accel/tcg/tcg-accel-ops-icount.c

   1 /*
   2  * QEMU TCG Single Threaded vCPUs implementation using instruction counting
   3  *
   4  * Copyright (c) 2003-2008 Fabrice Bellard
   5  * Copyright (c) 2014 Red Hat Inc.
   6  *
   7  * Permission is hereby granted, free of charge, to any person obtaining a copy
   8  * of this software and associated documentation files (the "Software"), to deal
   9  * in the Software without restriction, including without limitation the rights
  10  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  11  * copies of the Software, and to permit persons to whom the Software is
  12  * furnished to do so, subject to the following conditions:
  13  *
  14  * The above copyright notice and this permission notice shall be included in
  15  * all copies or substantial portions of the Software.
  16  *
  17  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  18  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  19  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
  20  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  21  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  22  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  23  * THE SOFTWARE.
  24  */
  25
  26 #include "qemu/osdep.h"
  27 #include "sysemu/replay.h"
  28 #include "sysemu/cpu-timers.h"
  29 #include "qemu/main-loop.h"
  30 #include "qemu/guest-random.h"
  31 #include "exec/exec-all.h"
  32
  33 #include "tcg-accel-ops.h"
  34 #include "tcg-accel-ops-icount.h"
  35 #include "tcg-accel-ops-rr.h"
  36
  37 static int64_t icount_get_limit(void)
  38 {
  39     int64_t deadline;
  40
  41     if (replay_mode != REPLAY_MODE_PLAY) {
  42         /*
  43          * Include all the timers, because they may need an attention.
  44          * Too long CPU execution may create unnecessary delay in UI.
  45          */
  46         deadline = qemu_clock_deadline_ns_all(QEMU_CLOCK_VIRTUAL,
  47                                               QEMU_TIMER_ATTR_ALL);
  48         /* Check realtime timers, because they help with input processing */
  49         deadline = qemu_soonest_timeout(deadline,
  50                 qemu_clock_deadline_ns_all(QEMU_CLOCK_REALTIME,
  51                                            QEMU_TIMER_ATTR_ALL));
  52
  53         /*
  54          * Maintain prior (possibly buggy) behaviour where if no deadline
  55          * was set (as there is no QEMU_CLOCK_VIRTUAL timer) or it is more than
  56          * INT32_MAX nanoseconds ahead, we still use INT32_MAX
  57          * nanoseconds.
  58          */
  59         if ((deadline < 0) || (deadline > INT32_MAX)) {
  60             deadline = INT32_MAX;
  61         }
  62
  63         return icount_round(deadline);
  64     } else {
  65         return replay_get_instructions();
  66     }
  67 }
  68
  69 static void icount_notify_aio_contexts(void)
  70 {
  71     /* Wake up other AioContexts.  */
  72     qemu_clock_notify(QEMU_CLOCK_VIRTUAL);
  73     qemu_clock_run_timers(QEMU_CLOCK_VIRTUAL);
  74 }
  75
  76 void icount_handle_deadline(void)
  77 {
  78     assert(qemu_in_vcpu_thread());
  79     int64_t deadline = qemu_clock_deadline_ns_all(QEMU_CLOCK_VIRTUAL,
  80                                                   QEMU_TIMER_ATTR_ALL);
  81
  82     /*
  83      * Instructions, interrupts, and exceptions are processed in cpu-exec.
  84      * Don't interrupt cpu thread, when these events are waiting
  85      * (i.e., there is no checkpoint)
  86      */
  87     if (deadline == 0) {
  88         icount_notify_aio_contexts();
  89     }
  90 }
  91
  92 /* Distribute the budget evenly across all CPUs */
  93 int64_t icount_percpu_budget(int cpu_count)
  94 {
  95     int64_t limit = icount_get_limit();
  96     int64_t timeslice = limit / cpu_count;
  97
  98     if (timeslice == 0) {
  99         timeslice = limit;
 100     }
 101
 102     return timeslice;
 103 }
 104
 105 void icount_prepare_for_run(CPUState *cpu, int64_t cpu_budget)
 106 {
 107     int insns_left;
 108
 109     /*
 110      * These should always be cleared by icount_process_data after
 111      * each vCPU execution. However u16.high can be raised
 112      * asynchronously by cpu_exit/cpu_interrupt/tcg_handle_interrupt
 113      */
 114     g_assert(cpu_neg(cpu)->icount_decr.u16.low == 0);
 115     g_assert(cpu->icount_extra == 0);
 116
 117     replay_mutex_lock();
 118
 119     cpu->icount_budget = MIN(icount_get_limit(), cpu_budget);
 120     insns_left = MIN(0xffff, cpu->icount_budget);
 121     cpu_neg(cpu)->icount_decr.u16.low = insns_left;
 122     cpu->icount_extra = cpu->icount_budget - insns_left;
 123
 124     if (cpu->icount_budget == 0) {
 125         /*
 126          * We're called without the iothread lock, so must take it while
 127          * we're calling timer handlers.
 128          */
 129         qemu_mutex_lock_iothread();
 130         icount_notify_aio_contexts();
 131         qemu_mutex_unlock_iothread();
 132     }
 133 }
 134
 135 void icount_process_data(CPUState *cpu)
 136 {
 137     /* Account for executed instructions */
 138     icount_update(cpu);
 139
 140     /* Reset the counters */
 141     cpu_neg(cpu)->icount_decr.u16.low = 0;
 142     cpu->icount_extra = 0;
 143     cpu->icount_budget = 0;
 144
 145     replay_account_executed_instructions();
 146
 147     replay_mutex_unlock();
 148 }
 149
 150 void icount_handle_interrupt(CPUState *cpu, int mask)
 151 {
 152     int old_mask = cpu->interrupt_request;
 153
 154     tcg_handle_interrupt(cpu, mask);
 155     if (qemu_cpu_is_self(cpu) &&
 156         !cpu->can_do_io
 157         && (mask & ~old_mask) != 0) {
 158         cpu_abort(cpu, "Raised interrupt while not in I/O function");
 159     }
 160 }