in userspace */
2828 __u8 ar; /* the access register number */
2829 __u8 reserved[31]; /* should be set to 0 */
2832 The type of operation is specified in the "op" field. It is either
2833 KVM_S390_MEMOP_LOGICAL_READ for reading from logical memory space or
2834 KVM_S390_MEMOP_LOGICAL_WRITE for writing to logical memory space. The
2835 KVM_S390_MEMOP_F_CHECK_ONLY flag can be set in the "flags" field to check
2836 whether the corresponding memory access would create an access exception
2837 (without touching the data in the memory at the destination). In case an
2838 access exception occurred while walking the MMU tables of the guest, the
2839 ioctl returns a positive error number to indicate the type of exception.
2840 This exception is also raised directly at the corresponding VCPU if the
2841 flag KVM_S390_MEMOP_F_INJECT_EXCEPTION is set in the "flags" field.
2843 The start address of the memory region has to be specified in the "gaddr"
2844 field, and the length of the region in the "size" field. "buf" is the buffer
2845 supplied by the userspace application where the read data should be written
2846 to for KVM_S390_MEMOP_LOGICAL_READ, or where the data that should be written
2847 is stored for a KVM_S390_MEMOP_LOGICAL_WRITE. "buf" is unused and can be NULL
2848 when KVM_S390_MEMOP_F_CHECK_ONLY is specified. "ar" designates the access
2849 register number to be used.
2851 The "reserved" field is meant for future extensions. It is not used by
2852 KVM with the currently defined set of flags.
2854 4.90 KVM_S390_GET_SKEYS
2856 Capability: KVM_CAP_S390_SKEYS
2859 Parameters: struct kvm_s390_skeys
2860 Returns: 0 on success, KVM_S390_GET_KEYS_NONE if guest is not using storage
2861 keys, negative value on error
2863 This ioctl is used to get guest storage key values on the s390
2864 architecture. The ioctl takes parameters via the kvm_s390_skeys struct.
2866 struct kvm_s390_skeys {
2869 __u64 skeydata_addr;
2874 The start_gfn field is the number of the first guest frame whose storage keys
2877 The count field is the number of consecutive frames (starting from start_gfn)
2878 whose storage keys to get. The count field must be at least 1 and the maximum
2879 allowed value is defined as KVM_S390_SKEYS_ALLOC_MAX. Values outside this range
2880 will cause the ioctl to return -EINVAL.
2882 The skeydata_addr field is the address to a buffer large enough to hold count
2883 bytes. This buffer will be filled with storage key data by the ioctl.
2885 4.91 KVM_S390_SET_SKEYS
2887 Capability: KVM_CAP_S390_SKEYS
2890 Parameters: struct kvm_s390_skeys
2891 Returns: 0 on success, negative value on error
2893 This ioctl is used to set guest storage key values on the s390
2894 architecture. The ioctl takes parameters via the kvm_s390_skeys struct.
2895 See section on KVM_S390_GET_SKEYS for struct definition.
2897 The start_gfn field is the number of the first guest frame whose storage keys
2900 The count field is the number of consecutive frames (starting from start_gfn)
2901 whose storage keys to get. The count field must be at least 1 and the maximum
2902 allowed value is defined as KVM_S390_SKEYS_ALLOC_MAX. Values outside this range
2903 will cause the ioctl to return -EINVAL.
2905 The skeydata_addr field is the address to a buffer containing count bytes of
2906 storage keys. Each byte in the buffer will be set as the storage key for a
2907 single frame starting at start_gfn for count frames.
2909 Note: If any architecturally invalid key value is found in the given data then
2910 the ioctl will return -EINVAL.
2914 Capability: KVM_CAP_S390_INJECT_IRQ
2917 Parameters: struct kvm_s390_irq (in)
2918 Returns: 0 on success, -1 on error
2920 EINVAL: interrupt type is invalid
2921 type is KVM_S390_SIGP_STOP and flag parameter is invalid value
2922 type is KVM_S390_INT_EXTERNAL_CALL and code is bigger
2923 than the maximum of VCPUs
2924 EBUSY: type is KVM_S390_SIGP_SET_PREFIX and vcpu is not stopped
2925 type is KVM_S390_SIGP_STOP and a stop irq is already pending
2926 type is KVM_S390_INT_EXTERNAL_CALL and an external call interrupt
2929 Allows to inject an interrupt to the guest.
2931 Using struct kvm_s390_irq as a parameter allows
2932 to inject additional payload which is not
2933 possible via KVM_S390_INTERRUPT.
2935 Interrupt parameters are passed via kvm_s390_irq:
2937 struct kvm_s390_irq {
2940 struct kvm_s390_io_info io;
2941 struct kvm_s390_ext_info ext;
2942 struct kvm_s390_pgm_info pgm;
2943 struct kvm_s390_emerg_info emerg;
2944 struct kvm_s390_extcall_info extcall;
2945 struct kvm_s390_prefix_info prefix;
2946 struct kvm_s390_stop_info stop;
2947 struct kvm_s390_mchk_info mchk;
2952 type can be one of the following:
2954 KVM_S390_SIGP_STOP - sigp stop; parameter in .stop
2955 KVM_S390_PROGRAM_INT - program check; parameters in .pgm
2956 KVM_S390_SIGP_SET_PREFIX - sigp set prefix; parameters in .prefix
2957 KVM_S390_RESTART - restart; no parameters
2958 KVM_S390_INT_CLOCK_COMP - clock comparator interrupt; no parameters
2959 KVM_S390_INT_CPU_TIMER - CPU timer interrupt; no parameters
2960 KVM_S390_INT_EMERGENCY - sigp emergency; parameters in .emerg
2961 KVM_S390_INT_EXTERNAL_CALL - sigp external call; parameters in .extcall
2962 KVM_S390_MCHK - machine check interrupt; parameters in .mchk
2965 Note that the vcpu ioctl is asynchronous to vcpu execution.
2967 4.94 KVM_S390_GET_IRQ_STATE
2969 Capability: KVM_CAP_S390_IRQ_STATE
2972 Parameters: struct kvm_s390_irq_state (out)
2973 Returns: >= number of bytes copied into buffer,
2974 -EINVAL if buffer size is 0,
2975 -ENOBUFS if buffer size is too small to fit all pending interrupts,
2976 -EFAULT if the buffer address was invalid
2978 This ioctl allows userspace to retrieve the complete state of all currently
2979 pending interrupts in a single buffer. Use cases include migration
2980 and introspection. The parameter structure contains the address of a
2981 userspace buffer and its length:
2983 struct kvm_s390_irq_state {
2990 Userspace passes in the above struct and for each pending interrupt a
2991 struct kvm_s390_irq is copied to the provided buffer.
2993 If -ENOBUFS is returned the buffer provided was too small and userspace
2994 may retry with a bigger buffer.
2996 4.95 KVM_S390_SET_IRQ_STATE
2998 Capability: KVM_CAP_S390_IRQ_STATE
3001 Parameters: struct kvm_s390_irq_state (in)
3002 Returns: 0 on success,
3003 -EFAULT if the buffer address was invalid,
3004 -EINVAL for an invalid buffer length (see below),
3005 -EBUSY if there were already interrupts pending,
3006 errors occurring when actually injecting the
3007 interrupt. See KVM_S390_IRQ.
3009 This ioctl allows userspace to set the complete state of all cpu-local
3010 interrupts currently pending for the vcpu. It is intended for restoring
3011 interrupt state after a migration. The input parameter is a userspace buffer
3012 containing a struct kvm_s390_irq_state:
3014 struct kvm_s390_irq_state {
3020 The userspace memory referenced by buf contains a struct kvm_s390_irq
3021 for each interrupt to be injected into the guest.
3022 If one of the interrupts could not be injected for some reason the
3025 len must be a multiple of sizeof(struct kvm_s390_irq). It must be > 0
3026 and it must not exceed (max_vcpus + 32) * sizeof(struct kvm_s390_irq),
3027 which is the maximum number of possibly pending cpu-local interrupts.
3031 Capability: KVM_CAP_X86_SMM
3035 Returns: 0 on success, -1 on error
3037 Queues an SMI on the thread's vcpu.
3039 5. The kvm_run structure
3040 ------------------------
3042 Application code obtains a pointer to the kvm_run structure by
3043 mmap()ing a vcpu fd. From that point, application code can control
3044 execution by changing fields in kvm_run prior to calling the KVM_RUN
3045 ioctl, and obtain information about the reason KVM_RUN returned by
3046 looking up structure members.
3050 __u8 request_interrupt_window;
3052 Request that KVM_RUN return when it becomes possible to inject external
3053 interrupts into the guest. Useful in conjunction with KVM_INTERRUPT.
3060 When KVM_RUN has returned successfully (return value 0), this informs
3061 application code why KVM_RUN has returned. Allowable values for this
3062 field are detailed below.
3064 __u8 ready_for_interrupt_injection;
3066 If request_interrupt_window has been specified, this field indicates
3067 an interrupt can be injected now with KVM_INTERRUPT.
3071 The value of the current interrupt flag. Only valid if in-kernel
3072 local APIC is not used.
3076 More architecture-specific flags detailing state of the VCPU that may
3077 affect the device's behavior. The only currently defined flag is
3078 KVM_RUN_X86_SMM, which is valid on x86 machines and is set if the
3079 VCPU is in system management mode.
3081 /* in (pre_kvm_run), out (post_kvm_run) */
3084 The value of the cr8 register. Only valid if in-kernel local APIC is
3085 not used. Both input and output.
3089 The value of the APIC BASE msr. Only valid if in-kernel local
3090 APIC is not used. Both input and output.
3093 /* KVM_EXIT_UNKNOWN */
3095 __u64 hardware_exit_reason;
3098 If exit_reason is KVM_EXIT_UNKNOWN, the vcpu has exited due to unknown
3099 reasons. Further architecture-specific information is available in
3100 hardware_exit_reason.
3102 /* KVM_EXIT_FAIL_ENTRY */
3104 __u64 hardware_entry_failure_reason;
3107 If exit_reason is KVM_EXIT_FAIL_ENTRY, the vcpu could not be run due
3108 to unknown reasons. Further architecture-specific information is
3109 available in hardware_entry_failure_reason.
3111 /* KVM_EXIT_EXCEPTION */
3121 #define KVM_EXIT_IO_IN 0
3122 #define KVM_EXIT_IO_OUT 1
3124 __u8 size; /* bytes */
3127 __u64 data_offset; /* relative to kvm_run start */
3130 If exit_reason is KVM_EXIT_IO, then the vcpu has
3131 executed a port I/O instruction which could not be satisfied by kvm.
3132 data_offset describes where the data is located (KVM_EXIT_IO_OUT) or
3133 where kvm expects application code to place the data for the next
3134 KVM_RUN invocation (KVM_EXIT_IO_IN). Data format is a packed array.
3136 /* KVM_EXIT_DEBUG */
3138 struct kvm_debug_exit_arch arch;
3141 If the exit_reason is KVM_EXIT_DEBUG, then a vcpu is processing a debug event
3142 for which architecture specific information is returned.
3152 If exit_reason is KVM_EXIT_MMIO, then the vcpu has
3153 executed a memory-mapped I/O instruction which could not be satisfied
3154 by kvm. The 'data' member contains the written data if 'is_write' is
3155 true, and should be filled by application code otherwise.
3157 The 'data' member contains, in its first 'len' bytes, the value as it would
3158 appear if the VCPU performed a load or store of the appropriate width directly
3161 NOTE: For KVM_EXIT_IO, KVM_EXIT_MMIO, KVM_EXIT_OSI, KVM_EXIT_PAPR and
3162 KVM_EXIT_EPR the corresponding
3163 operations are complete (and guest state is consistent) only after userspace
3164 has re-entered the kernel with KVM_RUN. The kernel side will first finish
3165 incomplete operations and then check for pending signals. Userspace
3166 can re-enter the guest with an unmasked signal pending to complete
3169 /* KVM_EXIT_HYPERCALL */
3178 Unused. This was once used for 'hypercall to userspace'. To implement
3179 such functionality, use KVM_EXIT_IO (x86) or KVM_EXIT_MMIO (all except s390).
3180 Note KVM_EXIT_IO is significantly faster than KVM_EXIT_MMIO.
3182 /* KVM_EXIT_TPR_ACCESS */
3189 To be documented (KVM_TPR_ACCESS_REPORTING).
3191 /* KVM_EXIT_S390_SIEIC */
3194 __u64 mask; /* psw upper half */
3195 __u64 addr; /* psw lower half */
3202 /* KVM_EXIT_S390_RESET */
3203 #define KVM_S390_RESET_POR 1
3204 #define KVM_S390_RESET_CLEAR 2
3205 #define KVM_S390_RESET_SUBSYSTEM 4
3206 #define KVM_S390_RESET_CPU_INIT 8
3207 #define KVM_S390_RESET_IPL 16
3208 __u64 s390_reset_flags;
3212 /* KVM_EXIT_S390_UCONTROL */
3214 __u64 trans_exc_code;
3218 s390 specific. A page fault has occurred for a user controlled virtual
3219 machine (KVM_VM_S390_UNCONTROL) on it's host page table that cannot be
3220 resolved by the kernel.
3221 The program code and the translation exception code that were placed
3222 in the cpu's lowcore are presented here as defined by the z Architecture
3223 Principles of Operation Book in the Chapter for Dynamic Address Translation
3233 Deprecated - was used for 440 KVM.
3240 MOL uses a special hypercall interface it calls 'OSI'. To enable it, we catch
3241 hypercalls and exit with this exit struct that contains all the guest gprs.
3243 If exit_reason is KVM_EXIT_OSI, then the vcpu has triggered such a hypercall.
3244 Userspace can now handle the hypercall and when it's done modify the gprs as
3245 necessary. Upon guest entry all guest GPRs will then be replaced by the values
3248 /* KVM_EXIT_PAPR_HCALL */
3255 This is used on 64-bit PowerPC when emulating a pSeries partition,
3256 e.g. with the 'pseries' machine type in qemu. It occurs when the
3257 guest does a hypercall using the 'sc 1' instruction. The 'nr' field
3258 contains the hypercall number (from the guest R3), and 'args' contains
3259 the arguments (from the guest R4 - R12). Userspace should put the
3260 return code in 'ret' and any extra returned values in args[].
3261 The possible hypercalls are defined in the Power Architecture Platform
3262 Requirements (PAPR) document available from www.power.org (free
3263 developer registration required to access it).
3265 /* KVM_EXIT_S390_TSCH */
3267 __u16 subchannel_id;
3268 __u16 subchannel_nr;
3275 s390 specific. This exit occurs when KVM_CAP_S390_CSS_SUPPORT has been enabled
3276 and TEST SUBCHANNEL was intercepted. If dequeued is set, a pending I/O
3277 interrupt for the target subchannel has been dequeued and subchannel_id,
3278 subchannel_nr, io_int_parm and io_int_word contain the parameters for that
3279 interrupt. ipb is needed for instruction parameter decoding.
3286 On FSL BookE PowerPC chips, the interrupt controller has a fast patch
3287 interrupt acknowledge path to the core. When the core successfully
3288 delivers an interrupt, it automatically populates the EPR register with
3289 the interrupt vector number and acknowledges the interrupt inside
3290 the interrupt controller.
3292 In case the interrupt controller lives in user space, we need to do
3293 the interrupt acknowledge cycle through it to fetch the next to be
3294 delivered interrupt vector using this exit.
3296 It gets triggered whenever both KVM_CAP_PPC_EPR are enabled and an
3297 external interrupt has just been delivered into the guest. User space
3298 should put the acknowledged interrupt vector into the 'epr' field.
3300 /* KVM_EXIT_SYSTEM_EVENT */
3302 #define KVM_SYSTEM_EVENT_SHUTDOWN 1
3303 #define KVM_SYSTEM_EVENT_RESET 2
3304 #define KVM_SYSTEM_EVENT_CRASH 3
3309 If exit_reason is KVM_EXIT_SYSTEM_EVENT then the vcpu has triggered
3310 a system-level event using some architecture specific mechanism (hypercall
3311 or some special instruction). In case of ARM/ARM64, this is triggered using
3312 HVC instruction based PSCI call from the vcpu. The 'type' field describes
3313 the system-level event type. The 'flags' field describes architecture
3314 specific flags for the system-level event.
3316 Valid values for 'type' are:
3317 KVM_SYSTEM_EVENT_SHUTDOWN -- the guest has requested a shutdown of the
3318 VM. Userspace is not obliged to honour this, and if it does honour
3319 this does not need to destroy the VM synchronously (ie it may call
3320 KVM_RUN again before shutdown finally occurs).
3321 KVM_SYSTEM_EVENT_RESET -- the guest has requested a reset of the VM.
3322 As with SHUTDOWN, userspace can choose to ignore the request, or
3323 to schedule the reset to occur in the future and may call KVM_RUN again.
3324 KVM_SYSTEM_EVENT_CRASH -- the guest crash occurred and the guest
3325 has requested a crash condition maintenance. Userspace can choose
3326 to ignore the request, or to gather VM memory core dump and/or
3327 reset/shutdown of the VM.
3329 /* KVM_EXIT_IOAPIC_EOI */
3334 Indicates that the VCPU's in-kernel local APIC received an EOI for a
3335 level-triggered IOAPIC interrupt. This exit only triggers when the
3336 IOAPIC is implemented in userspace (i.e. KVM_CAP_SPLIT_IRQCHIP is enabled);
3337 the userspace IOAPIC should process the EOI and retrigger the interrupt if
3338 it is still asserted. Vector is the LAPIC interrupt vector for which the
3341 /* Fix the size of the union. */
3346 * shared registers between kvm and userspace.
3347 * kvm_valid_regs specifies the register classes set by the host
3348 * kvm_dirty_regs specified the register classes dirtied by userspace
3349 * struct kvm_sync_regs is architecture specific, as well as the
3350 * bits for kvm_valid_regs and kvm_dirty_regs
3352 __u64 kvm_valid_regs;
3353 __u64 kvm_dirty_regs;
3355 struct kvm_sync_regs regs;
3359 If KVM_CAP_SYNC_REGS is defined, these fields allow userspace to access
3360 certain guest registers without having to call SET/GET_*REGS. Thus we can
3361 avoid some system call overhead if userspace has to handle the exit.
3362 Userspace can query the validity of the structure by checking
3363 kvm_valid_regs for specific bits. These bits are architecture specific
3364 and usually define the validity of a groups of registers. (e.g. one bit
3365 for general purpose registers)
3367 Please note that the kernel is allowed to use the kvm_run structure as the
3368 primary storage for certain register types. Therefore, the kernel may use the
3369 values in kvm_run even if the corresponding bit in kvm_dirty_regs is not set.
3375 6. Capabilities that can be enabled on vCPUs
3376 --------------------------------------------
3378 There are certain capabilities that change the behavior of the virtual CPU or
3379 the virtual machine when enabled. To enable them, please see section 4.37.
3380 Below you can find a list of capabilities and what their effect on the vCPU or
3381 the virtual machine is when enabling them.
3383 The following information is provided along with the description:
3385 Architectures: which instruction set architectures provide this ioctl.
3386 x86 includes both i386 and x86_64.
3388 Target: whether this is a per-vcpu or per-vm capability.
3390 Parameters: what parameters are accepted by the capability.
3392 Returns: the return value. General error numbers (EBADF, ENOMEM, EINVAL)
3393 are not detailed, but errors with specific meanings are.
3401 Returns: 0 on success; -1 on error
3403 This capability enables interception of OSI hypercalls that otherwise would
3404 be treated as normal system calls to be injected into the guest. OSI hypercalls
3405 were invented by Mac-on-Linux to have a standardized communication mechanism
3406 between the guest and the host.
3408 When this capability is enabled, KVM_EXIT_OSI can occur.
3411 6.2 KVM_CAP_PPC_PAPR
3416 Returns: 0 on success; -1 on error
3418 This capability enables interception of PAPR hypercalls. PAPR hypercalls are
3419 done using the hypercall instruction "sc 1".
3421 It also sets the guest privilege level to "supervisor" mode. Usually the guest
3422 runs in "hypervisor" privilege mode with a few missing features.
3424 In addition to the above, it changes the semantics of SDR1. In this mode, the
3425 HTAB address part of SDR1 contains an HVA instead of a GPA, as PAPR keeps the
3426 HTAB invisible to the guest.
3428 When this capability is enabled, KVM_EXIT_PAPR_HCALL can occur.
3435 Parameters: args[0] is the address of a struct kvm_config_tlb
3436 Returns: 0 on success; -1 on error
3438 struct kvm_config_tlb {
3445 Configures the virtual CPU's TLB array, establishing a shared memory area
3446 between userspace and KVM. The "params" and "array" fields are userspace
3447 addresses of mmu-type-specific data structures. The "array_len" field is an
3448 safety mechanism, and should be set to the size in bytes of the memory that
3449 userspace has reserved for the array. It must be at least the size dictated
3450 by "mmu_type" and "params".
3452 While KVM_RUN is active, the shared region is under control of KVM. Its
3453 contents are undefined, and any modification by userspace results in
3454 boundedly undefined behavior.
3456 On return from KVM_RUN, the shared region will reflect the current state of
3457 the guest's TLB. If userspace makes any changes, it must call KVM_DIRTY_TLB
3458 to tell KVM which entries have been changed, prior to calling KVM_RUN again
3461 For mmu types KVM_MMU_FSL_BOOKE_NOHV and KVM_MMU_FSL_BOOKE_HV:
3462 - The "params" field is of type "struct kvm_book3e_206_tlb_params".
3463 - The "array" field points to an array of type "struct
3464 kvm_book3e_206_tlb_entry".
3465 - The array consists of all entries in the first TLB, followed by all
3466 entries in the second TLB.
3467 - Within a TLB, entries are ordered first by increasing set number. Within a
3468 set, entries are ordered by way (increasing ESEL).
3469 - The hash for determining set number in TLB0 is: (MAS2 >> 12) & (num_sets - 1)
3470 where "num_sets" is the tlb_sizes[] value divided by the tlb_ways[] value.
3471 - The tsize field of mas1 shall be set to 4K on TLB0, even though the
3472 hardware ignores this value for TLB0.
3474 6.4 KVM_CAP_S390_CSS_SUPPORT
3479 Returns: 0 on success; -1 on error
3481 This capability enables support for handling of channel I/O instructions.
3483 TEST PENDING INTERRUPTION and the interrupt portion of TEST SUBCHANNEL are
3484 handled in-kernel, while the other I/O instructions are passed to userspace.
3486 When this capability is enabled, KVM_EXIT_S390_TSCH will occur on TEST
3487 SUBCHANNEL intercepts.
3489 Note that even though this capability is enabled per-vcpu, the complete
3490 virtual machine is affected.
3496 Parameters: args[0] defines whether the proxy facility is active
3497 Returns: 0 on success; -1 on error
3499 This capability enables or disables the delivery of interrupts through the
3500 external proxy facility.
3502 When enabled (args[0] != 0), every time the guest gets an external interrupt
3503 delivered, it automatically exits into user space with a KVM_EXIT_EPR exit
3504 to receive the topmost interrupt vector.
3506 When disabled (args[0] == 0), behavior is as if this facility is unsupported.
3508 When this capability is enabled, KVM_EXIT_EPR can occur.
3510 6.6 KVM_CAP_IRQ_MPIC
3513 Parameters: args[0] is the MPIC device fd
3514 args[1] is the MPIC CPU number for this vcpu
3516 This capability connects the vcpu to an in-kernel MPIC device.
3518 6.7 KVM_CAP_IRQ_XICS
3522 Parameters: args[0] is the XICS device fd
3523 args[1] is the XICS CPU number (server ID) for this vcpu
3525 This capability connects the vcpu to an in-kernel XICS device.
3527 6.8 KVM_CAP_S390_IRQCHIP
3533 This capability enables the in-kernel irqchip for s390. Please refer to
3534 "4.24 KVM_CREATE_IRQCHIP" for details.
3536 6.9 KVM_CAP_MIPS_FPU
3540 Parameters: args[0] is reserved for future use (should be 0).
3542 This capability allows the use of the host Floating Point Unit by the guest. It
3543 allows the Config1.FP bit to be set to enable the FPU in the guest. Once this is
3544 done the KVM_REG_MIPS_FPR_* and KVM_REG_MIPS_FCR_* registers can be accessed
3545 (depending on the current guest FPU register mode), and the Status.FR,
3546 Config5.FRE bits are accessible via the KVM API and also from the guest,
3547 depending on them being supported by the FPU.
3549 6.10 KVM_CAP_MIPS_MSA
3553 Parameters: args[0] is reserved for future use (should be 0).
3555 This capability allows the use of the MIPS SIMD Architecture (MSA) by the guest.
3556 It allows the Config3.MSAP bit to be set to enable the use of MSA by the guest.
3557 Once this is done the KVM_REG_MIPS_VEC_* and KVM_REG_MIPS_MSA_* registers can be
3558 accessed, and the Config5.MSAEn bit is accessible via the KVM API and also from
3561 7. Capabilities that can be enabled on VMs
3562 ------------------------------------------
3564 There are certain capabilities that change the behavior of the virtual
3565 machine when enabled. To enable them, please see section 4.37. Below
3566 you can find a list of capabilities and what their effect on the VM
3567 is when enabling them.
3569 The following information is provided along with the description:
3571 Architectures: which instruction set architectures provide this ioctl.
3572 x86 includes both i386 and x86_64.
3574 Parameters: what parameters are accepted by the capability.
3576 Returns: the return value. General error numbers (EBADF, ENOMEM, EINVAL)
3577 are not detailed, but errors with specific meanings are.
3580 7.1 KVM_CAP_PPC_ENABLE_HCALL
3583 Parameters: args[0] is the sPAPR hcall number
3584 args[1] is 0 to disable, 1 to enable in-kernel handling
3586 This capability controls whether individual sPAPR hypercalls (hcalls)
3587 get handled by the kernel or not. Enabling or disabling in-kernel
3588 handling of an hcall is effective across the VM. On creation, an
3589 initial set of hcalls are enabled for in-kernel handling, which
3590 consists of those hcalls for which in-kernel handlers were implemented
3591 before this capability was implemented. If disabled, the kernel will
3592 not to attempt to handle the hcall, but will always exit to userspace
3593 to handle it. Note that it may not make sense to enable some and
3594 disable others of a group of related hcalls, but KVM does not prevent
3595 userspace from doing that.
3597 If the hcall number specified is not one that has an in-kernel
3598 implementation, the KVM_ENABLE_CAP ioctl will fail with an EINVAL
3601 7.2 KVM_CAP_S390_USER_SIGP
3606 This capability controls which SIGP orders will be handled completely in user
3607 space. With this capability enabled, all fast orders will be handled completely
3613 - CONDITIONAL EMERGENCY SIGNAL
3615 All other orders will be handled completely in user space.
3617 Only privileged operation exceptions will be checked for in the kernel (or even
3618 in the hardware prior to interception). If this capability is not enabled, the
3619 old way of handling SIGP orders is used (partially in kernel and user space).
3621 7.3 KVM_CAP_S390_VECTOR_REGISTERS
3625 Returns: 0 on success, negative value on error
3627 Allows use of the vector registers introduced with z13 processor, and
3628 provides for the synchronization between host and user space. Will
3629 return -EINVAL if the machine does not support vectors.
3631 7.4 KVM_CAP_S390_USER_STSI
3636 This capability allows post-handlers for the STSI instruction. After
3637 initial handling in the kernel, KVM exits to user space with
3638 KVM_EXIT_S390_STSI to allow user space to insert further data.
3640 Before exiting to userspace, kvm handlers should fill in s390_stsi field of
3651 @addr - guest address of STSI SYSIB
3655 @ar - access register number
3657 KVM handlers should exit to userspace with rc = -EREMOTE.
3659 7.5 KVM_CAP_SPLIT_IRQCHIP
3662 Parameters: args[0] - number of routes reserved for userspace IOAPICs
3663 Returns: 0 on success, -1 on error
3665 Create a local apic for each processor in the kernel. This can be used
3666 instead of KVM_CREATE_IRQCHIP if the userspace VMM wishes to emulate the
3667 IOAPIC and PIC (and also the PIT, even though this has to be enabled
3670 This capability also enables in kernel routing of interrupt requests;
3671 when KVM_CAP_SPLIT_IRQCHIP only routes of KVM_IRQ_ROUTING_MSI type are
3672 used in the IRQ routing table. The first args[0] MSI routes are reserved
3673 for the IOAPIC pins. Whenever the LAPIC receives an EOI for these routes,
3674 a KVM_EXIT_IOAPIC_EOI vmexit will be reported to userspace.
3676 Fails if VCPU has already been created, or if the irqchip is already in the
3677 kernel (i.e. KVM_CREATE_IRQCHIP has already been called).
3680 8. Other capabilities.
3681 ----------------------
3683 This section lists capabilities that give information about other
3684 features of the KVM implementation.
3686 8.1 KVM_CAP_PPC_HWRNG
3690 This capability, if KVM_CHECK_EXTENSION indicates that it is
3691 available, means that that the kernel has an implementation of the
3692 H_RANDOM hypercall backed by a hardware random-number generator.
3693 If present, the kernel H_RANDOM handler can be enabled for guest use
3694 with the KVM_CAP_PPC_ENABLE_HCALL capability.