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![Marc-André Lureau](/assets/img/avatar_default.png)
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com> Message-Id: <20220323155743.1585078-33-marcandre.lureau@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
489 lines
16 KiB
C
489 lines
16 KiB
C
/*
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* QEMU System Emulator
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*
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* Copyright (c) 2003-2008 Fabrice Bellard
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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#include "qemu/osdep.h"
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#include "qemu/cutils.h"
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#include "migration/vmstate.h"
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#include "qapi/error.h"
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#include "qemu/error-report.h"
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#include "exec/exec-all.h"
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#include "sysemu/cpus.h"
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#include "sysemu/qtest.h"
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#include "qemu/main-loop.h"
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#include "qemu/option.h"
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#include "qemu/seqlock.h"
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#include "sysemu/replay.h"
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#include "sysemu/runstate.h"
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#include "hw/core/cpu.h"
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#include "sysemu/cpu-timers.h"
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#include "sysemu/cpu-throttle.h"
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#include "timers-state.h"
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/*
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* ICOUNT: Instruction Counter
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*
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* this module is split off from cpu-timers because the icount part
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* is TCG-specific, and does not need to be built for other accels.
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*/
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static bool icount_sleep = true;
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/* Arbitrarily pick 1MIPS as the minimum allowable speed. */
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#define MAX_ICOUNT_SHIFT 10
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/*
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* 0 = Do not count executed instructions.
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* 1 = Fixed conversion of insn to ns via "shift" option
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* 2 = Runtime adaptive algorithm to compute shift
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*/
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int use_icount;
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static void icount_enable_precise(void)
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{
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use_icount = 1;
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}
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static void icount_enable_adaptive(void)
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{
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use_icount = 2;
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}
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/*
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* The current number of executed instructions is based on what we
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* originally budgeted minus the current state of the decrementing
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* icount counters in extra/u16.low.
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*/
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static int64_t icount_get_executed(CPUState *cpu)
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{
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return (cpu->icount_budget -
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(cpu_neg(cpu)->icount_decr.u16.low + cpu->icount_extra));
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}
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/*
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* Update the global shared timer_state.qemu_icount to take into
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* account executed instructions. This is done by the TCG vCPU
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* thread so the main-loop can see time has moved forward.
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*/
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static void icount_update_locked(CPUState *cpu)
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{
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int64_t executed = icount_get_executed(cpu);
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cpu->icount_budget -= executed;
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qatomic_set_i64(&timers_state.qemu_icount,
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timers_state.qemu_icount + executed);
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}
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/*
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* Update the global shared timer_state.qemu_icount to take into
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* account executed instructions. This is done by the TCG vCPU
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* thread so the main-loop can see time has moved forward.
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*/
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void icount_update(CPUState *cpu)
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{
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seqlock_write_lock(&timers_state.vm_clock_seqlock,
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&timers_state.vm_clock_lock);
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icount_update_locked(cpu);
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seqlock_write_unlock(&timers_state.vm_clock_seqlock,
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&timers_state.vm_clock_lock);
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}
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static int64_t icount_get_raw_locked(void)
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{
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CPUState *cpu = current_cpu;
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if (cpu && cpu->running) {
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if (!cpu->can_do_io) {
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error_report("Bad icount read");
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exit(1);
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}
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/* Take into account what has run */
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icount_update_locked(cpu);
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}
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/* The read is protected by the seqlock, but needs atomic64 to avoid UB */
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return qatomic_read_i64(&timers_state.qemu_icount);
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}
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static int64_t icount_get_locked(void)
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{
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int64_t icount = icount_get_raw_locked();
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return qatomic_read_i64(&timers_state.qemu_icount_bias) +
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icount_to_ns(icount);
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}
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int64_t icount_get_raw(void)
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{
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int64_t icount;
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unsigned start;
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do {
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start = seqlock_read_begin(&timers_state.vm_clock_seqlock);
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icount = icount_get_raw_locked();
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} while (seqlock_read_retry(&timers_state.vm_clock_seqlock, start));
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return icount;
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}
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/* Return the virtual CPU time, based on the instruction counter. */
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int64_t icount_get(void)
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{
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int64_t icount;
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unsigned start;
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do {
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start = seqlock_read_begin(&timers_state.vm_clock_seqlock);
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icount = icount_get_locked();
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} while (seqlock_read_retry(&timers_state.vm_clock_seqlock, start));
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return icount;
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}
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int64_t icount_to_ns(int64_t icount)
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{
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return icount << qatomic_read(&timers_state.icount_time_shift);
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}
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/*
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* Correlation between real and virtual time is always going to be
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* fairly approximate, so ignore small variation.
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* When the guest is idle real and virtual time will be aligned in
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* the IO wait loop.
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*/
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#define ICOUNT_WOBBLE (NANOSECONDS_PER_SECOND / 10)
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static void icount_adjust(void)
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{
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int64_t cur_time;
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int64_t cur_icount;
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int64_t delta;
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/* If the VM is not running, then do nothing. */
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if (!runstate_is_running()) {
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return;
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}
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seqlock_write_lock(&timers_state.vm_clock_seqlock,
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&timers_state.vm_clock_lock);
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cur_time = REPLAY_CLOCK_LOCKED(REPLAY_CLOCK_VIRTUAL_RT,
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cpu_get_clock_locked());
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cur_icount = icount_get_locked();
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delta = cur_icount - cur_time;
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/* FIXME: This is a very crude algorithm, somewhat prone to oscillation. */
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if (delta > 0
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&& timers_state.last_delta + ICOUNT_WOBBLE < delta * 2
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&& timers_state.icount_time_shift > 0) {
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/* The guest is getting too far ahead. Slow time down. */
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qatomic_set(&timers_state.icount_time_shift,
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timers_state.icount_time_shift - 1);
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}
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if (delta < 0
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&& timers_state.last_delta - ICOUNT_WOBBLE > delta * 2
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&& timers_state.icount_time_shift < MAX_ICOUNT_SHIFT) {
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/* The guest is getting too far behind. Speed time up. */
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qatomic_set(&timers_state.icount_time_shift,
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timers_state.icount_time_shift + 1);
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}
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timers_state.last_delta = delta;
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qatomic_set_i64(&timers_state.qemu_icount_bias,
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cur_icount - (timers_state.qemu_icount
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<< timers_state.icount_time_shift));
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seqlock_write_unlock(&timers_state.vm_clock_seqlock,
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&timers_state.vm_clock_lock);
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}
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static void icount_adjust_rt(void *opaque)
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{
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timer_mod(timers_state.icount_rt_timer,
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qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL_RT) + 1000);
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icount_adjust();
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}
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static void icount_adjust_vm(void *opaque)
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{
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timer_mod(timers_state.icount_vm_timer,
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qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) +
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NANOSECONDS_PER_SECOND / 10);
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icount_adjust();
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}
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int64_t icount_round(int64_t count)
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{
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int shift = qatomic_read(&timers_state.icount_time_shift);
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return (count + (1 << shift) - 1) >> shift;
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}
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static void icount_warp_rt(void)
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{
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unsigned seq;
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int64_t warp_start;
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/*
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* The icount_warp_timer is rescheduled soon after vm_clock_warp_start
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* changes from -1 to another value, so the race here is okay.
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*/
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do {
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seq = seqlock_read_begin(&timers_state.vm_clock_seqlock);
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warp_start = timers_state.vm_clock_warp_start;
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} while (seqlock_read_retry(&timers_state.vm_clock_seqlock, seq));
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if (warp_start == -1) {
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return;
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}
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seqlock_write_lock(&timers_state.vm_clock_seqlock,
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&timers_state.vm_clock_lock);
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if (runstate_is_running()) {
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int64_t clock = REPLAY_CLOCK_LOCKED(REPLAY_CLOCK_VIRTUAL_RT,
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cpu_get_clock_locked());
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int64_t warp_delta;
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warp_delta = clock - timers_state.vm_clock_warp_start;
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if (icount_enabled() == 2) {
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/*
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* In adaptive mode, do not let QEMU_CLOCK_VIRTUAL run too
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* far ahead of real time.
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*/
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int64_t cur_icount = icount_get_locked();
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int64_t delta = clock - cur_icount;
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warp_delta = MIN(warp_delta, delta);
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}
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qatomic_set_i64(&timers_state.qemu_icount_bias,
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timers_state.qemu_icount_bias + warp_delta);
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}
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timers_state.vm_clock_warp_start = -1;
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seqlock_write_unlock(&timers_state.vm_clock_seqlock,
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&timers_state.vm_clock_lock);
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if (qemu_clock_expired(QEMU_CLOCK_VIRTUAL)) {
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qemu_clock_notify(QEMU_CLOCK_VIRTUAL);
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}
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}
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static void icount_timer_cb(void *opaque)
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{
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/*
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* No need for a checkpoint because the timer already synchronizes
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* with CHECKPOINT_CLOCK_VIRTUAL_RT.
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*/
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icount_warp_rt();
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}
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void icount_start_warp_timer(void)
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{
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int64_t clock;
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int64_t deadline;
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assert(icount_enabled());
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/*
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* Nothing to do if the VM is stopped: QEMU_CLOCK_VIRTUAL timers
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* do not fire, so computing the deadline does not make sense.
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*/
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if (!runstate_is_running()) {
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return;
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}
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if (replay_mode != REPLAY_MODE_PLAY) {
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if (!all_cpu_threads_idle()) {
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return;
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}
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if (qtest_enabled()) {
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/* When testing, qtest commands advance icount. */
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return;
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}
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replay_checkpoint(CHECKPOINT_CLOCK_WARP_START);
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} else {
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/* warp clock deterministically in record/replay mode */
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if (!replay_checkpoint(CHECKPOINT_CLOCK_WARP_START)) {
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/*
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* vCPU is sleeping and warp can't be started.
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* It is probably a race condition: notification sent
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* to vCPU was processed in advance and vCPU went to sleep.
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* Therefore we have to wake it up for doing someting.
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*/
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if (replay_has_checkpoint()) {
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qemu_clock_notify(QEMU_CLOCK_VIRTUAL);
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}
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return;
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}
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}
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/* We want to use the earliest deadline from ALL vm_clocks */
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clock = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL_RT);
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deadline = qemu_clock_deadline_ns_all(QEMU_CLOCK_VIRTUAL,
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~QEMU_TIMER_ATTR_EXTERNAL);
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if (deadline < 0) {
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static bool notified;
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if (!icount_sleep && !notified) {
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warn_report("icount sleep disabled and no active timers");
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notified = true;
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}
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return;
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}
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if (deadline > 0) {
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/*
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* Ensure QEMU_CLOCK_VIRTUAL proceeds even when the virtual CPU goes to
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* sleep. Otherwise, the CPU might be waiting for a future timer
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* interrupt to wake it up, but the interrupt never comes because
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* the vCPU isn't running any insns and thus doesn't advance the
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* QEMU_CLOCK_VIRTUAL.
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*/
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if (!icount_sleep) {
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/*
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* We never let VCPUs sleep in no sleep icount mode.
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* If there is a pending QEMU_CLOCK_VIRTUAL timer we just advance
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* to the next QEMU_CLOCK_VIRTUAL event and notify it.
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* It is useful when we want a deterministic execution time,
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* isolated from host latencies.
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*/
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seqlock_write_lock(&timers_state.vm_clock_seqlock,
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&timers_state.vm_clock_lock);
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qatomic_set_i64(&timers_state.qemu_icount_bias,
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timers_state.qemu_icount_bias + deadline);
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seqlock_write_unlock(&timers_state.vm_clock_seqlock,
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&timers_state.vm_clock_lock);
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qemu_clock_notify(QEMU_CLOCK_VIRTUAL);
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} else {
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/*
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* We do stop VCPUs and only advance QEMU_CLOCK_VIRTUAL after some
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* "real" time, (related to the time left until the next event) has
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* passed. The QEMU_CLOCK_VIRTUAL_RT clock will do this.
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* This avoids that the warps are visible externally; for example,
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* you will not be sending network packets continuously instead of
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* every 100ms.
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*/
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seqlock_write_lock(&timers_state.vm_clock_seqlock,
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&timers_state.vm_clock_lock);
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if (timers_state.vm_clock_warp_start == -1
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|| timers_state.vm_clock_warp_start > clock) {
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timers_state.vm_clock_warp_start = clock;
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}
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seqlock_write_unlock(&timers_state.vm_clock_seqlock,
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&timers_state.vm_clock_lock);
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timer_mod_anticipate(timers_state.icount_warp_timer,
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clock + deadline);
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}
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} else if (deadline == 0) {
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qemu_clock_notify(QEMU_CLOCK_VIRTUAL);
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}
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}
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void icount_account_warp_timer(void)
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{
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if (!icount_sleep) {
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return;
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}
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/*
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* Nothing to do if the VM is stopped: QEMU_CLOCK_VIRTUAL timers
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* do not fire, so computing the deadline does not make sense.
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*/
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if (!runstate_is_running()) {
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return;
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}
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/* warp clock deterministically in record/replay mode */
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if (!replay_checkpoint(CHECKPOINT_CLOCK_WARP_ACCOUNT)) {
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return;
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}
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timer_del(timers_state.icount_warp_timer);
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icount_warp_rt();
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}
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void icount_configure(QemuOpts *opts, Error **errp)
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{
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const char *option = qemu_opt_get(opts, "shift");
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bool sleep = qemu_opt_get_bool(opts, "sleep", true);
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bool align = qemu_opt_get_bool(opts, "align", false);
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long time_shift = -1;
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if (!option) {
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if (qemu_opt_get(opts, "align") != NULL) {
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error_setg(errp, "Please specify shift option when using align");
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}
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return;
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}
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if (align && !sleep) {
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error_setg(errp, "align=on and sleep=off are incompatible");
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return;
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}
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if (strcmp(option, "auto") != 0) {
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if (qemu_strtol(option, NULL, 0, &time_shift) < 0
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|| time_shift < 0 || time_shift > MAX_ICOUNT_SHIFT) {
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error_setg(errp, "icount: Invalid shift value");
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return;
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}
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} else if (icount_align_option) {
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error_setg(errp, "shift=auto and align=on are incompatible");
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return;
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} else if (!icount_sleep) {
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error_setg(errp, "shift=auto and sleep=off are incompatible");
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return;
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}
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icount_sleep = sleep;
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if (icount_sleep) {
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timers_state.icount_warp_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL_RT,
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icount_timer_cb, NULL);
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}
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icount_align_option = align;
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if (time_shift >= 0) {
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timers_state.icount_time_shift = time_shift;
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icount_enable_precise();
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return;
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}
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icount_enable_adaptive();
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/*
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* 125MIPS seems a reasonable initial guess at the guest speed.
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* It will be corrected fairly quickly anyway.
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*/
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timers_state.icount_time_shift = 3;
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/*
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* Have both realtime and virtual time triggers for speed adjustment.
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* The realtime trigger catches emulated time passing too slowly,
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* the virtual time trigger catches emulated time passing too fast.
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* Realtime triggers occur even when idle, so use them less frequently
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* than VM triggers.
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*/
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timers_state.vm_clock_warp_start = -1;
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timers_state.icount_rt_timer = timer_new_ms(QEMU_CLOCK_VIRTUAL_RT,
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icount_adjust_rt, NULL);
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timer_mod(timers_state.icount_rt_timer,
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qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL_RT) + 1000);
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timers_state.icount_vm_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL,
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icount_adjust_vm, NULL);
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timer_mod(timers_state.icount_vm_timer,
|
|
qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) +
|
|
NANOSECONDS_PER_SECOND / 10);
|
|
}
|