diff options
Diffstat (limited to 'cpus.c')
| -rw-r--r-- | cpus.c | 295 |
1 files changed, 277 insertions, 18 deletions
@@ -65,6 +65,281 @@ static CPUState *next_cpu; /***********************************************************/ +/* guest cycle counter */ + +/* 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; +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 { + int64_t cpu_ticks_prev; + int64_t cpu_ticks_offset; + int64_t cpu_clock_offset; + int32_t cpu_ticks_enabled; + int64_t dummy; +} TimersState; + +TimersState timers_state; + +/* Return the virtual CPU time, based on the instruction counter. */ +int64_t cpu_get_icount(void) +{ + int64_t icount; + CPUState *env = cpu_single_env;; + + icount = qemu_icount; + if (env) { + if (!can_do_io(env)) { + fprintf(stderr, "Bad clock read\n"); + } + icount -= (env->icount_decr.u16.low + env->icount_extra); + } + return qemu_icount_bias + (icount << icount_time_shift); +} + +/* return the host CPU cycle counter and handle stop/restart */ +int64_t cpu_get_ticks(void) +{ + if (use_icount) { + return cpu_get_icount(); + } + if (!timers_state.cpu_ticks_enabled) { + return timers_state.cpu_ticks_offset; + } else { + int64_t ticks; + ticks = cpu_get_real_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; + } + timers_state.cpu_ticks_prev = ticks; + return ticks + timers_state.cpu_ticks_offset; + } +} + +/* return the host CPU monotonic timer and handle stop/restart */ +int64_t cpu_get_clock(void) +{ + int64_t ti; + if (!timers_state.cpu_ticks_enabled) { + return timers_state.cpu_clock_offset; + } else { + ti = get_clock(); + return ti + timers_state.cpu_clock_offset; + } +} + +/* enable cpu_get_ticks() */ +void cpu_enable_ticks(void) +{ + 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; + } +} + +/* disable cpu_get_ticks() : the clock is stopped. You must not call + cpu_get_ticks() after that. */ +void cpu_disable_ticks(void) +{ + 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_ticks_enabled = 0; + } +} + +/* Correlation between real and virtual time is always going to be + fairly approximate, so ignore small variation. + When the guest is idle real and virtual time will be aligned in + the IO wait loop. */ +#define ICOUNT_WOBBLE (get_ticks_per_sec() / 10) + +static void icount_adjust(void) +{ + int64_t cur_time; + int64_t cur_icount; + int64_t delta; + 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_get_clock_ns(vm_clock); + delta = cur_icount - cur_time; + /* FIXME: This is a very crude algorithm, somewhat prone to oscillation. */ + if (delta > 0 + && last_delta + ICOUNT_WOBBLE < delta * 2 + && icount_time_shift > 0) { + /* The guest is getting too far ahead. Slow time down. */ + icount_time_shift--; + } + if (delta < 0 + && last_delta - ICOUNT_WOBBLE > delta * 2 + && icount_time_shift < MAX_ICOUNT_SHIFT) { + /* The guest is getting too far behind. Speed time up. */ + icount_time_shift++; + } + last_delta = delta; + qemu_icount_bias = cur_icount - (qemu_icount << icount_time_shift); +} + +static void icount_adjust_rt(void *opaque) +{ + qemu_mod_timer(icount_rt_timer, + qemu_get_clock_ms(rt_clock) + 1000); + icount_adjust(); +} + +static void icount_adjust_vm(void *opaque) +{ + qemu_mod_timer(icount_vm_timer, + qemu_get_clock_ns(vm_clock) + get_ticks_per_sec() / 10); + icount_adjust(); +} + +static int64_t qemu_icount_round(int64_t count) +{ + return (count + (1 << icount_time_shift) - 1) >> icount_time_shift; +} + +static void icount_warp_rt(void *opaque) +{ + if (vm_clock_warp_start == -1) { + return; + } + + if (runstate_is_running()) { + int64_t clock = qemu_get_clock_ns(rt_clock); + int64_t warp_delta = clock - vm_clock_warp_start; + if (use_icount == 1) { + qemu_icount_bias += warp_delta; + } else { + /* + * In adaptive mode, do not let the vm_clock run too + * far ahead of real time. + */ + int64_t cur_time = cpu_get_clock(); + int64_t cur_icount = qemu_get_clock_ns(vm_clock); + int64_t delta = cur_time - cur_icount; + qemu_icount_bias += MIN(warp_delta, delta); + } + if (qemu_clock_expired(vm_clock)) { + qemu_notify_event(); + } + } + vm_clock_warp_start = -1; +} + +void qemu_clock_warp(QEMUClock *clock) +{ + int64_t deadline; + + /* + * There are too many global variables to make the "warp" behavior + * applicable to other clocks. But a clock argument removes the + * need for if statements all over the place. + */ + if (clock != vm_clock || !use_icount) { + return; + } + + /* + * If the CPUs have been sleeping, advance the vm_clock timer now. This + * ensures that the deadline for the timer is computed correctly below. + * This also makes sure that the insn counter is synchronized before the + * CPU starts running, in case the CPU is woken by an event other than + * the earliest vm_clock timer. + */ + icount_warp_rt(NULL); + if (!all_cpu_threads_idle() || !qemu_clock_has_timers(vm_clock)) { + qemu_del_timer(icount_warp_timer); + return; + } + + vm_clock_warp_start = qemu_get_clock_ns(rt_clock); + deadline = qemu_clock_deadline(vm_clock); + if (deadline > 0) { + /* + * Ensure the vm_clock proceeds even when the virtual CPU goes to + * sleep. Otherwise, the CPU might be waiting for a future timer + * interrupt to wake it up, but the interrupt never comes because + * the vCPU isn't running any insns and thus doesn't advance the + * vm_clock. + * + * An extreme solution for this problem would be to never let VCPUs + * sleep in icount mode if there is a pending vm_clock timer; rather + * time could just advance to the next vm_clock event. Instead, we + * do stop VCPUs and only advance vm_clock after some "real" time, + * (related to the time left until the next event) has passed. This + * rt_clock timer will do this. This avoids that the warps are too + * visible externally---for example, you will not be sending network + * packets continously instead of every 100ms. + */ + qemu_mod_timer(icount_warp_timer, vm_clock_warp_start + deadline); + } else { + qemu_notify_event(); + } +} + +static const VMStateDescription vmstate_timers = { + .name = "timer", + .version_id = 2, + .minimum_version_id = 1, + .minimum_version_id_old = 1, + .fields = (VMStateField[]) { + VMSTATE_INT64(cpu_ticks_offset, TimersState), + VMSTATE_INT64(dummy, TimersState), + VMSTATE_INT64_V(cpu_clock_offset, TimersState, 2), + VMSTATE_END_OF_LIST() + } +}; + +void configure_icount(const char *option) +{ + vmstate_register(NULL, 0, &vmstate_timers, &timers_state); + if (!option) { + return; + } + + icount_warp_timer = qemu_new_timer_ns(rt_clock, icount_warp_rt, NULL); + if (strcmp(option, "auto") != 0) { + icount_time_shift = strtol(option, NULL, 0); + use_icount = 1; + return; + } + + use_icount = 2; + + /* 125MIPS seems a reasonable initial guess at the guest speed. + It will be corrected fairly quickly anyway. */ + icount_time_shift = 3; + + /* Have both realtime and virtual time triggers for speed adjustment. + The realtime trigger catches emulated time passing too slowly, + the virtual time trigger catches emulated time passing too fast. + Realtime triggers occur even when idle, so use them less frequently + than VM triggers. */ + icount_rt_timer = qemu_new_timer_ms(rt_clock, icount_adjust_rt, NULL); + qemu_mod_timer(icount_rt_timer, + qemu_get_clock_ms(rt_clock) + 1000); + icount_vm_timer = qemu_new_timer_ns(vm_clock, icount_adjust_vm, NULL); + qemu_mod_timer(icount_vm_timer, + qemu_get_clock_ns(vm_clock) + get_ticks_per_sec() / 10); +} + +/***********************************************************/ void hw_error(const char *fmt, ...) { va_list ap; @@ -686,7 +961,7 @@ static void *qemu_tcg_cpu_thread_fn(void *arg) while (1) { cpu_exec_all(); - if (use_icount && qemu_next_icount_deadline() <= 0) { + if (use_icount && qemu_clock_deadline(vm_clock) <= 0) { qemu_notify_event(); } qemu_tcg_wait_io_event(); @@ -914,7 +1189,7 @@ static int tcg_cpu_exec(CPUState *env) qemu_icount -= (env->icount_decr.u16.low + env->icount_extra); env->icount_decr.u16.low = 0; env->icount_extra = 0; - count = qemu_icount_round(qemu_next_icount_deadline()); + count = qemu_icount_round(qemu_clock_deadline(vm_clock)); qemu_icount += count; decr = (count > 0xffff) ? 0xffff : count; count -= decr; @@ -1006,22 +1281,6 @@ void set_cpu_log_filename(const char *optarg) cpu_set_log_filename(optarg); } -/* Return the virtual CPU time, based on the instruction counter. */ -int64_t cpu_get_icount(void) -{ - int64_t icount; - CPUState *env = cpu_single_env;; - - icount = qemu_icount; - if (env) { - if (!can_do_io(env)) { - fprintf(stderr, "Bad clock read\n"); - } - icount -= (env->icount_decr.u16.low + env->icount_extra); - } - return qemu_icount_bias + (icount << icount_time_shift); -} - void list_cpus(FILE *f, fprintf_function cpu_fprintf, const char *optarg) { /* XXX: implement xxx_cpu_list for targets that still miss it */ |