/*
* 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;
/* 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
&& timers_state.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
&& timers_state.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);
}
timers_state.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_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);
}
