diff options
Diffstat (limited to 'cpus.c')
| -rw-r--r-- | cpus.c | 144 |
1 files changed, 107 insertions, 37 deletions
@@ -37,6 +37,7 @@ #include "sysemu/qtest.h" #include "qemu/main-loop.h" #include "qemu/bitmap.h" +#include "qemu/seqlock.h" #ifndef _WIN32 #include "qemu/compatfd.h" @@ -97,21 +98,32 @@ static bool all_cpu_threads_idle(void) /***********************************************************/ /* guest cycle counter */ +/* Protected by TimersState seqlock */ + +/* Compensate for varying guest execution speed. */ +static int64_t qemu_icount_bias; +static int64_t vm_clock_warp_start; /* 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 -/* Compensate for varying guest execution speed. */ -static int64_t qemu_icount_bias; + +/* Only written by TCG thread */ +static int64_t qemu_icount; + static QEMUTimer *icount_rt_timer; static QEMUTimer *icount_vm_timer; static QEMUTimer *icount_warp_timer; -static int64_t vm_clock_warp_start; -static int64_t qemu_icount; typedef struct TimersState { + /* Protected by BQL. */ 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. + */ + QemuSeqLock vm_clock_seqlock; int64_t cpu_clock_offset; int32_t cpu_ticks_enabled; int64_t dummy; @@ -120,7 +132,7 @@ typedef struct TimersState { static TimersState timers_state; /* Return the virtual CPU time, based on the instruction counter. */ -int64_t cpu_get_icount(void) +static int64_t cpu_get_icount_locked(void) { int64_t icount; CPUState *cpu = current_cpu; @@ -136,7 +148,21 @@ int64_t cpu_get_icount(void) return qemu_icount_bias + (icount << icount_time_shift); } +int64_t cpu_get_icount(void) +{ + int64_t icount; + unsigned start; + + do { + start = seqlock_read_begin(&timers_state.vm_clock_seqlock); + icount = cpu_get_icount_locked(); + } while (seqlock_read_retry(&timers_state.vm_clock_seqlock, start)); + + return icount; +} + /* return the host CPU cycle counter and handle stop/restart */ +/* Caller must hold the BQL */ int64_t cpu_get_ticks(void) { if (use_icount) { @@ -157,37 +183,63 @@ int64_t cpu_get_ticks(void) } } -/* return the host CPU monotonic timer and handle stop/restart */ -int64_t cpu_get_clock(void) +static int64_t cpu_get_clock_locked(void) { int64_t ti; + if (!timers_state.cpu_ticks_enabled) { - return timers_state.cpu_clock_offset; + ti = timers_state.cpu_clock_offset; } else { ti = get_clock(); - return ti + timers_state.cpu_clock_offset; + ti += timers_state.cpu_clock_offset; } + + return ti; } -/* enable cpu_get_ticks() */ +/* return the host CPU monotonic timer and handle stop/restart */ +int64_t cpu_get_clock(void) +{ + int64_t ti; + unsigned start; + + do { + start = seqlock_read_begin(&timers_state.vm_clock_seqlock); + ti = cpu_get_clock_locked(); + } while (seqlock_read_retry(&timers_state.vm_clock_seqlock, start)); + + return ti; +} + +/* enable cpu_get_ticks() + * Caller must hold BQL which server as mutex for vm_clock_seqlock. + */ void cpu_enable_ticks(void) { + /* Here, the really thing protected by seqlock is cpu_clock_offset. */ + seqlock_write_lock(&timers_state.vm_clock_seqlock); if (!timers_state.cpu_ticks_enabled) { timers_state.cpu_ticks_offset -= cpu_get_real_ticks(); timers_state.cpu_clock_offset -= get_clock(); timers_state.cpu_ticks_enabled = 1; } + seqlock_write_unlock(&timers_state.vm_clock_seqlock); } /* disable cpu_get_ticks() : the clock is stopped. You must not call - cpu_get_ticks() after that. */ + * cpu_get_ticks() after that. + * Caller must hold BQL which server as mutex for vm_clock_seqlock. + */ void cpu_disable_ticks(void) { + /* Here, the really thing protected by seqlock is cpu_clock_offset. */ + seqlock_write_lock(&timers_state.vm_clock_seqlock); if (timers_state.cpu_ticks_enabled) { timers_state.cpu_ticks_offset = cpu_get_ticks(); - timers_state.cpu_clock_offset = cpu_get_clock(); + timers_state.cpu_clock_offset = cpu_get_clock_locked(); timers_state.cpu_ticks_enabled = 0; } + seqlock_write_unlock(&timers_state.vm_clock_seqlock); } /* Correlation between real and virtual time is always going to be @@ -201,13 +253,19 @@ static void icount_adjust(void) int64_t cur_time; int64_t cur_icount; int64_t delta; + + /* Protected by TimersState mutex. */ static int64_t last_delta; + /* If the VM is not running, then do nothing. */ if (!runstate_is_running()) { return; } - cur_time = cpu_get_clock(); - cur_icount = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL); + + seqlock_write_lock(&timers_state.vm_clock_seqlock); + cur_time = cpu_get_clock_locked(); + cur_icount = cpu_get_icount_locked(); + delta = cur_icount - cur_time; /* FIXME: This is a very crude algorithm, somewhat prone to oscillation. */ if (delta > 0 @@ -224,6 +282,7 @@ static void icount_adjust(void) } last_delta = delta; qemu_icount_bias = cur_icount - (qemu_icount << icount_time_shift); + seqlock_write_unlock(&timers_state.vm_clock_seqlock); } static void icount_adjust_rt(void *opaque) @@ -248,30 +307,37 @@ static int64_t qemu_icount_round(int64_t count) static void icount_warp_rt(void *opaque) { - if (vm_clock_warp_start == -1) { + /* The icount_warp_timer is rescheduled soon after vm_clock_warp_start + * changes from -1 to another value, so the race here is okay. + */ + if (atomic_read(&vm_clock_warp_start) == -1) { return; } + seqlock_write_lock(&timers_state.vm_clock_seqlock); if (runstate_is_running()) { int64_t clock = qemu_clock_get_ns(QEMU_CLOCK_REALTIME); - int64_t warp_delta = clock - vm_clock_warp_start; - if (use_icount == 1) { - qemu_icount_bias += warp_delta; - } else { + int64_t warp_delta; + + warp_delta = clock - vm_clock_warp_start; + if (use_icount == 2) { /* * In adaptive mode, do not let QEMU_CLOCK_VIRTUAL run too * far ahead of real time. */ - int64_t cur_time = cpu_get_clock(); - int64_t cur_icount = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL); + int64_t cur_time = cpu_get_clock_locked(); + int64_t cur_icount = cpu_get_icount_locked(); int64_t delta = cur_time - cur_icount; - qemu_icount_bias += MIN(warp_delta, delta); - } - if (qemu_clock_expired(QEMU_CLOCK_VIRTUAL)) { - qemu_clock_notify(QEMU_CLOCK_VIRTUAL); + warp_delta = MIN(warp_delta, delta); } + qemu_icount_bias += warp_delta; } vm_clock_warp_start = -1; + seqlock_write_unlock(&timers_state.vm_clock_seqlock); + + if (qemu_clock_expired(QEMU_CLOCK_VIRTUAL)) { + qemu_clock_notify(QEMU_CLOCK_VIRTUAL); + } } void qtest_clock_warp(int64_t dest) @@ -281,7 +347,10 @@ void qtest_clock_warp(int64_t dest) while (clock < dest) { int64_t deadline = qemu_clock_deadline_ns_all(QEMU_CLOCK_VIRTUAL); int64_t warp = MIN(dest - clock, deadline); + seqlock_write_lock(&timers_state.vm_clock_seqlock); qemu_icount_bias += warp; + seqlock_write_unlock(&timers_state.vm_clock_seqlock); + qemu_clock_run_timers(QEMU_CLOCK_VIRTUAL); clock = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL); } @@ -290,6 +359,7 @@ void qtest_clock_warp(int64_t dest) void qemu_clock_warp(QEMUClockType type) { + int64_t clock; int64_t deadline; /* @@ -309,8 +379,8 @@ void qemu_clock_warp(QEMUClockType type) * the earliest QEMU_CLOCK_VIRTUAL timer. */ icount_warp_rt(NULL); - if (!all_cpu_threads_idle() || !qemu_clock_has_timers(QEMU_CLOCK_VIRTUAL)) { - timer_del(icount_warp_timer); + timer_del(icount_warp_timer); + if (!all_cpu_threads_idle()) { return; } @@ -319,17 +389,11 @@ void qemu_clock_warp(QEMUClockType type) return; } - vm_clock_warp_start = qemu_clock_get_ns(QEMU_CLOCK_REALTIME); /* We want to use the earliest deadline from ALL vm_clocks */ + clock = qemu_clock_get_ns(QEMU_CLOCK_REALTIME); deadline = qemu_clock_deadline_ns_all(QEMU_CLOCK_VIRTUAL); - - /* Maintain prior (possibly buggy) behaviour where if no deadline - * was set (as there is no QEMU_CLOCK_VIRTUAL timer) or it is more than - * INT32_MAX nanoseconds ahead, we still use INT32_MAX - * nanoseconds. - */ - if ((deadline < 0) || (deadline > INT32_MAX)) { - deadline = INT32_MAX; + if (deadline < 0) { + return; } if (deadline > 0) { @@ -350,7 +414,12 @@ void qemu_clock_warp(QEMUClockType type) * you will not be sending network packets continuously instead of * every 100ms. */ - timer_mod(icount_warp_timer, vm_clock_warp_start + deadline); + seqlock_write_lock(&timers_state.vm_clock_seqlock); + if (vm_clock_warp_start == -1 || vm_clock_warp_start > clock) { + vm_clock_warp_start = clock; + } + seqlock_write_unlock(&timers_state.vm_clock_seqlock); + timer_mod_anticipate(icount_warp_timer, clock + deadline); } else if (deadline == 0) { qemu_clock_notify(QEMU_CLOCK_VIRTUAL); } @@ -371,6 +440,7 @@ static const VMStateDescription vmstate_timers = { void configure_icount(const char *option) { + seqlock_init(&timers_state.vm_clock_seqlock, NULL); vmstate_register(NULL, 0, &vmstate_timers, &timers_state); if (!option) { return; |