Reused device migration code for cpu and device state snapshots. In this
initial version, I used several hacks to get the device code working.
vm_stop doesn't have the intended effect (for qemu_save_device_state)
unless called outside the vcpu thread. I trick the function into
thinking it is outside the vcpu thread by temporarily setting
`current_cpu` to be null.
The restore code (qemu_loadvm_state in particular) needs to be called
in a bottom half or a coroutine. I am not sure why.
Signed-off-by: Richard Liu <richy.liu.2...@gmail.com>
---
hw/misc/snapshot.c | 6 ++++
migration/savevm.c | 84 ++++++++++++++++++++++++++++++++++++++++++++++
migration/savevm.h | 3 ++
3 files changed, 93 insertions(+)
diff --git a/hw/misc/snapshot.c b/hw/misc/snapshot.c
index 510bf59dce..afdc5b7f15 100644
--- a/hw/misc/snapshot.c
+++ b/hw/misc/snapshot.c
@@ -55,6 +55,9 @@ static void save_snapshot(struct SnapshotState *s) {
// map as MAP_PRIVATE to avoid carrying writes back to the saved file
fd = open(filepath, O_RDONLY);
mmap(guest_mem, guest_size, PROT_READ | PROT_WRITE, MAP_PRIVATE |
MAP_FIXED, fd, 0);
+
+ // save cpu and device state
+ s->ioc = qemu_snapshot_save_cpu_state();
}
static void restore_snapshot(struct SnapshotState *s) {
@@ -73,6 +76,9 @@ static void restore_snapshot(struct SnapshotState *s) {
fd = open(filepath, O_RDONLY);
mmap(guest_mem, guest_size, PROT_READ | PROT_WRITE, MAP_PRIVATE |
MAP_FIXED, fd, 0);
close(fd);
+
+ // restore cpu and device state
+ qemu_snapshot_load_cpu_state(s->ioc);
}
static uint64_t snapshot_mmio_read(void *opaque, hwaddr addr, unsigned size)
diff --git a/migration/savevm.c b/migration/savevm.c
index 48e85c052c..62e5e5b564 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -3309,3 +3309,87 @@ void qmp_snapshot_delete(const char *job_id,
job_start(&s->common);
}
+
+// saves the cpu and devices state
+QIOChannelBuffer* qemu_snapshot_save_cpu_state(void)
+{
+ QEMUFile *f;
+ QIOChannelBuffer *ioc;
+ MigrationState *ms = migrate_get_current();
+ int ret;
+
+ /* This is a hack to trick vm_stop() into thinking it is not in vcpu
thread.
+ * This is needed to properly stop the VM for a snapshot.
+ */
+ CPUState *cpu = current_cpu;
+ current_cpu = NULL;
+ vm_stop(RUN_STATE_SAVE_VM);
+ current_cpu = cpu;
+
+ global_state_store_running();
+
+ ioc = qio_channel_buffer_new(0x10000);
+ qio_channel_set_name(QIO_CHANNEL(ioc), "snapshot-buffer");
+ f = qemu_file_new_output(QIO_CHANNEL(ioc));
+
+ /* We need to initialize migration otherwise qemu_save_device_state() will
+ * complain.
+ */
+ migrate_init(ms);
+ ms->state = MIGRATION_STATUS_NONE;
+ ms->send_configuration = false;
+
+ cpu_synchronize_all_states();
+
+ ret = qemu_save_device_state(f);
+ if (ret < 0) {
+ fprintf(stderr, "[QEMU] save device err: %d\n", ret);
+ }
+
+ // clean up and restart vm
+ qemu_fflush(f);
+ g_free(f);
+
+ vm_start();
+
+ /* Needed so qemu_loadvm_state does not error with:
+ * qemu-system-x86_64: Expected vmdescription section, but got 0
+ */
+ ms->state = MIGRATION_STATUS_POSTCOPY_ACTIVE;
+
+ return ioc;
+}
+
+// loads the cpu and devices state
+static void do_snapshot_load(void* opaque) {
+ QIOChannelBuffer *ioc = opaque;
+ QEMUFile *f;
+ int ret;
+
+ vm_stop(RUN_STATE_RESTORE_VM);
+
+ // seek back to beginning of file
+ qio_channel_io_seek(QIO_CHANNEL(ioc), 0, 0, NULL);
+ f = qemu_file_new_input(QIO_CHANNEL(ioc));
+
+ ret = qemu_loadvm_state(f);
+ if (ret < 0) {
+ fprintf(stderr, "[QEMU] loadvm err: %d\n", ret);
+ }
+
+ vm_start();
+
+ g_free(f);
+
+ // print time to debug speed
+ struct timespec ts;
+ clock_gettime(CLOCK_MONOTONIC, &ts);
+ fprintf(stderr, "loaded snapshot at %ld.%ld\n", ts.tv_sec, ts.tv_nsec);
+}
+
+void qemu_snapshot_load_cpu_state(QIOChannelBuffer *ioc) {
+ /* Run in a bh because otherwise qemu_loadvm_state won't work
+ */
+ QEMUBH *bh = qemu_bh_new(do_snapshot_load, ioc);
+ qemu_bh_schedule(bh);
+}
diff --git a/migration/savevm.h b/migration/savevm.h
index 6461342cb4..990bcddd2f 100644
--- a/migration/savevm.h
+++ b/migration/savevm.h
@@ -68,4 +68,7 @@ int qemu_load_device_state(QEMUFile *f);
int qemu_savevm_state_complete_precopy_non_iterable(QEMUFile *f,
bool in_postcopy, bool inactivate_disks);
+QIOChannelBuffer* qemu_snapshot_save_cpu_state(void);
+void qemu_snapshot_load_cpu_state(QIOChannelBuffer *ioc);
+
#endif
--
2.35.1
