system/cpu-timers.c

   1 /*
   2  * QEMU System Emulator
   3  *
   4  * Copyright (c) 2003-2008 Fabrice Bellard
   5  *
   6  * Permission is hereby granted, free of charge, to any person obtaining a copy
   7  * of this software and associated documentation files (the "Software"), to deal
   8  * in the Software without restriction, including without limitation the rights
   9  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  10  * copies of the Software, and to permit persons to whom the Software is
  11  * furnished to do so, subject to the following conditions:
  12  *
  13  * The above copyright notice and this permission notice shall be included in
  14  * all copies or substantial portions of the Software.
  15  *
  16  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  17  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  18  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
  19  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  20  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  21  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  22  * THE SOFTWARE.
  23  */
  24
  25 #include "qemu/osdep.h"
  26 #include "qemu/cutils.h"
  27 #include "migration/vmstate.h"
  28 #include "qapi/error.h"
  29 #include "qemu/error-report.h"
  30 #include "sysemu/cpus.h"
  31 #include "qemu/main-loop.h"
  32 #include "qemu/option.h"
  33 #include "qemu/seqlock.h"
  34 #include "sysemu/replay.h"
  35 #include "sysemu/runstate.h"
  36 #include "hw/core/cpu.h"
  37 #include "sysemu/cpu-timers.h"
  38 #include "sysemu/cpu-throttle.h"
  39 #include "sysemu/cpu-timers-internal.h"
  40
  41 /* clock and ticks */
  42
  43 static int64_t cpu_get_ticks_locked(void)
  44 {
  45     int64_t ticks = timers_state.cpu_ticks_offset;
  46     if (timers_state.cpu_ticks_enabled) {
  47         ticks += cpu_get_host_ticks();
  48     }
  49
  50     if (timers_state.cpu_ticks_prev > ticks) {
  51         /* Non increasing ticks may happen if the host uses software suspend. */
  52         timers_state.cpu_ticks_offset += timers_state.cpu_ticks_prev - ticks;
  53         ticks = timers_state.cpu_ticks_prev;
  54     }
  55
  56     timers_state.cpu_ticks_prev = ticks;
  57     return ticks;
  58 }
  59
  60 /*
  61  * return the time elapsed in VM between vm_start and vm_stop.
  62  * cpu_get_ticks() uses units of the host CPU cycle counter.
  63  */
  64 int64_t cpu_get_ticks(void)
  65 {
  66     int64_t ticks;
  67
  68     qemu_spin_lock(&timers_state.vm_clock_lock);
  69     ticks = cpu_get_ticks_locked();
  70     qemu_spin_unlock(&timers_state.vm_clock_lock);
  71     return ticks;
  72 }
  73
  74 int64_t cpu_get_clock_locked(void)
  75 {
  76     int64_t time;
  77
  78     time = timers_state.cpu_clock_offset;
  79     if (timers_state.cpu_ticks_enabled) {
  80         time += get_clock();
  81     }
  82
  83     return time;
  84 }
  85
  86 /*
  87  * Return the monotonic time elapsed in VM, i.e.,
  88  * the time between vm_start and vm_stop
  89  */
  90 int64_t cpu_get_clock(void)
  91 {
  92     int64_t ti;
  93     unsigned start;
  94
  95     do {
  96         start = seqlock_read_begin(&timers_state.vm_clock_seqlock);
  97         ti = cpu_get_clock_locked();
  98     } while (seqlock_read_retry(&timers_state.vm_clock_seqlock, start));
  99
 100     return ti;
 101 }
 102
 103 /*
 104  * enable cpu_get_ticks()
 105  * Caller must hold BQL which serves as mutex for vm_clock_seqlock.
 106  */
 107 void cpu_enable_ticks(void)
 108 {
 109     seqlock_write_lock(&timers_state.vm_clock_seqlock,
 110                        &timers_state.vm_clock_lock);
 111     if (!timers_state.cpu_ticks_enabled) {
 112         timers_state.cpu_ticks_offset -= cpu_get_host_ticks();
 113         timers_state.cpu_clock_offset -= get_clock();
 114         timers_state.cpu_ticks_enabled = 1;
 115     }
 116     seqlock_write_unlock(&timers_state.vm_clock_seqlock,
 117                        &timers_state.vm_clock_lock);
 118 }
 119
 120 /*
 121  * disable cpu_get_ticks() : the clock is stopped. You must not call
 122  * cpu_get_ticks() after that.
 123  * Caller must hold BQL which serves as mutex for vm_clock_seqlock.
 124  */
 125 void cpu_disable_ticks(void)
 126 {
 127     seqlock_write_lock(&timers_state.vm_clock_seqlock,
 128                        &timers_state.vm_clock_lock);
 129     if (timers_state.cpu_ticks_enabled) {
 130         timers_state.cpu_ticks_offset += cpu_get_host_ticks();
 131         timers_state.cpu_clock_offset = cpu_get_clock_locked();
 132         timers_state.cpu_ticks_enabled = 0;
 133     }
 134     seqlock_write_unlock(&timers_state.vm_clock_seqlock,
 135                          &timers_state.vm_clock_lock);
 136 }
 137
 138 static bool icount_state_needed(void *opaque)
 139 {
 140     return icount_enabled();
 141 }
 142
 143 static bool warp_timer_state_needed(void *opaque)
 144 {
 145     TimersState *s = opaque;
 146     return s->icount_warp_timer != NULL;
 147 }
 148
 149 static bool adjust_timers_state_needed(void *opaque)
 150 {
 151     TimersState *s = opaque;
 152     return s->icount_rt_timer != NULL;
 153 }
 154
 155 static bool icount_shift_state_needed(void *opaque)
 156 {
 157     return icount_enabled() == 2;
 158 }
 159
 160 /*
 161  * Subsection for warp timer migration is optional, because may not be created
 162  */
 163 static const VMStateDescription icount_vmstate_warp_timer = {
 164     .name = "timer/icount/warp_timer",
 165     .version_id = 1,
 166     .minimum_version_id = 1,
 167     .needed = warp_timer_state_needed,
 168     .fields = (VMStateField[]) {
 169         VMSTATE_INT64(vm_clock_warp_start, TimersState),
 170         VMSTATE_TIMER_PTR(icount_warp_timer, TimersState),
 171         VMSTATE_END_OF_LIST()
 172     }
 173 };
 174
 175 static const VMStateDescription icount_vmstate_adjust_timers = {
 176     .name = "timer/icount/timers",
 177     .version_id = 1,
 178     .minimum_version_id = 1,
 179     .needed = adjust_timers_state_needed,
 180     .fields = (VMStateField[]) {
 181         VMSTATE_TIMER_PTR(icount_rt_timer, TimersState),
 182         VMSTATE_TIMER_PTR(icount_vm_timer, TimersState),
 183         VMSTATE_END_OF_LIST()
 184     }
 185 };
 186
 187 static const VMStateDescription icount_vmstate_shift = {
 188     .name = "timer/icount/shift",
 189     .version_id = 2,
 190     .minimum_version_id = 2,
 191     .needed = icount_shift_state_needed,
 192     .fields = (VMStateField[]) {
 193         VMSTATE_INT16(icount_time_shift, TimersState),
 194         VMSTATE_INT64(last_delta, TimersState),
 195         VMSTATE_END_OF_LIST()
 196     }
 197 };
 198
 199 /*
 200  * This is a subsection for icount migration.
 201  */
 202 static const VMStateDescription icount_vmstate_timers = {
 203     .name = "timer/icount",
 204     .version_id = 1,
 205     .minimum_version_id = 1,
 206     .needed = icount_state_needed,
 207     .fields = (VMStateField[]) {
 208         VMSTATE_INT64(qemu_icount_bias, TimersState),
 209         VMSTATE_INT64(qemu_icount, TimersState),
 210         VMSTATE_END_OF_LIST()
 211     },
 212     .subsections = (const VMStateDescription * []) {
 213         &icount_vmstate_warp_timer,
 214         &icount_vmstate_adjust_timers,
 215         &icount_vmstate_shift,
 216         NULL
 217     }
 218 };
 219
 220 static const VMStateDescription vmstate_timers = {
 221     .name = "timer",
 222     .version_id = 2,
 223     .minimum_version_id = 1,
 224     .fields = (VMStateField[]) {
 225         VMSTATE_INT64(cpu_ticks_offset, TimersState),
 226         VMSTATE_UNUSED(8),
 227         VMSTATE_INT64_V(cpu_clock_offset, TimersState, 2),
 228         VMSTATE_END_OF_LIST()
 229     },
 230     .subsections = (const VMStateDescription * []) {
 231         &icount_vmstate_timers,
 232         NULL
 233     }
 234 };
 235
 236 static void do_nothing(CPUState *cpu, run_on_cpu_data unused)
 237 {
 238 }
 239
 240 void qemu_timer_notify_cb(void *opaque, QEMUClockType type)
 241 {
 242     if (!icount_enabled() || type != QEMU_CLOCK_VIRTUAL) {
 243         qemu_notify_event();
 244         return;
 245     }
 246
 247     if (qemu_in_vcpu_thread()) {
 248         /*
 249          * A CPU is currently running; kick it back out to the
 250          * tcg_cpu_exec() loop so it will recalculate its
 251          * icount deadline immediately.
 252          */
 253         qemu_cpu_kick(current_cpu);
 254     } else if (first_cpu) {
 255         /*
 256          * qemu_cpu_kick is not enough to kick a halted CPU out of
 257          * qemu_tcg_wait_io_event.  async_run_on_cpu, instead,
 258          * causes cpu_thread_is_idle to return false.  This way,
 259          * handle_icount_deadline can run.
 260          * If we have no CPUs at all for some reason, we don't
 261          * need to do anything.
 262          */
 263         async_run_on_cpu(first_cpu, do_nothing, RUN_ON_CPU_NULL);
 264     }
 265 }
 266
 267 TimersState timers_state;
 268
 269 /* initialize timers state and the cpu throttle for convenience */
 270 void cpu_timers_init(void)
 271 {
 272     seqlock_init(&timers_state.vm_clock_seqlock);
 273     qemu_spin_init(&timers_state.vm_clock_lock);
 274     vmstate_register(NULL, 0, &vmstate_timers, &timers_state);
 275
 276     cpu_throttle_init();
 277 }