qemu/replay/replay.c
Pavel Dovgalyuk 0c08185f8f replay: wake up vCPU when replaying
In record/replay icount mode vCPU thread and iothread synchronize
the execution using the checkpoints.
vCPU thread processes the virtual timers and iothread processes all others.
When iothread wants to wake up sleeping vCPU thread, it sends dummy queued
work. Therefore it could be the following sequence of the events in
record mode:
 - IO: sending dummy work
 - IO: processing timers
 - CPU: wakeup
 - CPU: clearing dummy work
 - CPU: processing virtual timers

But due to the races in replay mode the sequence may change:
 - IO: sending dummy work
 - CPU: wakeup
 - CPU: clearing dummy work
 - CPU: sleeping again because nothing to do
 - IO: Processing timers
 - CPU: zzzz

In this case vCPU will not wake up, because dummy work is not to be set up
again.

This patch tries to wake up the vCPU when it sleeps and the icount warp
checkpoint isn't met. It means that vCPU has something to do, because
there are no other reasons of non-matching warp checkpoint.

Signed-off-by: Pavel Dovgalyuk <Pavel.Dovgaluk@ispras.ru>

--

v5: improve checking that vCPU is still sleeping
Message-Id: <20180912081945.3228.19776.stgit@pasha-VirtualBox>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2018-10-02 19:08:51 +02:00

388 lines
9.8 KiB
C

/*
* replay.c
*
* Copyright (c) 2010-2015 Institute for System Programming
* of the Russian Academy of Sciences.
*
* This work is licensed under the terms of the GNU GPL, version 2 or later.
* See the COPYING file in the top-level directory.
*
*/
#include "qemu/osdep.h"
#include "qapi/error.h"
#include "sysemu/replay.h"
#include "replay-internal.h"
#include "qemu/timer.h"
#include "qemu/main-loop.h"
#include "qemu/option.h"
#include "sysemu/cpus.h"
#include "sysemu/sysemu.h"
#include "qemu/error-report.h"
/* Current version of the replay mechanism.
Increase it when file format changes. */
#define REPLAY_VERSION 0xe02007
/* Size of replay log header */
#define HEADER_SIZE (sizeof(uint32_t) + sizeof(uint64_t))
ReplayMode replay_mode = REPLAY_MODE_NONE;
char *replay_snapshot;
/* Name of replay file */
static char *replay_filename;
ReplayState replay_state;
static GSList *replay_blockers;
bool replay_next_event_is(int event)
{
bool res = false;
/* nothing to skip - not all instructions used */
if (replay_state.instructions_count != 0) {
assert(replay_state.data_kind == EVENT_INSTRUCTION);
return event == EVENT_INSTRUCTION;
}
while (true) {
if (event == replay_state.data_kind) {
res = true;
}
switch (replay_state.data_kind) {
case EVENT_SHUTDOWN ... EVENT_SHUTDOWN_LAST:
replay_finish_event();
qemu_system_shutdown_request(replay_state.data_kind -
EVENT_SHUTDOWN);
break;
default:
/* clock, time_t, checkpoint and other events */
return res;
}
}
return res;
}
uint64_t replay_get_current_step(void)
{
return cpu_get_icount_raw();
}
int replay_get_instructions(void)
{
int res = 0;
replay_mutex_lock();
if (replay_next_event_is(EVENT_INSTRUCTION)) {
res = replay_state.instructions_count;
}
replay_mutex_unlock();
return res;
}
void replay_account_executed_instructions(void)
{
if (replay_mode == REPLAY_MODE_PLAY) {
g_assert(replay_mutex_locked());
if (replay_state.instructions_count > 0) {
int count = (int)(replay_get_current_step()
- replay_state.current_step);
/* Time can only go forward */
assert(count >= 0);
replay_state.instructions_count -= count;
replay_state.current_step += count;
if (replay_state.instructions_count == 0) {
assert(replay_state.data_kind == EVENT_INSTRUCTION);
replay_finish_event();
/* Wake up iothread. This is required because
timers will not expire until clock counters
will be read from the log. */
qemu_notify_event();
}
}
}
}
bool replay_exception(void)
{
if (replay_mode == REPLAY_MODE_RECORD) {
g_assert(replay_mutex_locked());
replay_save_instructions();
replay_put_event(EVENT_EXCEPTION);
return true;
} else if (replay_mode == REPLAY_MODE_PLAY) {
g_assert(replay_mutex_locked());
bool res = replay_has_exception();
if (res) {
replay_finish_event();
}
return res;
}
return true;
}
bool replay_has_exception(void)
{
bool res = false;
if (replay_mode == REPLAY_MODE_PLAY) {
g_assert(replay_mutex_locked());
replay_account_executed_instructions();
res = replay_next_event_is(EVENT_EXCEPTION);
}
return res;
}
bool replay_interrupt(void)
{
if (replay_mode == REPLAY_MODE_RECORD) {
g_assert(replay_mutex_locked());
replay_save_instructions();
replay_put_event(EVENT_INTERRUPT);
return true;
} else if (replay_mode == REPLAY_MODE_PLAY) {
g_assert(replay_mutex_locked());
bool res = replay_has_interrupt();
if (res) {
replay_finish_event();
}
return res;
}
return true;
}
bool replay_has_interrupt(void)
{
bool res = false;
if (replay_mode == REPLAY_MODE_PLAY) {
g_assert(replay_mutex_locked());
replay_account_executed_instructions();
res = replay_next_event_is(EVENT_INTERRUPT);
}
return res;
}
void replay_shutdown_request(ShutdownCause cause)
{
if (replay_mode == REPLAY_MODE_RECORD) {
g_assert(replay_mutex_locked());
replay_put_event(EVENT_SHUTDOWN + cause);
}
}
bool replay_checkpoint(ReplayCheckpoint checkpoint)
{
bool res = false;
static bool in_checkpoint;
assert(EVENT_CHECKPOINT + checkpoint <= EVENT_CHECKPOINT_LAST);
if (!replay_file) {
return true;
}
if (in_checkpoint) {
/* If we are already in checkpoint, then there is no need
for additional synchronization.
Recursion occurs when HW event modifies timers.
Timer modification may invoke the checkpoint and
proceed to recursion. */
return true;
}
in_checkpoint = true;
replay_save_instructions();
if (replay_mode == REPLAY_MODE_PLAY) {
g_assert(replay_mutex_locked());
if (replay_next_event_is(EVENT_CHECKPOINT + checkpoint)) {
replay_finish_event();
} else if (replay_state.data_kind != EVENT_ASYNC) {
res = false;
goto out;
}
replay_read_events(checkpoint);
/* replay_read_events may leave some unread events.
Return false if not all of the events associated with
checkpoint were processed */
res = replay_state.data_kind != EVENT_ASYNC;
} else if (replay_mode == REPLAY_MODE_RECORD) {
g_assert(replay_mutex_locked());
replay_put_event(EVENT_CHECKPOINT + checkpoint);
/* This checkpoint belongs to several threads.
Processing events from different threads is
non-deterministic */
if (checkpoint != CHECKPOINT_CLOCK_WARP_START) {
replay_save_events(checkpoint);
}
res = true;
}
out:
in_checkpoint = false;
return res;
}
bool replay_has_checkpoint(void)
{
bool res = false;
if (replay_mode == REPLAY_MODE_PLAY) {
g_assert(replay_mutex_locked());
replay_account_executed_instructions();
res = EVENT_CHECKPOINT <= replay_state.data_kind
&& replay_state.data_kind <= EVENT_CHECKPOINT_LAST;
}
return res;
}
static void replay_enable(const char *fname, int mode)
{
const char *fmode = NULL;
assert(!replay_file);
switch (mode) {
case REPLAY_MODE_RECORD:
fmode = "wb";
break;
case REPLAY_MODE_PLAY:
fmode = "rb";
break;
default:
fprintf(stderr, "Replay: internal error: invalid replay mode\n");
exit(1);
}
atexit(replay_finish);
replay_file = fopen(fname, fmode);
if (replay_file == NULL) {
fprintf(stderr, "Replay: open %s: %s\n", fname, strerror(errno));
exit(1);
}
replay_filename = g_strdup(fname);
replay_mode = mode;
replay_mutex_init();
replay_state.data_kind = -1;
replay_state.instructions_count = 0;
replay_state.current_step = 0;
replay_state.has_unread_data = 0;
/* skip file header for RECORD and check it for PLAY */
if (replay_mode == REPLAY_MODE_RECORD) {
fseek(replay_file, HEADER_SIZE, SEEK_SET);
} else if (replay_mode == REPLAY_MODE_PLAY) {
unsigned int version = replay_get_dword();
if (version != REPLAY_VERSION) {
fprintf(stderr, "Replay: invalid input log file version\n");
exit(1);
}
/* go to the beginning */
fseek(replay_file, HEADER_SIZE, SEEK_SET);
replay_fetch_data_kind();
}
replay_init_events();
}
void replay_configure(QemuOpts *opts)
{
const char *fname;
const char *rr;
ReplayMode mode = REPLAY_MODE_NONE;
Location loc;
if (!opts) {
return;
}
loc_push_none(&loc);
qemu_opts_loc_restore(opts);
rr = qemu_opt_get(opts, "rr");
if (!rr) {
/* Just enabling icount */
goto out;
} else if (!strcmp(rr, "record")) {
mode = REPLAY_MODE_RECORD;
} else if (!strcmp(rr, "replay")) {
mode = REPLAY_MODE_PLAY;
} else {
error_report("Invalid icount rr option: %s", rr);
exit(1);
}
fname = qemu_opt_get(opts, "rrfile");
if (!fname) {
error_report("File name not specified for replay");
exit(1);
}
replay_snapshot = g_strdup(qemu_opt_get(opts, "rrsnapshot"));
replay_vmstate_register();
replay_enable(fname, mode);
out:
loc_pop(&loc);
}
void replay_start(void)
{
if (replay_mode == REPLAY_MODE_NONE) {
return;
}
if (replay_blockers) {
error_reportf_err(replay_blockers->data, "Record/replay: ");
exit(1);
}
if (!use_icount) {
error_report("Please enable icount to use record/replay");
exit(1);
}
/* Timer for snapshotting will be set up here. */
replay_enable_events();
}
void replay_finish(void)
{
if (replay_mode == REPLAY_MODE_NONE) {
return;
}
replay_save_instructions();
/* finalize the file */
if (replay_file) {
if (replay_mode == REPLAY_MODE_RECORD) {
/* write end event */
replay_put_event(EVENT_END);
/* write header */
fseek(replay_file, 0, SEEK_SET);
replay_put_dword(REPLAY_VERSION);
}
fclose(replay_file);
replay_file = NULL;
}
if (replay_filename) {
g_free(replay_filename);
replay_filename = NULL;
}
g_free(replay_snapshot);
replay_snapshot = NULL;
replay_finish_events();
}
void replay_add_blocker(Error *reason)
{
replay_blockers = g_slist_prepend(replay_blockers, reason);
}