diff options
Diffstat (limited to 'softmmu/icount.c')
| -rw-r--r-- | softmmu/icount.c | 492 |
1 files changed, 492 insertions, 0 deletions
diff --git a/softmmu/icount.c b/softmmu/icount.c new file mode 100644 index 0000000000..020a201a01 --- /dev/null +++ b/softmmu/icount.c @@ -0,0 +1,492 @@ +/* + * QEMU System Emulator + * + * Copyright (c) 2003-2008 Fabrice Bellard + * + * Permission is hereby granted, free of charge, to any person obtaining a copy + * of this software and associated documentation files (the "Software"), to deal + * in the Software without restriction, including without limitation the rights + * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell + * copies of the Software, and to permit persons to whom the Software is + * furnished to do so, subject to the following conditions: + * + * The above copyright notice and this permission notice shall be included in + * all copies or substantial portions of the Software. + * + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, + * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN + * THE SOFTWARE. + */ + +#include "qemu/osdep.h" +#include "qemu-common.h" +#include "qemu/cutils.h" +#include "migration/vmstate.h" +#include "qapi/error.h" +#include "qemu/error-report.h" +#include "exec/exec-all.h" +#include "sysemu/cpus.h" +#include "sysemu/qtest.h" +#include "qemu/main-loop.h" +#include "qemu/option.h" +#include "qemu/seqlock.h" +#include "sysemu/replay.h" +#include "sysemu/runstate.h" +#include "hw/core/cpu.h" +#include "sysemu/cpu-timers.h" +#include "sysemu/cpu-throttle.h" +#include "timers-state.h" + +/* + * ICOUNT: Instruction Counter + * + * this module is split off from cpu-timers because the icount part + * is TCG-specific, and does not need to be built for other accels. + */ +static bool icount_sleep = true; +/* Arbitrarily pick 1MIPS as the minimum allowable speed. */ +#define MAX_ICOUNT_SHIFT 10 + +/* + * 0 = Do not count executed instructions. + * 1 = Fixed conversion of insn to ns via "shift" option + * 2 = Runtime adaptive algorithm to compute shift + */ +int use_icount; + +static void icount_enable_precise(void) +{ + use_icount = 1; +} + +static void icount_enable_adaptive(void) +{ + use_icount = 2; +} + +/* + * The current number of executed instructions is based on what we + * originally budgeted minus the current state of the decrementing + * icount counters in extra/u16.low. + */ +static int64_t icount_get_executed(CPUState *cpu) +{ + return (cpu->icount_budget - + (cpu_neg(cpu)->icount_decr.u16.low + cpu->icount_extra)); +} + +/* + * Update the global shared timer_state.qemu_icount to take into + * account executed instructions. This is done by the TCG vCPU + * thread so the main-loop can see time has moved forward. + */ +static void icount_update_locked(CPUState *cpu) +{ + int64_t executed = icount_get_executed(cpu); + cpu->icount_budget -= executed; + + qatomic_set_i64(&timers_state.qemu_icount, + timers_state.qemu_icount + executed); +} + +/* + * Update the global shared timer_state.qemu_icount to take into + * account executed instructions. This is done by the TCG vCPU + * thread so the main-loop can see time has moved forward. + */ +void icount_update(CPUState *cpu) +{ + seqlock_write_lock(&timers_state.vm_clock_seqlock, + &timers_state.vm_clock_lock); + icount_update_locked(cpu); + seqlock_write_unlock(&timers_state.vm_clock_seqlock, + &timers_state.vm_clock_lock); +} + +static int64_t icount_get_raw_locked(void) +{ + CPUState *cpu = current_cpu; + + if (cpu && cpu->running) { + if (!cpu->can_do_io) { + error_report("Bad icount read"); + exit(1); + } + /* Take into account what has run */ + icount_update_locked(cpu); + } + /* The read is protected by the seqlock, but needs atomic64 to avoid UB */ + return qatomic_read_i64(&timers_state.qemu_icount); +} + +static int64_t icount_get_locked(void) +{ + int64_t icount = icount_get_raw_locked(); + return qatomic_read_i64(&timers_state.qemu_icount_bias) + + icount_to_ns(icount); +} + +int64_t icount_get_raw(void) +{ + int64_t icount; + unsigned start; + + do { + start = seqlock_read_begin(&timers_state.vm_clock_seqlock); + icount = icount_get_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 icount_get(void) +{ + int64_t icount; + unsigned start; + + do { + start = seqlock_read_begin(&timers_state.vm_clock_seqlock); + icount = icount_get_locked(); + } while (seqlock_read_retry(&timers_state.vm_clock_seqlock, start)); + + return icount; +} + +int64_t icount_to_ns(int64_t icount) +{ + return icount << qatomic_read(&timers_state.icount_time_shift); +} + +/* + * 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 (NANOSECONDS_PER_SECOND / 10) + +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; + } + + seqlock_write_lock(&timers_state.vm_clock_seqlock, + &timers_state.vm_clock_lock); + cur_time = REPLAY_CLOCK_LOCKED(REPLAY_CLOCK_VIRTUAL_RT, + cpu_get_clock_locked()); + cur_icount = icount_get_locked(); + + 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 + && timers_state.icount_time_shift > 0) { + /* The guest is getting too far ahead. Slow time down. */ + qatomic_set(&timers_state.icount_time_shift, + timers_state.icount_time_shift - 1); + } + if (delta < 0 + && last_delta - ICOUNT_WOBBLE > delta * 2 + && timers_state.icount_time_shift < MAX_ICOUNT_SHIFT) { + /* The guest is getting too far behind. Speed time up. */ + qatomic_set(&timers_state.icount_time_shift, + timers_state.icount_time_shift + 1); + } + last_delta = delta; + qatomic_set_i64(&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) +{ + timer_mod(timers_state.icount_rt_timer, + qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL_RT) + 1000); + icount_adjust(); +} + +static void icount_adjust_vm(void *opaque) +{ + timer_mod(timers_state.icount_vm_timer, + qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) + + NANOSECONDS_PER_SECOND / 10); + icount_adjust(); +} + +int64_t icount_round(int64_t count) +{ + int shift = qatomic_read(&timers_state.icount_time_shift); + return (count + (1 << shift) - 1) >> shift; +} + +static void icount_warp_rt(void) +{ + unsigned seq; + int64_t warp_start; + + /* + * The icount_warp_timer is rescheduled soon after vm_clock_warp_start + * changes from -1 to another value, so the race here is okay. + */ + do { + seq = seqlock_read_begin(&timers_state.vm_clock_seqlock); + warp_start = timers_state.vm_clock_warp_start; + } while (seqlock_read_retry(&timers_state.vm_clock_seqlock, seq)); + + if (warp_start == -1) { + return; + } + + seqlock_write_lock(&timers_state.vm_clock_seqlock, + &timers_state.vm_clock_lock); + if (runstate_is_running()) { + int64_t clock = REPLAY_CLOCK_LOCKED(REPLAY_CLOCK_VIRTUAL_RT, + cpu_get_clock_locked()); + int64_t warp_delta; + + warp_delta = clock - timers_state.vm_clock_warp_start; + if (icount_enabled() == 2) { + /* + * In adaptive mode, do not let QEMU_CLOCK_VIRTUAL run too + * far ahead of real time. + */ + int64_t cur_icount = icount_get_locked(); + int64_t delta = clock - cur_icount; + warp_delta = MIN(warp_delta, delta); + } + qatomic_set_i64(&timers_state.qemu_icount_bias, + timers_state.qemu_icount_bias + warp_delta); + } + timers_state.vm_clock_warp_start = -1; + 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); + } +} + +static void icount_timer_cb(void *opaque) +{ + /* + * No need for a checkpoint because the timer already synchronizes + * with CHECKPOINT_CLOCK_VIRTUAL_RT. + */ + icount_warp_rt(); +} + +void icount_start_warp_timer(void) +{ + int64_t clock; + int64_t deadline; + + assert(icount_enabled()); + + /* + * Nothing to do if the VM is stopped: QEMU_CLOCK_VIRTUAL timers + * do not fire, so computing the deadline does not make sense. + */ + if (!runstate_is_running()) { + return; + } + + if (replay_mode != REPLAY_MODE_PLAY) { + if (!all_cpu_threads_idle()) { + return; + } + + if (qtest_enabled()) { + /* When testing, qtest commands advance icount. */ + return; + } + + replay_checkpoint(CHECKPOINT_CLOCK_WARP_START); + } else { + /* warp clock deterministically in record/replay mode */ + if (!replay_checkpoint(CHECKPOINT_CLOCK_WARP_START)) { + /* + * vCPU is sleeping and warp can't be started. + * It is probably a race condition: notification sent + * to vCPU was processed in advance and vCPU went to sleep. + * Therefore we have to wake it up for doing someting. + */ + if (replay_has_checkpoint()) { + qemu_clock_notify(QEMU_CLOCK_VIRTUAL); + } + return; + } + } + + /* We want to use the earliest deadline from ALL vm_clocks */ + clock = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL_RT); + deadline = qemu_clock_deadline_ns_all(QEMU_CLOCK_VIRTUAL, + ~QEMU_TIMER_ATTR_EXTERNAL); + if (deadline < 0) { + static bool notified; + if (!icount_sleep && !notified) { + warn_report("icount sleep disabled and no active timers"); + notified = true; + } + return; + } + + if (deadline > 0) { + /* + * Ensure QEMU_CLOCK_VIRTUAL 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 + * QEMU_CLOCK_VIRTUAL. + */ + if (!icount_sleep) { + /* + * We never let VCPUs sleep in no sleep icount mode. + * If there is a pending QEMU_CLOCK_VIRTUAL timer we just advance + * to the next QEMU_CLOCK_VIRTUAL event and notify it. + * It is useful when we want a deterministic execution time, + * isolated from host latencies. + */ + seqlock_write_lock(&timers_state.vm_clock_seqlock, + &timers_state.vm_clock_lock); + qatomic_set_i64(&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 { + /* + * We do stop VCPUs and only advance QEMU_CLOCK_VIRTUAL after some + * "real" time, (related to the time left until the next event) has + * passed. The QEMU_CLOCK_VIRTUAL_RT clock will do this. + * This avoids that the warps are visible externally; for example, + * you will not be sending network packets continuously instead of + * every 100ms. + */ + 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_unlock(&timers_state.vm_clock_seqlock, + &timers_state.vm_clock_lock); + timer_mod_anticipate(timers_state.icount_warp_timer, + clock + deadline); + } + } else if (deadline == 0) { + qemu_clock_notify(QEMU_CLOCK_VIRTUAL); + } +} + +void icount_account_warp_timer(void) +{ + if (!icount_enabled() || !icount_sleep) { + return; + } + + /* + * Nothing to do if the VM is stopped: QEMU_CLOCK_VIRTUAL timers + * do not fire, so computing the deadline does not make sense. + */ + if (!runstate_is_running()) { + return; + } + + /* warp clock deterministically in record/replay mode */ + if (!replay_checkpoint(CHECKPOINT_CLOCK_WARP_ACCOUNT)) { + return; + } + + timer_del(timers_state.icount_warp_timer); + icount_warp_rt(); +} + +void icount_configure(QemuOpts *opts, Error **errp) +{ + const char *option = qemu_opt_get(opts, "shift"); + bool sleep = qemu_opt_get_bool(opts, "sleep", true); + bool align = qemu_opt_get_bool(opts, "align", false); + long time_shift = -1; + + if (!option) { + if (qemu_opt_get(opts, "align") != NULL) { + error_setg(errp, "Please specify shift option when using align"); + } + return; + } + + if (align && !sleep) { + error_setg(errp, "align=on and sleep=off are incompatible"); + return; + } + + if (strcmp(option, "auto") != 0) { + if (qemu_strtol(option, NULL, 0, &time_shift) < 0 + || time_shift < 0 || time_shift > MAX_ICOUNT_SHIFT) { + error_setg(errp, "icount: Invalid shift value"); + return; + } + } else if (icount_align_option) { + error_setg(errp, "shift=auto and align=on are incompatible"); + return; + } else if (!icount_sleep) { + error_setg(errp, "shift=auto and sleep=off are incompatible"); + return; + } + + icount_sleep = sleep; + if (icount_sleep) { + timers_state.icount_warp_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL_RT, + icount_timer_cb, NULL); + } + + icount_align_option = align; + + if (time_shift >= 0) { + timers_state.icount_time_shift = time_shift; + icount_enable_precise(); + return; + } + + icount_enable_adaptive(); + + /* + * 125MIPS seems a reasonable initial guess at the guest speed. + * It will be corrected fairly quickly anyway. + */ + 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, + * the virtual time trigger catches emulated time passing too fast. + * Realtime triggers occur even when idle, so use them less frequently + * than VM triggers. + */ + timers_state.vm_clock_warp_start = -1; + timers_state.icount_rt_timer = timer_new_ms(QEMU_CLOCK_VIRTUAL_RT, + icount_adjust_rt, NULL); + timer_mod(timers_state.icount_rt_timer, + qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL_RT) + 1000); + timers_state.icount_vm_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL, + icount_adjust_vm, NULL); + timer_mod(timers_state.icount_vm_timer, + qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) + + NANOSECONDS_PER_SECOND / 10); +} |