Pileus Git - ~andy/linux/blob - 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 [NR_EVENT_CHANNELS/BITS_PER_EVTCHN_WORD],
  42                       cpu_evtchn_mask);
  43
  44 void xen_evtchn_port_bind_to_cpu(struct irq_info *info, int cpu)
  45 {
  46         clear_bit(info->evtchn, BM(per_cpu(cpu_evtchn_mask, info->cpu)));
  47         set_bit(info->evtchn, BM(per_cpu(cpu_evtchn_mask, cpu)));
  48 }
  49
  50 void clear_evtchn(int port)
  51 {
  52         struct shared_info *s = HYPERVISOR_shared_info;
  53         sync_clear_bit(port, BM(&s->evtchn_pending[0]));
  54 }
  55
  56 void set_evtchn(int port)
  57 {
  58         struct shared_info *s = HYPERVISOR_shared_info;
  59         sync_set_bit(port, BM(&s->evtchn_pending[0]));
  60 }
  61
  62 int test_evtchn(int port)
  63 {
  64         struct shared_info *s = HYPERVISOR_shared_info;
  65         return sync_test_bit(port, BM(&s->evtchn_pending[0]));
  66 }
  67
  68 int test_and_set_mask(int port)
  69 {
  70         struct shared_info *s = HYPERVISOR_shared_info;
  71         return sync_test_and_set_bit(port, BM(&s->evtchn_mask[0]));
  72 }
  73
  74 void mask_evtchn(int port)
  75 {
  76         struct shared_info *s = HYPERVISOR_shared_info;
  77         sync_set_bit(port, BM(&s->evtchn_mask[0]));
  78 }
  79
  80 void unmask_evtchn(int port)
  81 {
  82         struct shared_info *s = HYPERVISOR_shared_info;
  83         unsigned int cpu = get_cpu();
  84         int do_hypercall = 0, evtchn_pending = 0;
  85
  86         BUG_ON(!irqs_disabled());
  87
  88         if (unlikely((cpu != cpu_from_evtchn(port))))
  89                 do_hypercall = 1;
  90         else {
  91                 /*
  92                  * Need to clear the mask before checking pending to
  93                  * avoid a race with an event becoming pending.
  94                  *
  95                  * EVTCHNOP_unmask will only trigger an upcall if the
  96                  * mask bit was set, so if a hypercall is needed
  97                  * remask the event.
  98                  */
  99                 sync_clear_bit(port, BM(&s->evtchn_mask[0]));
 100                 evtchn_pending = sync_test_bit(port, BM(&s->evtchn_pending[0]));
 101
 102                 if (unlikely(evtchn_pending && xen_hvm_domain())) {
 103                         sync_set_bit(port, BM(&s->evtchn_mask[0]));
 104                         do_hypercall = 1;
 105                 }
 106         }
 107
 108         /* Slow path (hypercall) if this is a non-local port or if this is
 109          * an hvm domain and an event is pending (hvm domains don't have
 110          * their own implementation of irq_enable). */
 111         if (do_hypercall) {
 112                 struct evtchn_unmask unmask = { .port = port };
 113                 (void)HYPERVISOR_event_channel_op(EVTCHNOP_unmask, &unmask);
 114         } else {
 115                 struct vcpu_info *vcpu_info = __this_cpu_read(xen_vcpu);
 116
 117                 /*
 118                  * The following is basically the equivalent of
 119                  * 'hw_resend_irq'. Just like a real IO-APIC we 'lose
 120                  * the interrupt edge' if the channel is masked.
 121                  */
 122                 if (evtchn_pending &&
 123                     !sync_test_and_set_bit(port / BITS_PER_EVTCHN_WORD,
 124                                            BM(&vcpu_info->evtchn_pending_sel)))
 125                         vcpu_info->evtchn_upcall_pending = 1;
 126         }
 127
 128         put_cpu();
 129 }
 130
 131 static DEFINE_PER_CPU(unsigned int, current_word_idx);
 132 static DEFINE_PER_CPU(unsigned int, current_bit_idx);
 133
 134 /*
 135  * Mask out the i least significant bits of w
 136  */
 137 #define MASK_LSBS(w, i) (w & ((~((xen_ulong_t)0UL)) << i))
 138
 139 static inline xen_ulong_t active_evtchns(unsigned int cpu,
 140                                          struct shared_info *sh,
 141                                          unsigned int idx)
 142 {
 143         return sh->evtchn_pending[idx] &
 144                 per_cpu(cpu_evtchn_mask, cpu)[idx] &
 145                 ~sh->evtchn_mask[idx];
 146 }
 147
 148 /*
 149  * Search the CPU's pending events bitmasks.  For each one found, map
 150  * the event number to an irq, and feed it into do_IRQ() for handling.
 151  *
 152  * Xen uses a two-level bitmap to speed searching.  The first level is
 153  * a bitset of words which contain pending event bits.  The second
 154  * level is a bitset of pending events themselves.
 155  */
 156 void xen_evtchn_handle_events(int cpu)
 157 {
 158         int irq;
 159         xen_ulong_t pending_words;
 160         xen_ulong_t pending_bits;
 161         int start_word_idx, start_bit_idx;
 162         int word_idx, bit_idx;
 163         int i;
 164         struct irq_desc *desc;
 165         struct shared_info *s = HYPERVISOR_shared_info;
 166         struct vcpu_info *vcpu_info = __this_cpu_read(xen_vcpu);
 167
 168         /* Timer interrupt has highest priority. */
 169         irq = irq_from_virq(cpu, VIRQ_TIMER);
 170         if (irq != -1) {
 171                 unsigned int evtchn = evtchn_from_irq(irq);
 172                 word_idx = evtchn / BITS_PER_LONG;
 173                 bit_idx = evtchn % BITS_PER_LONG;
 174                 if (active_evtchns(cpu, s, word_idx) & (1ULL << bit_idx)) {
 175                         desc = irq_to_desc(irq);
 176                         if (desc)
 177                                 generic_handle_irq_desc(irq, desc);
 178                 }
 179         }
 180
 181         /*
 182          * Master flag must be cleared /before/ clearing
 183          * selector flag. xchg_xen_ulong must contain an
 184          * appropriate barrier.
 185          */
 186         pending_words = xchg_xen_ulong(&vcpu_info->evtchn_pending_sel, 0);
 187
 188         start_word_idx = __this_cpu_read(current_word_idx);
 189         start_bit_idx = __this_cpu_read(current_bit_idx);
 190
 191         word_idx = start_word_idx;
 192
 193         for (i = 0; pending_words != 0; i++) {
 194                 xen_ulong_t words;
 195
 196                 words = MASK_LSBS(pending_words, word_idx);
 197
 198                 /*
 199                  * If we masked out all events, wrap to beginning.
 200                  */
 201                 if (words == 0) {
 202                         word_idx = 0;
 203                         bit_idx = 0;
 204                         continue;
 205                 }
 206                 word_idx = EVTCHN_FIRST_BIT(words);
 207
 208                 pending_bits = active_evtchns(cpu, s, word_idx);
 209                 bit_idx = 0; /* usually scan entire word from start */
 210                 /*
 211                  * We scan the starting word in two parts.
 212                  *
 213                  * 1st time: start in the middle, scanning the
 214                  * upper bits.
 215                  *
 216                  * 2nd time: scan the whole word (not just the
 217                  * parts skipped in the first pass) -- if an
 218                  * event in the previously scanned bits is
 219                  * pending again it would just be scanned on
 220                  * the next loop anyway.
 221                  */
 222                 if (word_idx == start_word_idx) {
 223                         if (i == 0)
 224                                 bit_idx = start_bit_idx;
 225                 }
 226
 227                 do {
 228                         xen_ulong_t bits;
 229                         int port;
 230
 231                         bits = MASK_LSBS(pending_bits, bit_idx);
 232
 233                         /* If we masked out all events, move on. */
 234                         if (bits == 0)
 235                                 break;
 236
 237                         bit_idx = EVTCHN_FIRST_BIT(bits);
 238
 239                         /* Process port. */
 240                         port = (word_idx * BITS_PER_EVTCHN_WORD) + bit_idx;
 241                         irq = evtchn_to_irq[port];
 242
 243                         if (irq != -1) {
 244                                 desc = irq_to_desc(irq);
 245                                 if (desc)
 246                                         generic_handle_irq_desc(irq, desc);
 247                         }
 248
 249                         bit_idx = (bit_idx + 1) % BITS_PER_EVTCHN_WORD;
 250
 251                         /* Next caller starts at last processed + 1 */
 252                         __this_cpu_write(current_word_idx,
 253                                          bit_idx ? word_idx :
 254                                          (word_idx+1) % BITS_PER_EVTCHN_WORD);
 255                         __this_cpu_write(current_bit_idx, bit_idx);
 256                 } while (bit_idx != 0);
 257
 258                 /* Scan start_l1i twice; all others once. */
 259                 if ((word_idx != start_word_idx) || (i != 0))
 260                         pending_words &= ~(1UL << word_idx);
 261
 262                 word_idx = (word_idx + 1) % BITS_PER_EVTCHN_WORD;
 263         }
 264 }
 265
 266 irqreturn_t xen_debug_interrupt(int irq, void *dev_id)
 267 {
 268         struct shared_info *sh = HYPERVISOR_shared_info;
 269         int cpu = smp_processor_id();
 270         xen_ulong_t *cpu_evtchn = per_cpu(cpu_evtchn_mask, cpu);
 271         int i;
 272         unsigned long flags;
 273         static DEFINE_SPINLOCK(debug_lock);
 274         struct vcpu_info *v;
 275
 276         spin_lock_irqsave(&debug_lock, flags);
 277
 278         printk("\nvcpu %d\n  ", cpu);
 279
 280         for_each_online_cpu(i) {
 281                 int pending;
 282                 v = per_cpu(xen_vcpu, i);
 283                 pending = (get_irq_regs() && i == cpu)
 284                         ? xen_irqs_disabled(get_irq_regs())
 285                         : v->evtchn_upcall_mask;
 286                 printk("%d: masked=%d pending=%d event_sel %0*"PRI_xen_ulong"\n  ", i,
 287                        pending, v->evtchn_upcall_pending,
 288                        (int)(sizeof(v->evtchn_pending_sel)*2),
 289                        v->evtchn_pending_sel);
 290         }
 291         v = per_cpu(xen_vcpu, cpu);
 292
 293         printk("\npending:\n   ");
 294         for (i = ARRAY_SIZE(sh->evtchn_pending)-1; i >= 0; i--)
 295                 printk("%0*"PRI_xen_ulong"%s",
 296                        (int)sizeof(sh->evtchn_pending[0])*2,
 297                        sh->evtchn_pending[i],
 298                        i % 8 == 0 ? "\n   " : " ");
 299         printk("\nglobal mask:\n   ");
 300         for (i = ARRAY_SIZE(sh->evtchn_mask)-1; i >= 0; i--)
 301                 printk("%0*"PRI_xen_ulong"%s",
 302                        (int)(sizeof(sh->evtchn_mask[0])*2),
 303                        sh->evtchn_mask[i],
 304                        i % 8 == 0 ? "\n   " : " ");
 305
 306         printk("\nglobally unmasked:\n   ");
 307         for (i = ARRAY_SIZE(sh->evtchn_mask)-1; i >= 0; i--)
 308                 printk("%0*"PRI_xen_ulong"%s",
 309                        (int)(sizeof(sh->evtchn_mask[0])*2),
 310                        sh->evtchn_pending[i] & ~sh->evtchn_mask[i],
 311                        i % 8 == 0 ? "\n   " : " ");
 312
 313         printk("\nlocal cpu%d mask:\n   ", cpu);
 314         for (i = (NR_EVENT_CHANNELS/BITS_PER_EVTCHN_WORD)-1; i >= 0; i--)
 315                 printk("%0*"PRI_xen_ulong"%s", (int)(sizeof(cpu_evtchn[0])*2),
 316                        cpu_evtchn[i],
 317                        i % 8 == 0 ? "\n   " : " ");
 318
 319         printk("\nlocally unmasked:\n   ");
 320         for (i = ARRAY_SIZE(sh->evtchn_mask)-1; i >= 0; i--) {
 321                 xen_ulong_t pending = sh->evtchn_pending[i]
 322                         & ~sh->evtchn_mask[i]
 323                         & cpu_evtchn[i];
 324                 printk("%0*"PRI_xen_ulong"%s",
 325                        (int)(sizeof(sh->evtchn_mask[0])*2),
 326                        pending, i % 8 == 0 ? "\n   " : " ");
 327         }
 328
 329         printk("\npending list:\n");
 330         for (i = 0; i < NR_EVENT_CHANNELS; i++) {
 331                 if (sync_test_bit(i, BM(sh->evtchn_pending))) {
 332                         int word_idx = i / BITS_PER_EVTCHN_WORD;
 333                         printk("  %d: event %d -> irq %d%s%s%s\n",
 334                                cpu_from_evtchn(i), i,
 335                                evtchn_to_irq[i],
 336                                sync_test_bit(word_idx, BM(&v->evtchn_pending_sel))
 337                                ? "" : " l2-clear",
 338                                !sync_test_bit(i, BM(sh->evtchn_mask))
 339                                ? "" : " globally-masked",
 340                                sync_test_bit(i, BM(cpu_evtchn))
 341                                ? "" : " locally-masked");
 342                 }
 343         }
 344
 345         spin_unlock_irqrestore(&debug_lock, flags);
 346
 347         return IRQ_HANDLED;
 348 }