diff options
Diffstat (limited to 'cpus.c')
| -rw-r--r-- | cpus.c | 186 |
1 files changed, 117 insertions, 69 deletions
@@ -121,8 +121,6 @@ static bool all_cpu_threads_idle(void) /* Protected by TimersState seqlock */ static bool icount_sleep = true; -/* Conversion factor from emulated instructions to virtual clock ticks. */ -static int icount_time_shift; /* Arbitrarily pick 1MIPS as the minimum allowable speed. */ #define MAX_ICOUNT_SHIFT 10 @@ -131,20 +129,27 @@ typedef struct TimersState { int64_t cpu_ticks_prev; int64_t cpu_ticks_offset; - /* cpu_clock_offset can be read out of BQL, so protect it with - * this lock. + /* Protect fields that can be respectively read outside the + * BQL, and written from multiple threads. */ QemuSeqLock vm_clock_seqlock; - int64_t cpu_clock_offset; - int32_t cpu_ticks_enabled; - int64_t dummy; + QemuSpin vm_clock_lock; + + int16_t cpu_ticks_enabled; + + /* Conversion factor from emulated instructions to virtual clock ticks. */ + int16_t icount_time_shift; /* Compensate for varying guest execution speed. */ int64_t qemu_icount_bias; + + int64_t vm_clock_warp_start; + int64_t cpu_clock_offset; + /* Only written by TCG thread */ int64_t qemu_icount; + /* for adjusting icount */ - int64_t vm_clock_warp_start; QEMUTimer *icount_rt_timer; QEMUTimer *icount_vm_timer; QEMUTimer *icount_warp_timer; @@ -245,16 +250,19 @@ void cpu_update_icount(CPUState *cpu) int64_t executed = cpu_get_icount_executed(cpu); cpu->icount_budget -= executed; -#ifdef CONFIG_ATOMIC64 +#ifndef CONFIG_ATOMIC64 + seqlock_write_lock(&timers_state.vm_clock_seqlock, + &timers_state.vm_clock_lock); +#endif atomic_set__nocheck(&timers_state.qemu_icount, - atomic_read__nocheck(&timers_state.qemu_icount) + - executed); -#else /* FIXME: we need 64bit atomics to do this safely */ - timers_state.qemu_icount += executed; + timers_state.qemu_icount + executed); +#ifndef CONFIG_ATOMIC64 + seqlock_write_unlock(&timers_state.vm_clock_seqlock, + &timers_state.vm_clock_lock); #endif } -int64_t cpu_get_icount_raw(void) +static int64_t cpu_get_icount_raw_locked(void) { CPUState *cpu = current_cpu; @@ -266,20 +274,30 @@ int64_t cpu_get_icount_raw(void) /* Take into account what has run */ cpu_update_icount(cpu); } -#ifdef CONFIG_ATOMIC64 + /* The read is protected by the seqlock, so __nocheck is okay. */ return atomic_read__nocheck(&timers_state.qemu_icount); -#else /* FIXME: we need 64bit atomics to do this safely */ - return timers_state.qemu_icount; -#endif } -/* Return the virtual CPU time, based on the instruction counter. */ static int64_t cpu_get_icount_locked(void) { - int64_t icount = cpu_get_icount_raw(); - return timers_state.qemu_icount_bias + cpu_icount_to_ns(icount); + int64_t icount = cpu_get_icount_raw_locked(); + return atomic_read__nocheck(&timers_state.qemu_icount_bias) + cpu_icount_to_ns(icount); } +int64_t cpu_get_icount_raw(void) +{ + int64_t icount; + unsigned start; + + do { + start = seqlock_read_begin(&timers_state.vm_clock_seqlock); + icount = cpu_get_icount_raw_locked(); + } while (seqlock_read_retry(&timers_state.vm_clock_seqlock, start)); + + return icount; +} + +/* Return the virtual CPU time, based on the instruction counter. */ int64_t cpu_get_icount(void) { int64_t icount; @@ -295,14 +313,29 @@ int64_t cpu_get_icount(void) int64_t cpu_icount_to_ns(int64_t icount) { - return icount << icount_time_shift; + return icount << atomic_read(&timers_state.icount_time_shift); +} + +static int64_t cpu_get_ticks_locked(void) +{ + int64_t ticks = timers_state.cpu_ticks_offset; + if (timers_state.cpu_ticks_enabled) { + ticks += cpu_get_host_ticks(); + } + + if (timers_state.cpu_ticks_prev > ticks) { + /* Non increasing ticks may happen if the host uses software suspend. */ + timers_state.cpu_ticks_offset += timers_state.cpu_ticks_prev - ticks; + ticks = timers_state.cpu_ticks_prev; + } + + timers_state.cpu_ticks_prev = ticks; + return ticks; } /* return the time elapsed in VM between vm_start and vm_stop. Unless * icount is active, cpu_get_ticks() uses units of the host CPU cycle * counter. - * - * Caller must hold the BQL */ int64_t cpu_get_ticks(void) { @@ -312,19 +345,9 @@ int64_t cpu_get_ticks(void) return cpu_get_icount(); } - ticks = timers_state.cpu_ticks_offset; - if (timers_state.cpu_ticks_enabled) { - ticks += cpu_get_host_ticks(); - } - - if (timers_state.cpu_ticks_prev > ticks) { - /* Note: non increasing ticks may happen if the host uses - software suspend */ - timers_state.cpu_ticks_offset += timers_state.cpu_ticks_prev - ticks; - ticks = timers_state.cpu_ticks_prev; - } - - timers_state.cpu_ticks_prev = ticks; + qemu_spin_lock(&timers_state.vm_clock_lock); + ticks = cpu_get_ticks_locked(); + qemu_spin_unlock(&timers_state.vm_clock_lock); return ticks; } @@ -361,14 +384,15 @@ int64_t cpu_get_clock(void) */ void cpu_enable_ticks(void) { - /* Here, the really thing protected by seqlock is cpu_clock_offset. */ - seqlock_write_begin(&timers_state.vm_clock_seqlock); + seqlock_write_lock(&timers_state.vm_clock_seqlock, + &timers_state.vm_clock_lock); if (!timers_state.cpu_ticks_enabled) { timers_state.cpu_ticks_offset -= cpu_get_host_ticks(); timers_state.cpu_clock_offset -= get_clock(); timers_state.cpu_ticks_enabled = 1; } - seqlock_write_end(&timers_state.vm_clock_seqlock); + seqlock_write_unlock(&timers_state.vm_clock_seqlock, + &timers_state.vm_clock_lock); } /* disable cpu_get_ticks() : the clock is stopped. You must not call @@ -377,14 +401,15 @@ void cpu_enable_ticks(void) */ void cpu_disable_ticks(void) { - /* Here, the really thing protected by seqlock is cpu_clock_offset. */ - seqlock_write_begin(&timers_state.vm_clock_seqlock); + seqlock_write_lock(&timers_state.vm_clock_seqlock, + &timers_state.vm_clock_lock); if (timers_state.cpu_ticks_enabled) { timers_state.cpu_ticks_offset += cpu_get_host_ticks(); timers_state.cpu_clock_offset = cpu_get_clock_locked(); timers_state.cpu_ticks_enabled = 0; } - seqlock_write_end(&timers_state.vm_clock_seqlock); + seqlock_write_unlock(&timers_state.vm_clock_seqlock, + &timers_state.vm_clock_lock); } /* Correlation between real and virtual time is always going to be @@ -407,7 +432,8 @@ static void icount_adjust(void) return; } - seqlock_write_begin(&timers_state.vm_clock_seqlock); + seqlock_write_lock(&timers_state.vm_clock_seqlock, + &timers_state.vm_clock_lock); cur_time = cpu_get_clock_locked(); cur_icount = cpu_get_icount_locked(); @@ -415,20 +441,24 @@ static void icount_adjust(void) /* FIXME: This is a very crude algorithm, somewhat prone to oscillation. */ if (delta > 0 && last_delta + ICOUNT_WOBBLE < delta * 2 - && icount_time_shift > 0) { + && timers_state.icount_time_shift > 0) { /* The guest is getting too far ahead. Slow time down. */ - icount_time_shift--; + atomic_set(&timers_state.icount_time_shift, + timers_state.icount_time_shift - 1); } if (delta < 0 && last_delta - ICOUNT_WOBBLE > delta * 2 - && icount_time_shift < MAX_ICOUNT_SHIFT) { + && timers_state.icount_time_shift < MAX_ICOUNT_SHIFT) { /* The guest is getting too far behind. Speed time up. */ - icount_time_shift++; + atomic_set(&timers_state.icount_time_shift, + timers_state.icount_time_shift + 1); } last_delta = delta; - timers_state.qemu_icount_bias = cur_icount - - (timers_state.qemu_icount << icount_time_shift); - seqlock_write_end(&timers_state.vm_clock_seqlock); + atomic_set__nocheck(&timers_state.qemu_icount_bias, + cur_icount - (timers_state.qemu_icount + << timers_state.icount_time_shift)); + seqlock_write_unlock(&timers_state.vm_clock_seqlock, + &timers_state.vm_clock_lock); } static void icount_adjust_rt(void *opaque) @@ -448,7 +478,8 @@ static void icount_adjust_vm(void *opaque) static int64_t qemu_icount_round(int64_t count) { - return (count + (1 << icount_time_shift) - 1) >> icount_time_shift; + int shift = atomic_read(&timers_state.icount_time_shift); + return (count + (1 << shift) - 1) >> shift; } static void icount_warp_rt(void) @@ -468,7 +499,8 @@ static void icount_warp_rt(void) return; } - seqlock_write_begin(&timers_state.vm_clock_seqlock); + seqlock_write_lock(&timers_state.vm_clock_seqlock, + &timers_state.vm_clock_lock); if (runstate_is_running()) { int64_t clock = REPLAY_CLOCK(REPLAY_CLOCK_VIRTUAL_RT, cpu_get_clock_locked()); @@ -484,10 +516,12 @@ static void icount_warp_rt(void) int64_t delta = clock - cur_icount; warp_delta = MIN(warp_delta, delta); } - timers_state.qemu_icount_bias += warp_delta; + atomic_set__nocheck(&timers_state.qemu_icount_bias, + timers_state.qemu_icount_bias + warp_delta); } timers_state.vm_clock_warp_start = -1; - seqlock_write_end(&timers_state.vm_clock_seqlock); + seqlock_write_unlock(&timers_state.vm_clock_seqlock, + &timers_state.vm_clock_lock); if (qemu_clock_expired(QEMU_CLOCK_VIRTUAL)) { qemu_clock_notify(QEMU_CLOCK_VIRTUAL); @@ -512,9 +546,12 @@ void qtest_clock_warp(int64_t dest) int64_t deadline = qemu_clock_deadline_ns_all(QEMU_CLOCK_VIRTUAL); int64_t warp = qemu_soonest_timeout(dest - clock, deadline); - seqlock_write_begin(&timers_state.vm_clock_seqlock); - timers_state.qemu_icount_bias += warp; - seqlock_write_end(&timers_state.vm_clock_seqlock); + seqlock_write_lock(&timers_state.vm_clock_seqlock, + &timers_state.vm_clock_lock); + atomic_set__nocheck(&timers_state.qemu_icount_bias, + timers_state.qemu_icount_bias + warp); + seqlock_write_unlock(&timers_state.vm_clock_seqlock, + &timers_state.vm_clock_lock); qemu_clock_run_timers(QEMU_CLOCK_VIRTUAL); timerlist_run_timers(aio_context->tlg.tl[QEMU_CLOCK_VIRTUAL]); @@ -581,9 +618,12 @@ void qemu_start_warp_timer(void) * It is useful when we want a deterministic execution time, * isolated from host latencies. */ - seqlock_write_begin(&timers_state.vm_clock_seqlock); - timers_state.qemu_icount_bias += deadline; - seqlock_write_end(&timers_state.vm_clock_seqlock); + seqlock_write_lock(&timers_state.vm_clock_seqlock, + &timers_state.vm_clock_lock); + atomic_set__nocheck(&timers_state.qemu_icount_bias, + timers_state.qemu_icount_bias + deadline); + seqlock_write_unlock(&timers_state.vm_clock_seqlock, + &timers_state.vm_clock_lock); qemu_clock_notify(QEMU_CLOCK_VIRTUAL); } else { /* @@ -594,12 +634,14 @@ void qemu_start_warp_timer(void) * you will not be sending network packets continuously instead of * every 100ms. */ - seqlock_write_begin(&timers_state.vm_clock_seqlock); + seqlock_write_lock(&timers_state.vm_clock_seqlock, + &timers_state.vm_clock_lock); if (timers_state.vm_clock_warp_start == -1 || timers_state.vm_clock_warp_start > clock) { timers_state.vm_clock_warp_start = clock; } - seqlock_write_end(&timers_state.vm_clock_seqlock); + seqlock_write_unlock(&timers_state.vm_clock_seqlock, + &timers_state.vm_clock_lock); timer_mod_anticipate(timers_state.icount_warp_timer, clock + deadline); } @@ -700,7 +742,7 @@ static const VMStateDescription vmstate_timers = { .minimum_version_id = 1, .fields = (VMStateField[]) { VMSTATE_INT64(cpu_ticks_offset, TimersState), - VMSTATE_INT64(dummy, TimersState), + VMSTATE_UNUSED(8), VMSTATE_INT64_V(cpu_clock_offset, TimersState, 2), VMSTATE_END_OF_LIST() }, @@ -812,7 +854,7 @@ void configure_icount(QemuOpts *opts, Error **errp) } if (strcmp(option, "auto") != 0) { errno = 0; - icount_time_shift = strtol(option, &rem_str, 0); + timers_state.icount_time_shift = strtol(option, &rem_str, 0); if (errno != 0 || *rem_str != '\0' || !strlen(option)) { error_setg(errp, "icount: Invalid shift value"); } @@ -828,7 +870,7 @@ void configure_icount(QemuOpts *opts, Error **errp) /* 125MIPS seems a reasonable initial guess at the guest speed. It will be corrected fairly quickly anyway. */ - icount_time_shift = 3; + timers_state.icount_time_shift = 3; /* Have both realtime and virtual time triggers for speed adjustment. The realtime trigger catches emulated time passing too slowly, @@ -1491,7 +1533,7 @@ static void *qemu_tcg_rr_cpu_thread_fn(void *arg) atomic_mb_set(&cpu->exit_request, 0); } - qemu_tcg_rr_wait_io_event(cpu ? cpu : QTAILQ_FIRST(&cpus)); + qemu_tcg_rr_wait_io_event(cpu ? cpu : first_cpu); deal_with_unplugged_cpus(); } @@ -1762,10 +1804,16 @@ bool qemu_mutex_iothread_locked(void) return iothread_locked; } -void qemu_mutex_lock_iothread(void) +/* + * The BQL is taken from so many places that it is worth profiling the + * callers directly, instead of funneling them all through a single function. + */ +void qemu_mutex_lock_iothread_impl(const char *file, int line) { + QemuMutexLockFunc bql_lock = atomic_read(&qemu_bql_mutex_lock_func); + g_assert(!qemu_mutex_iothread_locked()); - qemu_mutex_lock(&qemu_global_mutex); + bql_lock(&qemu_global_mutex, file, line); iothread_locked = true; } |