kernel/drivers/xen/events/events_2l.c

   1 /*
   2  * Xen event channels (2-level ABI)
   3  *
   4  * Jeremy Fitzhardinge <jeremy@xensource.com>, XenSource Inc, 2007
   5  */
   6
   7 #define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt
   8
   9 #include <linux/linkage.h>
  10 #include <linux/interrupt.h>
  11 #include <linux/irq.h>
  12 #include <linux/module.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 static DEFINE_PER_CPU(xen_ulong_t [EVTCHN_2L_NR_CHANNELS/BITS_PER_EVTCHN_WORD],
  42                       cpu_evtchn_mask);
  43
  44 static unsigned evtchn_2l_max_channels(void)
  45 {
  46         return EVTCHN_2L_NR_CHANNELS;
  47 }
  48
  49 static void evtchn_2l_bind_to_cpu(struct irq_info *info, unsigned cpu)
  50 {
  51         clear_bit(info->evtchn, BM(per_cpu(cpu_evtchn_mask, info->cpu)));
  52         set_bit(info->evtchn, BM(per_cpu(cpu_evtchn_mask, cpu)));
  53 }
  54
  55 static void evtchn_2l_clear_pending(unsigned port)
  56 {
  57         struct shared_info *s = HYPERVISOR_shared_info;
  58         sync_clear_bit(port, BM(&s->evtchn_pending[0]));
  59 }
  60
  61 static void evtchn_2l_set_pending(unsigned port)
  62 {
  63         struct shared_info *s = HYPERVISOR_shared_info;
  64         sync_set_bit(port, BM(&s->evtchn_pending[0]));
  65 }
  66
  67 static bool evtchn_2l_is_pending(unsigned port)
  68 {
  69         struct shared_info *s = HYPERVISOR_shared_info;
  70         return sync_test_bit(port, BM(&s->evtchn_pending[0]));
  71 }
  72
  73 static bool evtchn_2l_test_and_set_mask(unsigned port)
  74 {
  75         struct shared_info *s = HYPERVISOR_shared_info;
  76         return sync_test_and_set_bit(port, BM(&s->evtchn_mask[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         if (unlikely((cpu != cpu_from_evtchn(port))))
  94                 do_hypercall = 1;
  95         else {
  96                 /*
  97                  * Need to clear the mask before checking pending to
  98                  * avoid a race with an event becoming pending.
  99                  *
 100                  * EVTCHNOP_unmask will only trigger an upcall if the
 101                  * mask bit was set, so if a hypercall is needed
 102                  * remask the event.
 103                  */
 104                 sync_clear_bit(port, BM(&s->evtchn_mask[0]));
 105                 evtchn_pending = sync_test_bit(port, BM(&s->evtchn_pending[0]));
 106
 107                 if (unlikely(evtchn_pending && xen_hvm_domain())) {
 108                         sync_set_bit(port, BM(&s->evtchn_mask[0]));
 109                         do_hypercall = 1;
 110                 }
 111         }
 112
 113         /* Slow path (hypercall) if this is a non-local port or if this is
 114          * an hvm domain and an event is pending (hvm domains don't have
 115          * their own implementation of irq_enable). */
 116         if (do_hypercall) {
 117                 struct evtchn_unmask unmask = { .port = port };
 118                 (void)HYPERVISOR_event_channel_op(EVTCHNOP_unmask, &unmask);
 119         } else {
 120                 struct vcpu_info *vcpu_info = __this_cpu_read(xen_vcpu);
 121
 122                 /*
 123                  * The following is basically the equivalent of
 124                  * 'hw_resend_irq'. Just like a real IO-APIC we 'lose
 125                  * the interrupt edge' if the channel is masked.
 126                  */
 127                 if (evtchn_pending &&
 128                     !sync_test_and_set_bit(port / BITS_PER_EVTCHN_WORD,
 129                                            BM(&vcpu_info->evtchn_pending_sel)))
 130                         vcpu_info->evtchn_upcall_pending = 1;
 131         }
 132
 133         put_cpu();
 134 }
 135
 136 static DEFINE_PER_CPU(unsigned int, current_word_idx);
 137 static DEFINE_PER_CPU(unsigned int, current_bit_idx);
 138
 139 /*
 140  * Mask out the i least significant bits of w
 141  */
 142 #define MASK_LSBS(w, i) (w & ((~((xen_ulong_t)0UL)) << i))
 143
 144 static inline xen_ulong_t active_evtchns(unsigned int cpu,
 145                                          struct shared_info *sh,
 146                                          unsigned int idx)
 147 {
 148         return sh->evtchn_pending[idx] &
 149                 per_cpu(cpu_evtchn_mask, cpu)[idx] &
 150                 ~sh->evtchn_mask[idx];
 151 }
 152
 153 /*
 154  * Search the CPU's pending events bitmasks.  For each one found, map
 155  * the event number to an irq, and feed it into do_IRQ() for handling.
 156  *
 157  * Xen uses a two-level bitmap to speed searching.  The first level is
 158  * a bitset of words which contain pending event bits.  The second
 159  * level is a bitset of pending events themselves.
 160  */
 161 static void evtchn_2l_handle_events(unsigned cpu)
 162 {
 163         int irq;
 164         xen_ulong_t pending_words;
 165         xen_ulong_t pending_bits;
 166         int start_word_idx, start_bit_idx;
 167         int word_idx, bit_idx;
 168         int i;
 169         struct shared_info *s = HYPERVISOR_shared_info;
 170         struct vcpu_info *vcpu_info = __this_cpu_read(xen_vcpu);
 171
 172         /* Timer interrupt has highest priority. */
 173         irq = irq_from_virq(cpu, VIRQ_TIMER);
 174         if (irq != -1) {
 175                 unsigned int evtchn = evtchn_from_irq(irq);
 176                 word_idx = evtchn / BITS_PER_LONG;
 177                 bit_idx = evtchn % BITS_PER_LONG;
 178                 if (active_evtchns(cpu, s, word_idx) & (1ULL << bit_idx))
 179                         generic_handle_irq(irq);
 180         }
 181
 182         /*
 183          * Master flag must be cleared /before/ clearing
 184          * selector flag. xchg_xen_ulong must contain an
 185          * appropriate barrier.
 186          */
 187         pending_words = xchg_xen_ulong(&vcpu_info->evtchn_pending_sel, 0);
 188
 189         start_word_idx = __this_cpu_read(current_word_idx);
 190         start_bit_idx = __this_cpu_read(current_bit_idx);
 191
 192         word_idx = start_word_idx;
 193
 194         for (i = 0; pending_words != 0; i++) {
 195                 xen_ulong_t words;
 196
 197                 words = MASK_LSBS(pending_words, word_idx);
 198
 199                 /*
 200                  * If we masked out all events, wrap to beginning.
 201                  */
 202                 if (words == 0) {
 203                         word_idx = 0;
 204                         bit_idx = 0;
 205                         continue;
 206                 }
 207                 word_idx = EVTCHN_FIRST_BIT(words);
 208
 209                 pending_bits = active_evtchns(cpu, s, word_idx);
 210                 bit_idx = 0; /* usually scan entire word from start */
 211                 /*
 212                  * We scan the starting word in two parts.
 213                  *
 214                  * 1st time: start in the middle, scanning the
 215                  * upper bits.
 216                  *
 217                  * 2nd time: scan the whole word (not just the
 218                  * parts skipped in the first pass) -- if an
 219                  * event in the previously scanned bits is
 220                  * pending again it would just be scanned on
 221                  * the next loop anyway.
 222                  */
 223                 if (word_idx == start_word_idx) {
 224                         if (i == 0)
 225                                 bit_idx = start_bit_idx;
 226                 }
 227
 228                 do {
 229                         xen_ulong_t bits;
 230                         int port;
 231
 232                         bits = MASK_LSBS(pending_bits, bit_idx);
 233
 234                         /* If we masked out all events, move on. */
 235                         if (bits == 0)
 236                                 break;
 237
 238                         bit_idx = EVTCHN_FIRST_BIT(bits);
 239
 240                         /* Process port. */
 241                         port = (word_idx * BITS_PER_EVTCHN_WORD) + bit_idx;
 242                         irq = get_evtchn_to_irq(port);
 243
 244                         if (irq != -1)
 245                                 generic_handle_irq(irq);
 246
 247                         bit_idx = (bit_idx + 1) % BITS_PER_EVTCHN_WORD;
 248
 249                         /* Next caller starts at last processed + 1 */
 250                         __this_cpu_write(current_word_idx,
 251                                          bit_idx ? word_idx :
 252                                          (word_idx+1) % BITS_PER_EVTCHN_WORD);
 253                         __this_cpu_write(current_bit_idx, bit_idx);
 254                 } while (bit_idx != 0);
 255
 256                 /* Scan start_l1i twice; all others once. */
 257                 if ((word_idx != start_word_idx) || (i != 0))
 258                         pending_words &= ~(1UL << word_idx);
 259
 260                 word_idx = (word_idx + 1) % BITS_PER_EVTCHN_WORD;
 261         }
 262 }
 263
 264 irqreturn_t xen_debug_interrupt(int irq, void *dev_id)
 265 {
 266         struct shared_info *sh = HYPERVISOR_shared_info;
 267         int cpu = smp_processor_id();
 268         xen_ulong_t *cpu_evtchn = per_cpu(cpu_evtchn_mask, cpu);
 269         int i;
 270         unsigned long flags;
 271         static DEFINE_SPINLOCK(debug_lock);
 272         struct vcpu_info *v;
 273
 274         spin_lock_irqsave(&debug_lock, flags);
 275
 276         printk("\nvcpu %d\n  ", cpu);
 277
 278         for_each_online_cpu(i) {
 279                 int pending;
 280                 v = per_cpu(xen_vcpu, i);
 281                 pending = (get_irq_regs() && i == cpu)
 282                         ? xen_irqs_disabled(get_irq_regs())
 283                         : v->evtchn_upcall_mask;
 284                 printk("%d: masked=%d pending=%d event_sel %0*"PRI_xen_ulong"\n  ", i,
 285                        pending, v->evtchn_upcall_pending,
 286                        (int)(sizeof(v->evtchn_pending_sel)*2),
 287                        v->evtchn_pending_sel);
 288         }
 289         v = per_cpu(xen_vcpu, cpu);
 290
 291         printk("\npending:\n   ");
 292         for (i = ARRAY_SIZE(sh->evtchn_pending)-1; i >= 0; i--)
 293                 printk("%0*"PRI_xen_ulong"%s",
 294                        (int)sizeof(sh->evtchn_pending[0])*2,
 295                        sh->evtchn_pending[i],
 296                        i % 8 == 0 ? "\n   " : " ");
 297         printk("\nglobal mask:\n   ");
 298         for (i = ARRAY_SIZE(sh->evtchn_mask)-1; i >= 0; i--)
 299                 printk("%0*"PRI_xen_ulong"%s",
 300                        (int)(sizeof(sh->evtchn_mask[0])*2),
 301                        sh->evtchn_mask[i],
 302                        i % 8 == 0 ? "\n   " : " ");
 303
 304         printk("\nglobally unmasked:\n   ");
 305         for (i = ARRAY_SIZE(sh->evtchn_mask)-1; i >= 0; i--)
 306                 printk("%0*"PRI_xen_ulong"%s",
 307                        (int)(sizeof(sh->evtchn_mask[0])*2),
 308                        sh->evtchn_pending[i] & ~sh->evtchn_mask[i],
 309                        i % 8 == 0 ? "\n   " : " ");
 310
 311         printk("\nlocal cpu%d mask:\n   ", cpu);
 312         for (i = (EVTCHN_2L_NR_CHANNELS/BITS_PER_EVTCHN_WORD)-1; i >= 0; i--)
 313                 printk("%0*"PRI_xen_ulong"%s", (int)(sizeof(cpu_evtchn[0])*2),
 314                        cpu_evtchn[i],
 315                        i % 8 == 0 ? "\n   " : " ");
 316
 317         printk("\nlocally unmasked:\n   ");
 318         for (i = ARRAY_SIZE(sh->evtchn_mask)-1; i >= 0; i--) {
 319                 xen_ulong_t pending = sh->evtchn_pending[i]
 320                         & ~sh->evtchn_mask[i]
 321                         & cpu_evtchn[i];
 322                 printk("%0*"PRI_xen_ulong"%s",
 323                        (int)(sizeof(sh->evtchn_mask[0])*2),
 324                        pending, i % 8 == 0 ? "\n   " : " ");
 325         }
 326
 327         printk("\npending list:\n");
 328         for (i = 0; i < EVTCHN_2L_NR_CHANNELS; i++) {
 329                 if (sync_test_bit(i, BM(sh->evtchn_pending))) {
 330                         int word_idx = i / BITS_PER_EVTCHN_WORD;
 331                         printk("  %d: event %d -> irq %d%s%s%s\n",
 332                                cpu_from_evtchn(i), i,
 333                                get_evtchn_to_irq(i),
 334                                sync_test_bit(word_idx, BM(&v->evtchn_pending_sel))
 335                                ? "" : " l2-clear",
 336                                !sync_test_bit(i, BM(sh->evtchn_mask))
 337                                ? "" : " globally-masked",
 338                                sync_test_bit(i, BM(cpu_evtchn))
 339                                ? "" : " locally-masked");
 340                 }
 341         }
 342
 343         spin_unlock_irqrestore(&debug_lock, flags);
 344
 345         return IRQ_HANDLED;
 346 }
 347
 348 static void evtchn_2l_resume(void)
 349 {
 350         int i;
 351
 352         for_each_online_cpu(i)
 353                 memset(per_cpu(cpu_evtchn_mask, i), 0, sizeof(xen_ulong_t) *
 354                                 EVTCHN_2L_NR_CHANNELS/BITS_PER_EVTCHN_WORD);
 355 }
 356
 357 static const struct evtchn_ops evtchn_ops_2l = {
 358         .max_channels      = evtchn_2l_max_channels,
 359         .nr_channels       = evtchn_2l_max_channels,
 360         .bind_to_cpu       = evtchn_2l_bind_to_cpu,
 361         .clear_pending     = evtchn_2l_clear_pending,
 362         .set_pending       = evtchn_2l_set_pending,
 363         .is_pending        = evtchn_2l_is_pending,
 364         .test_and_set_mask = evtchn_2l_test_and_set_mask,
 365         .mask              = evtchn_2l_mask,
 366         .unmask            = evtchn_2l_unmask,
 367         .handle_events     = evtchn_2l_handle_events,
 368         .resume            = evtchn_2l_resume,
 369 };
 370
 371 void __init xen_evtchn_2l_init(void)
 372 {
 373         pr_info("Using 2-level ABI\n");
 374         evtchn_ops = &evtchn_ops_2l;
 375 }