drivers/xen/events/events_2l.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Xen event channels (2-level ABI)
   4  *
   5  * Jeremy Fitzhardinge <jeremy@xensource.com>, XenSource Inc, 2007
   6  */
   7
   8 #define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt
   9
  10 #include <linux/linkage.h>
  11 #include <linux/interrupt.h>
  12 #include <linux/irq.h>
  13
  14 #include <asm/sync_bitops.h>
  15 #include <asm/xen/hypercall.h>
  16 #include <asm/xen/hypervisor.h>
  17
  18 #include <xen/xen.h>
  19 #include <xen/xen-ops.h>
  20 #include <xen/events.h>
  21 #include <xen/interface/xen.h>
  22 #include <xen/interface/event_channel.h>
  23
  24 #include "events_internal.h"
  25
  26 /*
  27  * Note sizeof(xen_ulong_t) can be more than sizeof(unsigned long). Be
  28  * careful to only use bitops which allow for this (e.g
  29  * test_bit/find_first_bit and friends but not __ffs) and to pass
  30  * BITS_PER_EVTCHN_WORD as the bitmask length.
  31  */
  32 #define BITS_PER_EVTCHN_WORD (sizeof(xen_ulong_t)*8)
  33 /*
  34  * Make a bitmask (i.e. unsigned long *) of a xen_ulong_t
  35  * array. Primarily to avoid long lines (hence the terse name).
  36  */
  37 #define BM(x) (unsigned long *)(x)
  38 /* Find the first set bit in a evtchn mask */
  39 #define EVTCHN_FIRST_BIT(w) find_first_bit(BM(&(w)), BITS_PER_EVTCHN_WORD)
  40
  41 #define EVTCHN_MASK_SIZE (EVTCHN_2L_NR_CHANNELS/BITS_PER_EVTCHN_WORD)
  42
  43 static DEFINE_PER_CPU(xen_ulong_t [EVTCHN_MASK_SIZE], cpu_evtchn_mask);
  44
  45 static unsigned evtchn_2l_max_channels(void)
  46 {
  47         return EVTCHN_2L_NR_CHANNELS;
  48 }
  49
  50 static void evtchn_2l_remove(evtchn_port_t evtchn, unsigned int cpu)
  51 {
  52         clear_bit(evtchn, BM(per_cpu(cpu_evtchn_mask, cpu)));
  53 }
  54
  55 static void evtchn_2l_bind_to_cpu(struct irq_info *info, unsigned cpu)
  56 {
  57         clear_bit(info->evtchn, BM(per_cpu(cpu_evtchn_mask, info->cpu)));
  58         set_bit(info->evtchn, BM(per_cpu(cpu_evtchn_mask, cpu)));
  59 }
  60
  61 static void evtchn_2l_clear_pending(unsigned port)
  62 {
  63         struct shared_info *s = HYPERVISOR_shared_info;
  64         sync_clear_bit(port, BM(&s->evtchn_pending[0]));
  65 }
  66
  67 static void evtchn_2l_set_pending(unsigned port)
  68 {
  69         struct shared_info *s = HYPERVISOR_shared_info;
  70         sync_set_bit(port, BM(&s->evtchn_pending[0]));
  71 }
  72
  73 static bool evtchn_2l_is_pending(unsigned port)
  74 {
  75         struct shared_info *s = HYPERVISOR_shared_info;
  76         return sync_test_bit(port, BM(&s->evtchn_pending[0]));
  77 }
  78
  79 static void evtchn_2l_mask(unsigned port)
  80 {
  81         struct shared_info *s = HYPERVISOR_shared_info;
  82         sync_set_bit(port, BM(&s->evtchn_mask[0]));
  83 }
  84
  85 static void evtchn_2l_unmask(unsigned port)
  86 {
  87         struct shared_info *s = HYPERVISOR_shared_info;
  88         unsigned int cpu = get_cpu();
  89         int do_hypercall = 0, evtchn_pending = 0;
  90
  91         BUG_ON(!irqs_disabled());
  92
  93         smp_wmb();      /* All writes before unmask must be visible. */
  94
  95         if (unlikely((cpu != cpu_from_evtchn(port))))
  96                 do_hypercall = 1;
  97         else {
  98                 /*
  99                  * Need to clear the mask before checking pending to
 100                  * avoid a race with an event becoming pending.
 101                  *
 102                  * EVTCHNOP_unmask will only trigger an upcall if the
 103                  * mask bit was set, so if a hypercall is needed
 104                  * remask the event.
 105                  */
 106                 sync_clear_bit(port, BM(&s->evtchn_mask[0]));
 107                 evtchn_pending = sync_test_bit(port, BM(&s->evtchn_pending[0]));
 108
 109                 if (unlikely(evtchn_pending && xen_hvm_domain())) {
 110                         sync_set_bit(port, BM(&s->evtchn_mask[0]));
 111                         do_hypercall = 1;
 112                 }
 113         }
 114
 115         /* Slow path (hypercall) if this is a non-local port or if this is
 116          * an hvm domain and an event is pending (hvm domains don't have
 117          * their own implementation of irq_enable). */
 118         if (do_hypercall) {
 119                 struct evtchn_unmask unmask = { .port = port };
 120                 (void)HYPERVISOR_event_channel_op(EVTCHNOP_unmask, &unmask);
 121         } else {
 122                 struct vcpu_info *vcpu_info = __this_cpu_read(xen_vcpu);
 123
 124                 /*
 125                  * The following is basically the equivalent of
 126                  * 'hw_resend_irq'. Just like a real IO-APIC we 'lose
 127                  * the interrupt edge' if the channel is masked.
 128                  */
 129                 if (evtchn_pending &&
 130                     !sync_test_and_set_bit(port / BITS_PER_EVTCHN_WORD,
 131                                            BM(&vcpu_info->evtchn_pending_sel)))
 132                         vcpu_info->evtchn_upcall_pending = 1;
 133         }
 134
 135         put_cpu();
 136 }
 137
 138 static DEFINE_PER_CPU(unsigned int, current_word_idx);
 139 static DEFINE_PER_CPU(unsigned int, current_bit_idx);
 140
 141 /*
 142  * Mask out the i least significant bits of w
 143  */
 144 #define MASK_LSBS(w, i) (w & ((~((xen_ulong_t)0UL)) << i))
 145
 146 static inline xen_ulong_t active_evtchns(unsigned int cpu,
 147                                          struct shared_info *sh,
 148                                          unsigned int idx)
 149 {
 150         return sh->evtchn_pending[idx] &
 151                 per_cpu(cpu_evtchn_mask, cpu)[idx] &
 152                 ~sh->evtchn_mask[idx];
 153 }
 154
 155 /*
 156  * Search the CPU's pending events bitmasks.  For each one found, map
 157  * the event number to an irq, and feed it into do_IRQ() for handling.
 158  *
 159  * Xen uses a two-level bitmap to speed searching.  The first level is
 160  * a bitset of words which contain pending event bits.  The second
 161  * level is a bitset of pending events themselves.
 162  */
 163 static void evtchn_2l_handle_events(unsigned cpu, struct evtchn_loop_ctrl *ctrl)
 164 {
 165         int irq;
 166         xen_ulong_t pending_words;
 167         xen_ulong_t pending_bits;
 168         int start_word_idx, start_bit_idx;
 169         int word_idx, bit_idx;
 170         int i;
 171         struct shared_info *s = HYPERVISOR_shared_info;
 172         struct vcpu_info *vcpu_info = __this_cpu_read(xen_vcpu);
 173
 174         /* Timer interrupt has highest priority. */
 175         irq = irq_from_virq(cpu, VIRQ_TIMER);
 176         if (irq != -1) {
 177                 unsigned int evtchn = evtchn_from_irq(irq);
 178                 word_idx = evtchn / BITS_PER_LONG;
 179                 bit_idx = evtchn % BITS_PER_LONG;
 180                 if (active_evtchns(cpu, s, word_idx) & (1ULL << bit_idx))
 181                         generic_handle_irq(irq);
 182         }
 183
 184         /*
 185          * Master flag must be cleared /before/ clearing
 186          * selector flag. xchg_xen_ulong must contain an
 187          * appropriate barrier.
 188          */
 189         pending_words = xchg_xen_ulong(&vcpu_info->evtchn_pending_sel, 0);
 190
 191         start_word_idx = __this_cpu_read(current_word_idx);
 192         start_bit_idx = __this_cpu_read(current_bit_idx);
 193
 194         word_idx = start_word_idx;
 195
 196         for (i = 0; pending_words != 0; i++) {
 197                 xen_ulong_t words;
 198
 199                 words = MASK_LSBS(pending_words, word_idx);
 200
 201                 /*
 202                  * If we masked out all events, wrap to beginning.
 203                  */
 204                 if (words == 0) {
 205                         word_idx = 0;
 206                         bit_idx = 0;
 207                         continue;
 208                 }
 209                 word_idx = EVTCHN_FIRST_BIT(words);
 210
 211                 pending_bits = active_evtchns(cpu, s, word_idx);
 212                 bit_idx = 0; /* usually scan entire word from start */
 213                 /*
 214                  * We scan the starting word in two parts.
 215                  *
 216                  * 1st time: start in the middle, scanning the
 217                  * upper bits.
 218                  *
 219                  * 2nd time: scan the whole word (not just the
 220                  * parts skipped in the first pass) -- if an
 221                  * event in the previously scanned bits is
 222                  * pending again it would just be scanned on
 223                  * the next loop anyway.
 224                  */
 225                 if (word_idx == start_word_idx) {
 226                         if (i == 0)
 227                                 bit_idx = start_bit_idx;
 228                 }
 229
 230                 do {
 231                         xen_ulong_t bits;
 232                         int port;
 233
 234                         bits = MASK_LSBS(pending_bits, bit_idx);
 235
 236                         /* If we masked out all events, move on. */
 237                         if (bits == 0)
 238                                 break;
 239
 240                         bit_idx = EVTCHN_FIRST_BIT(bits);
 241
 242                         /* Process port. */
 243                         port = (word_idx * BITS_PER_EVTCHN_WORD) + bit_idx;
 244                         handle_irq_for_port(port, ctrl);
 245
 246                         bit_idx = (bit_idx + 1) % BITS_PER_EVTCHN_WORD;
 247
 248                         /* Next caller starts at last processed + 1 */
 249                         __this_cpu_write(current_word_idx,
 250                                          bit_idx ? word_idx :
 251                                          (word_idx+1) % BITS_PER_EVTCHN_WORD);
 252                         __this_cpu_write(current_bit_idx, bit_idx);
 253                 } while (bit_idx != 0);
 254
 255                 /* Scan start_l1i twice; all others once. */
 256                 if ((word_idx != start_word_idx) || (i != 0))
 257                         pending_words &= ~(1UL << word_idx);
 258
 259                 word_idx = (word_idx + 1) % BITS_PER_EVTCHN_WORD;
 260         }
 261 }
 262
 263 irqreturn_t xen_debug_interrupt(int irq, void *dev_id)
 264 {
 265         struct shared_info *sh = HYPERVISOR_shared_info;
 266         int cpu = smp_processor_id();
 267         xen_ulong_t *cpu_evtchn = per_cpu(cpu_evtchn_mask, cpu);
 268         int i;
 269         unsigned long flags;
 270         static DEFINE_SPINLOCK(debug_lock);
 271         struct vcpu_info *v;
 272
 273         spin_lock_irqsave(&debug_lock, flags);
 274
 275         printk("\nvcpu %d\n  ", cpu);
 276
 277         for_each_online_cpu(i) {
 278                 int pending;
 279                 v = per_cpu(xen_vcpu, i);
 280                 pending = (get_irq_regs() && i == cpu)
 281                         ? xen_irqs_disabled(get_irq_regs())
 282                         : v->evtchn_upcall_mask;
 283                 printk("%d: masked=%d pending=%d event_sel %0*"PRI_xen_ulong"\n  ", i,
 284                        pending, v->evtchn_upcall_pending,
 285                        (int)(sizeof(v->evtchn_pending_sel)*2),
 286                        v->evtchn_pending_sel);
 287         }
 288         v = per_cpu(xen_vcpu, cpu);
 289
 290         printk("\npending:\n   ");
 291         for (i = ARRAY_SIZE(sh->evtchn_pending)-1; i >= 0; i--)
 292                 printk("%0*"PRI_xen_ulong"%s",
 293                        (int)sizeof(sh->evtchn_pending[0])*2,
 294                        sh->evtchn_pending[i],
 295                        i % 8 == 0 ? "\n   " : " ");
 296         printk("\nglobal mask:\n   ");
 297         for (i = ARRAY_SIZE(sh->evtchn_mask)-1; i >= 0; i--)
 298                 printk("%0*"PRI_xen_ulong"%s",
 299                        (int)(sizeof(sh->evtchn_mask[0])*2),
 300                        sh->evtchn_mask[i],
 301                        i % 8 == 0 ? "\n   " : " ");
 302
 303         printk("\nglobally unmasked:\n   ");
 304         for (i = ARRAY_SIZE(sh->evtchn_mask)-1; i >= 0; i--)
 305                 printk("%0*"PRI_xen_ulong"%s",
 306                        (int)(sizeof(sh->evtchn_mask[0])*2),
 307                        sh->evtchn_pending[i] & ~sh->evtchn_mask[i],
 308                        i % 8 == 0 ? "\n   " : " ");
 309
 310         printk("\nlocal cpu%d mask:\n   ", cpu);
 311         for (i = (EVTCHN_2L_NR_CHANNELS/BITS_PER_EVTCHN_WORD)-1; i >= 0; i--)
 312                 printk("%0*"PRI_xen_ulong"%s", (int)(sizeof(cpu_evtchn[0])*2),
 313                        cpu_evtchn[i],
 314                        i % 8 == 0 ? "\n   " : " ");
 315
 316         printk("\nlocally unmasked:\n   ");
 317         for (i = ARRAY_SIZE(sh->evtchn_mask)-1; i >= 0; i--) {
 318                 xen_ulong_t pending = sh->evtchn_pending[i]
 319                         & ~sh->evtchn_mask[i]
 320                         & cpu_evtchn[i];
 321                 printk("%0*"PRI_xen_ulong"%s",
 322                        (int)(sizeof(sh->evtchn_mask[0])*2),
 323                        pending, i % 8 == 0 ? "\n   " : " ");
 324         }
 325
 326         printk("\npending list:\n");
 327         for (i = 0; i < EVTCHN_2L_NR_CHANNELS; i++) {
 328                 if (sync_test_bit(i, BM(sh->evtchn_pending))) {
 329                         int word_idx = i / BITS_PER_EVTCHN_WORD;
 330                         printk("  %d: event %d -> irq %d%s%s%s\n",
 331                                cpu_from_evtchn(i), i,
 332                                get_evtchn_to_irq(i),
 333                                sync_test_bit(word_idx, BM(&v->evtchn_pending_sel))
 334                                ? "" : " l2-clear",
 335                                !sync_test_bit(i, BM(sh->evtchn_mask))
 336                                ? "" : " globally-masked",
 337                                sync_test_bit(i, BM(cpu_evtchn))
 338                                ? "" : " locally-masked");
 339                 }
 340         }
 341
 342         spin_unlock_irqrestore(&debug_lock, flags);
 343
 344         return IRQ_HANDLED;
 345 }
 346
 347 static void evtchn_2l_resume(void)
 348 {
 349         int i;
 350
 351         for_each_online_cpu(i)
 352                 memset(per_cpu(cpu_evtchn_mask, i), 0, sizeof(xen_ulong_t) *
 353                                 EVTCHN_2L_NR_CHANNELS/BITS_PER_EVTCHN_WORD);
 354 }
 355
 356 static int evtchn_2l_percpu_deinit(unsigned int cpu)
 357 {
 358         memset(per_cpu(cpu_evtchn_mask, cpu), 0, sizeof(xen_ulong_t) *
 359                         EVTCHN_2L_NR_CHANNELS/BITS_PER_EVTCHN_WORD);
 360
 361         return 0;
 362 }
 363
 364 static const struct evtchn_ops evtchn_ops_2l = {
 365         .max_channels      = evtchn_2l_max_channels,
 366         .nr_channels       = evtchn_2l_max_channels,
 367         .remove            = evtchn_2l_remove,
 368         .bind_to_cpu       = evtchn_2l_bind_to_cpu,
 369         .clear_pending     = evtchn_2l_clear_pending,
 370         .set_pending       = evtchn_2l_set_pending,
 371         .is_pending        = evtchn_2l_is_pending,
 372         .mask              = evtchn_2l_mask,
 373         .unmask            = evtchn_2l_unmask,
 374         .handle_events     = evtchn_2l_handle_events,
 375         .resume            = evtchn_2l_resume,
 376         .percpu_deinit     = evtchn_2l_percpu_deinit,
 377 };
 378
 379 void __init xen_evtchn_2l_init(void)
 380 {
 381         pr_info("Using 2-level ABI\n");
 382         evtchn_ops = &evtchn_ops_2l;
 383 }