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(evtchn_port_t evtchn, unsigned int cpu,
  56                                   unsigned int old_cpu)
  57 {
  58         clear_bit(evtchn, BM(per_cpu(cpu_evtchn_mask, old_cpu)));
  59         set_bit(evtchn, BM(per_cpu(cpu_evtchn_mask, cpu)));
  60 }
  61
  62 static void evtchn_2l_clear_pending(evtchn_port_t port)
  63 {
  64         struct shared_info *s = HYPERVISOR_shared_info;
  65         sync_clear_bit(port, BM(&s->evtchn_pending[0]));
  66 }
  67
  68 static void evtchn_2l_set_pending(evtchn_port_t port)
  69 {
  70         struct shared_info *s = HYPERVISOR_shared_info;
  71         sync_set_bit(port, BM(&s->evtchn_pending[0]));
  72 }
  73
  74 static bool evtchn_2l_is_pending(evtchn_port_t port)
  75 {
  76         struct shared_info *s = HYPERVISOR_shared_info;
  77         return sync_test_bit(port, BM(&s->evtchn_pending[0]));
  78 }
  79
  80 static void evtchn_2l_mask(evtchn_port_t port)
  81 {
  82         struct shared_info *s = HYPERVISOR_shared_info;
  83         sync_set_bit(port, BM(&s->evtchn_mask[0]));
  84 }
  85
  86 static void evtchn_2l_unmask(evtchn_port_t port)
  87 {
  88         struct shared_info *s = HYPERVISOR_shared_info;
  89         unsigned int cpu = get_cpu();
  90         int do_hypercall = 0, evtchn_pending = 0;
  91
  92         BUG_ON(!irqs_disabled());
  93
  94         smp_wmb();      /* All writes before unmask must be visible. */
  95
  96         if (unlikely((cpu != cpu_from_evtchn(port))))
  97                 do_hypercall = 1;
  98         else {
  99                 /*
 100                  * Need to clear the mask before checking pending to
 101                  * avoid a race with an event becoming pending.
 102                  *
 103                  * EVTCHNOP_unmask will only trigger an upcall if the
 104                  * mask bit was set, so if a hypercall is needed
 105                  * remask the event.
 106                  */
 107                 sync_clear_bit(port, BM(&s->evtchn_mask[0]));
 108                 evtchn_pending = sync_test_bit(port, BM(&s->evtchn_pending[0]));
 109
 110                 if (unlikely(evtchn_pending && xen_hvm_domain())) {
 111                         sync_set_bit(port, BM(&s->evtchn_mask[0]));
 112                         do_hypercall = 1;
 113                 }
 114         }
 115
 116         /* Slow path (hypercall) if this is a non-local port or if this is
 117          * an hvm domain and an event is pending (hvm domains don't have
 118          * their own implementation of irq_enable). */
 119         if (do_hypercall) {
 120                 struct evtchn_unmask unmask = { .port = port };
 121                 (void)HYPERVISOR_event_channel_op(EVTCHNOP_unmask, &unmask);
 122         } else {
 123                 struct vcpu_info *vcpu_info = __this_cpu_read(xen_vcpu);
 124
 125                 /*
 126                  * The following is basically the equivalent of
 127                  * 'hw_resend_irq'. Just like a real IO-APIC we 'lose
 128                  * the interrupt edge' if the channel is masked.
 129                  */
 130                 if (evtchn_pending &&
 131                     !sync_test_and_set_bit(port / BITS_PER_EVTCHN_WORD,
 132                                            BM(&vcpu_info->evtchn_pending_sel)))
 133                         vcpu_info->evtchn_upcall_pending = 1;
 134         }
 135
 136         put_cpu();
 137 }
 138
 139 static DEFINE_PER_CPU(unsigned int, current_word_idx);
 140 static DEFINE_PER_CPU(unsigned int, current_bit_idx);
 141
 142 /*
 143  * Mask out the i least significant bits of w
 144  */
 145 #define MASK_LSBS(w, i) (w & ((~((xen_ulong_t)0UL)) << i))
 146
 147 static inline xen_ulong_t active_evtchns(unsigned int cpu,
 148                                          struct shared_info *sh,
 149                                          unsigned int idx)
 150 {
 151         return sh->evtchn_pending[idx] &
 152                 per_cpu(cpu_evtchn_mask, cpu)[idx] &
 153                 ~sh->evtchn_mask[idx];
 154 }
 155
 156 /*
 157  * Search the CPU's pending events bitmasks.  For each one found, map
 158  * the event number to an irq, and feed it into do_IRQ() for handling.
 159  *
 160  * Xen uses a two-level bitmap to speed searching.  The first level is
 161  * a bitset of words which contain pending event bits.  The second
 162  * level is a bitset of pending events themselves.
 163  */
 164 static void evtchn_2l_handle_events(unsigned cpu, struct evtchn_loop_ctrl *ctrl)
 165 {
 166         int irq;
 167         xen_ulong_t pending_words;
 168         xen_ulong_t pending_bits;
 169         int start_word_idx, start_bit_idx;
 170         int word_idx, bit_idx;
 171         int i;
 172         struct shared_info *s = HYPERVISOR_shared_info;
 173         struct vcpu_info *vcpu_info = __this_cpu_read(xen_vcpu);
 174
 175         /* Timer interrupt has highest priority. */
 176         irq = irq_from_virq(cpu, VIRQ_TIMER);
 177         if (irq != -1) {
 178                 evtchn_port_t evtchn = evtchn_from_irq(irq);
 179                 word_idx = evtchn / BITS_PER_LONG;
 180                 bit_idx = evtchn % BITS_PER_LONG;
 181                 if (active_evtchns(cpu, s, word_idx) & (1ULL << bit_idx))
 182                         generic_handle_irq(irq);
 183         }
 184
 185         /*
 186          * Master flag must be cleared /before/ clearing
 187          * selector flag. xchg_xen_ulong must contain an
 188          * appropriate barrier.
 189          */
 190         pending_words = xchg_xen_ulong(&vcpu_info->evtchn_pending_sel, 0);
 191
 192         start_word_idx = __this_cpu_read(current_word_idx);
 193         start_bit_idx = __this_cpu_read(current_bit_idx);
 194
 195         word_idx = start_word_idx;
 196
 197         for (i = 0; pending_words != 0; i++) {
 198                 xen_ulong_t words;
 199
 200                 words = MASK_LSBS(pending_words, word_idx);
 201
 202                 /*
 203                  * If we masked out all events, wrap to beginning.
 204                  */
 205                 if (words == 0) {
 206                         word_idx = 0;
 207                         bit_idx = 0;
 208                         continue;
 209                 }
 210                 word_idx = EVTCHN_FIRST_BIT(words);
 211
 212                 pending_bits = active_evtchns(cpu, s, word_idx);
 213                 bit_idx = 0; /* usually scan entire word from start */
 214                 /*
 215                  * We scan the starting word in two parts.
 216                  *
 217                  * 1st time: start in the middle, scanning the
 218                  * upper bits.
 219                  *
 220                  * 2nd time: scan the whole word (not just the
 221                  * parts skipped in the first pass) -- if an
 222                  * event in the previously scanned bits is
 223                  * pending again it would just be scanned on
 224                  * the next loop anyway.
 225                  */
 226                 if (word_idx == start_word_idx) {
 227                         if (i == 0)
 228                                 bit_idx = start_bit_idx;
 229                 }
 230
 231                 do {
 232                         xen_ulong_t bits;
 233                         evtchn_port_t port;
 234
 235                         bits = MASK_LSBS(pending_bits, bit_idx);
 236
 237                         /* If we masked out all events, move on. */
 238                         if (bits == 0)
 239                                 break;
 240
 241                         bit_idx = EVTCHN_FIRST_BIT(bits);
 242
 243                         /* Process port. */
 244                         port = (word_idx * BITS_PER_EVTCHN_WORD) + bit_idx;
 245                         handle_irq_for_port(port, ctrl);
 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 int evtchn_2l_percpu_deinit(unsigned int cpu)
 358 {
 359         memset(per_cpu(cpu_evtchn_mask, cpu), 0, sizeof(xen_ulong_t) *
 360                         EVTCHN_2L_NR_CHANNELS/BITS_PER_EVTCHN_WORD);
 361
 362         return 0;
 363 }
 364
 365 static const struct evtchn_ops evtchn_ops_2l = {
 366         .max_channels      = evtchn_2l_max_channels,
 367         .nr_channels       = evtchn_2l_max_channels,
 368         .remove            = evtchn_2l_remove,
 369         .bind_to_cpu       = evtchn_2l_bind_to_cpu,
 370         .clear_pending     = evtchn_2l_clear_pending,
 371         .set_pending       = evtchn_2l_set_pending,
 372         .is_pending        = evtchn_2l_is_pending,
 373         .mask              = evtchn_2l_mask,
 374         .unmask            = evtchn_2l_unmask,
 375         .handle_events     = evtchn_2l_handle_events,
 376         .resume            = evtchn_2l_resume,
 377         .percpu_deinit     = evtchn_2l_percpu_deinit,
 378 };
 379
 380 void __init xen_evtchn_2l_init(void)
 381 {
 382         pr_info("Using 2-level ABI\n");
 383         evtchn_ops = &evtchn_ops_2l;
 384 }