Peter Xu <pet...@redhat.com> writes:
> On Wed, Mar 06, 2024 at 02:34:25PM +0100, Cédric Le Goater wrote:
>> This prepares ground for the changes coming next which add an Error**
>> argument to the .save_setup() handler. Callers of qemu_savevm_state_setup()
>> now handle the error and fail earlier setting the migration state from
>> MIGRATION_STATUS_SETUP to MIGRATION_STATUS_FAILED.
>>
>> In qemu_savevm_state(), move the cleanup to preserve the error
>> reported by .save_setup() handlers.
>>
>> Since the previous behavior was to ignore errors at this step of
>> migration, this change should be examined closely to check that
>> cleanups are still correctly done.
>>
>> Signed-off-by: Cédric Le Goater <c...@redhat.com>
>> ---
>>
>> Changes in v4:
>>
>> - Merged cleanup change in qemu_savevm_state()
>>
>> Changes in v3:
>>
>> - Set migration state to MIGRATION_STATUS_FAILED
>> - Fixed error handling to be done under lock in bg_migration_thread()
>> - Made sure an error is always set in case of failure in
>> qemu_savevm_state_setup()
>>
>> migration/savevm.h | 2 +-
>> migration/migration.c | 27 ++++++++++++++++++++++++---
>> migration/savevm.c | 26 +++++++++++++++-----------
>> 3 files changed, 40 insertions(+), 15 deletions(-)
>>
>> diff --git a/migration/savevm.h b/migration/savevm.h
>> index
>> 74669733dd63a080b765866c703234a5c4939223..9ec96a995c93a42aad621595f0ed58596c532328
>> 100644
>> --- a/migration/savevm.h
>> +++ b/migration/savevm.h
>> @@ -32,7 +32,7 @@
>> bool qemu_savevm_state_blocked(Error **errp);
>> void qemu_savevm_non_migratable_list(strList **reasons);
>> int qemu_savevm_state_prepare(Error **errp);
>> -void qemu_savevm_state_setup(QEMUFile *f);
>> +int qemu_savevm_state_setup(QEMUFile *f, Error **errp);
>> bool qemu_savevm_state_guest_unplug_pending(void);
>> int qemu_savevm_state_resume_prepare(MigrationState *s);
>> void qemu_savevm_state_header(QEMUFile *f);
>> diff --git a/migration/migration.c b/migration/migration.c
>> index
>> a49fcd53ee19df1ce0182bc99d7e064968f0317b..6d1544224e96f5edfe56939a9c8395d88ef29581
>> 100644
>> --- a/migration/migration.c
>> +++ b/migration/migration.c
>> @@ -3408,6 +3408,8 @@ static void *migration_thread(void *opaque)
>> int64_t setup_start = qemu_clock_get_ms(QEMU_CLOCK_HOST);
>> MigThrError thr_error;
>> bool urgent = false;
>> + Error *local_err = NULL;
>> + int ret;
>>
>> thread = migration_threads_add("live_migration", qemu_get_thread_id());
>>
>> @@ -3451,9 +3453,17 @@ static void *migration_thread(void *opaque)
>> }
>>
>> bql_lock();
>> - qemu_savevm_state_setup(s->to_dst_file);
>> + ret = qemu_savevm_state_setup(s->to_dst_file, &local_err);
>> bql_unlock();
>>
>> + if (ret) {
>> + migrate_set_error(s, local_err);
>> + error_free(local_err);
>> + migrate_set_state(&s->state, MIGRATION_STATUS_SETUP,
>> + MIGRATION_STATUS_FAILED);
>> + goto out;
>> + }
>
> There's a small indent issue, I can fix it.
>
> The bigger problem is I _think_ this will trigger a ci failure in the
> virtio-net-failover test:
>
> ▶ 121/464
> ERROR:../tests/qtest/virtio-net-failover.c:1203:test_migrate_abort_wait_unplug:
> assertion failed (status == "cancelling"): ("cancelled" == "cancelling")
> ERROR
> 121/464 qemu:qtest+qtest-x86_64 / qtest-x86_64/virtio-net-failover ERROR
> 4.77s killed by signal 6 SIGABRT
>>>> PYTHON=/builds/peterx/qemu/build/pyvenv/bin/python3.8
>>>> G_TEST_DBUS_DAEMON=/builds/peterx/qemu/tests/dbus-vmstate-daemon.sh
>>>> MALLOC_PERTURB_=161 QTEST_QEMU_IMG=./qemu-img
>>>> QTEST_QEMU_STORAGE_DAEMON_BINARY=./storage-daemon/qemu-storage-daemon
>>>> QTEST_QEMU_BINARY=./qemu-system-x86_64
>>>> /builds/peterx/qemu/build/tests/qtest/virtio-net-failover --tap -k
> ――――――――――――――――――――――――――――――――――――― ✀ ―――――――――――――――――――――――――――――――――――――
> stderr:
> qemu-system-x86_64: ram_save_setup failed: Input/output error
> **
> ERROR:../tests/qtest/virtio-net-failover.c:1203:test_migrate_abort_wait_unplug:
> assertion failed (status == "cancelling"): ("cancelled" == "cancelling")
I would say testing for the CANCELLING state is unreliable, there's even
code a few lines below in the test that does the proper thing of testing
for CANCELLED in a loop.
However, the comment:
/* while the card is not ejected, we must be in "cancelling" state */
seems to imply that after migrate_fd_cancel (state==CANCELLING), the
migrate_fd_cleanup (state==CANCELLED) would only be executed after
"unplugging the card". So there must be "some logic" that has the effect
of preventing cleanup.
> (test program exited with status code -6)
> ――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――
>
> I am not familiar enough with the failover code, and may not have time
> today to follow this up, copy Laurent. Cedric, if you have time, please
> have a look. I'll give it a shot on Monday to find a solution, otherwise
> we may need to postpone some of the patches to 9.1.
>
> Thanks,
>
>> +
>> qemu_savevm_wait_unplug(s, MIGRATION_STATUS_SETUP,
>> MIGRATION_STATUS_ACTIVE);
>>
>> @@ -3530,6 +3540,9 @@ static void *bg_migration_thread(void *opaque)
>> MigThrError thr_error;
>> QEMUFile *fb;
>> bool early_fail = true;
>> + bool setup_fail = true;
>> + Error *local_err = NULL;
>> + int ret;
>>
>> rcu_register_thread();
>> object_ref(OBJECT(s));
>> @@ -3563,9 +3576,16 @@ static void *bg_migration_thread(void *opaque)
>>
>> bql_lock();
>> qemu_savevm_state_header(s->to_dst_file);
>> - qemu_savevm_state_setup(s->to_dst_file);
>> + ret = qemu_savevm_state_setup(s->to_dst_file, &local_err);
>> + if (ret) {
>> + migrate_set_error(s, local_err);
>> + error_free(local_err);
>> + goto fail;
>> + }
>> bql_unlock();
>>
>> + setup_fail = false;
>> +
>> qemu_savevm_wait_unplug(s, MIGRATION_STATUS_SETUP,
>> MIGRATION_STATUS_ACTIVE);
>>
>> @@ -3632,7 +3652,8 @@ static void *bg_migration_thread(void *opaque)
>>
>> fail:
>> if (early_fail) {
>> - migrate_set_state(&s->state, MIGRATION_STATUS_ACTIVE,
>> + migrate_set_state(&s->state,
>> + setup_fail ? MIGRATION_STATUS_SETUP :
>> MIGRATION_STATUS_ACTIVE,
>> MIGRATION_STATUS_FAILED);
>> bql_unlock();
>> }
>> diff --git a/migration/savevm.c b/migration/savevm.c
>> index
>> ee31ffb5e88cea723039c754c30ce2c8a0ef35f3..63fdbb5ad7d4dbfaef1d2094350bf302cc677602
>> 100644
>> --- a/migration/savevm.c
>> +++ b/migration/savevm.c
>> @@ -1310,11 +1310,11 @@ int qemu_savevm_state_prepare(Error **errp)
>> return 0;
>> }
>>
>> -void qemu_savevm_state_setup(QEMUFile *f)
>> +int qemu_savevm_state_setup(QEMUFile *f, Error **errp)
>> {
>> + ERRP_GUARD();
>> MigrationState *ms = migrate_get_current();
>> SaveStateEntry *se;
>> - Error *local_err = NULL;
>> int ret = 0;
>>
>> json_writer_int64(ms->vmdesc, "page_size", qemu_target_page_size());
>> @@ -1323,10 +1323,9 @@ void qemu_savevm_state_setup(QEMUFile *f)
>> trace_savevm_state_setup();
>> QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {
>> if (se->vmsd && se->vmsd->early_setup) {
>> - ret = vmstate_save(f, se, ms->vmdesc, &local_err);
>> + ret = vmstate_save(f, se, ms->vmdesc, errp);
>> if (ret) {
>> - migrate_set_error(ms, local_err);
>> - error_report_err(local_err);
>> + migrate_set_error(ms, *errp);
>> qemu_file_set_error(f, ret);
>> break;
>> }
>> @@ -1346,18 +1345,19 @@ void qemu_savevm_state_setup(QEMUFile *f)
>> ret = se->ops->save_setup(f, se->opaque);
>> save_section_footer(f, se);
>> if (ret < 0) {
>> + error_setg(errp, "failed to setup SaveStateEntry with id(name):
>> "
>> + "%d(%s): %d", se->section_id, se->idstr, ret);
>> qemu_file_set_error(f, ret);
>> break;
>> }
>> }
>>
>> if (ret) {
>> - return;
>> + return ret;
>> }
>>
>> - if (precopy_notify(PRECOPY_NOTIFY_SETUP, &local_err)) {
>> - error_report_err(local_err);
>> - }
>> + /* TODO: Should we check that errp is set in case of failure ? */
>> + return precopy_notify(PRECOPY_NOTIFY_SETUP, errp);
>> }
>>
>> int qemu_savevm_state_resume_prepare(MigrationState *s)
>> @@ -1728,7 +1728,10 @@ static int qemu_savevm_state(QEMUFile *f, Error
>> **errp)
>> ms->to_dst_file = f;
>>
>> qemu_savevm_state_header(f);
>> - qemu_savevm_state_setup(f);
>> + ret = qemu_savevm_state_setup(f, errp);
>> + if (ret) {
>> + goto cleanup;
>> + }
>>
>> while (qemu_file_get_error(f) == 0) {
>> if (qemu_savevm_state_iterate(f, false) > 0) {
>> @@ -1741,10 +1744,11 @@ static int qemu_savevm_state(QEMUFile *f, Error
>> **errp)
>> qemu_savevm_state_complete_precopy(f, false, false);
>> ret = qemu_file_get_error(f);
>> }
>> - qemu_savevm_state_cleanup();
>> if (ret != 0) {
>> error_setg_errno(errp, -ret, "Error while writing VM state");
>> }
>> +cleanup:
>> + qemu_savevm_state_cleanup();
>>
>> if (ret != 0) {
>> status = MIGRATION_STATUS_FAILED;
>> --
>> 2.44.0
>>
