On Fri, Oct 11, 2019 at 01:20:12PM +0200, Jens Freimann wrote:
> This patch adds a new migration state called wait-unplug. It is entered
> after the SETUP state and will transition into ACTIVE once all devices
> were succesfully unplugged from the guest.
>
> So if a guest doesn't respond or takes long to honor the unplug request
> the user will see the migration state 'wait-unplug'.
>
> In the migration thread we query failover devices if they're are still
> pending the guest unplug. When all are unplugged the migration
> continues. We give it a defined number of iterations including small
> waiting periods before we proceed.
>
> Signed-off-by: Jens Freimann <jfreim...@redhat.com>
> ---
> include/migration/vmstate.h | 2 ++
> migration/migration.c | 34 ++++++++++++++++++++++++++++++++++
> migration/migration.h | 3 +++
> migration/savevm.c | 36 ++++++++++++++++++++++++++++++++++++
> migration/savevm.h | 1 +
> qapi/migration.json | 5 ++++-
> 6 files changed, 80 insertions(+), 1 deletion(-)
>
> diff --git a/include/migration/vmstate.h b/include/migration/vmstate.h
> index 1fbfd099dd..39ef125225 100644
> --- a/include/migration/vmstate.h
> +++ b/include/migration/vmstate.h
> @@ -186,6 +186,8 @@ struct VMStateDescription {
> int (*pre_save)(void *opaque);
> int (*post_save)(void *opaque);
> bool (*needed)(void *opaque);
> + bool (*dev_unplug_pending)(void *opaque);
> +
> const VMStateField *fields;
> const VMStateDescription **subsections;
> };
> diff --git a/migration/migration.c b/migration/migration.c
> index 5f7e4d15e9..a17d9fb990 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -52,9 +52,14 @@
> #include "hw/qdev-properties.h"
> #include "monitor/monitor.h"
> #include "net/announce.h"
> +#include "qemu/queue.h"
>
> #define MAX_THROTTLE (32 << 20) /* Migration transfer speed throttling
> */
>
> +/* Time in milliseconds to wait for guest OS to unplug PCI device */
> +#define FAILOVER_GUEST_UNPLUG_WAIT 10000
This value should be controllable from QMP.
And I think the default should be infinite wait.
> +#define FAILOVER_UNPLUG_RETRIES 5
This is a bit of a hack. We really should just
have unplug signal wakeup, or time expire.
E.g. a new kind of notifier?
> +
> /* Amount of time to allocate to each "chunk" of bandwidth-throttled
> * data. */
> #define BUFFER_DELAY 100
> @@ -954,6 +959,9 @@ static void fill_source_migration_info(MigrationInfo
> *info)
> case MIGRATION_STATUS_CANCELLED:
> info->has_status = true;
> break;
> + case MIGRATION_STATUS_WAIT_UNPLUG:
> + info->has_status = true;
> + break;
> }
> info->status = s->state;
> }
> @@ -1695,6 +1703,7 @@ bool migration_is_idle(void)
> case MIGRATION_STATUS_COLO:
> case MIGRATION_STATUS_PRE_SWITCHOVER:
> case MIGRATION_STATUS_DEVICE:
> + case MIGRATION_STATUS_WAIT_UNPLUG:
> return false;
> case MIGRATION_STATUS__MAX:
> g_assert_not_reached();
> @@ -3224,6 +3233,8 @@ static void *migration_thread(void *opaque)
> int64_t setup_start = qemu_clock_get_ms(QEMU_CLOCK_HOST);
> MigThrError thr_error;
> bool urgent = false;
> + bool all_unplugged = true;
> + int i = 0;
>
> rcu_register_thread();
>
> @@ -3260,6 +3271,27 @@ static void *migration_thread(void *opaque)
>
> qemu_savevm_state_setup(s->to_dst_file);
>
> + migrate_set_state(&s->state, MIGRATION_STATUS_SETUP,
> + MIGRATION_STATUS_WAIT_UNPLUG);
> +
> + while (i < FAILOVER_UNPLUG_RETRIES &&
> + s->state == MIGRATION_STATUS_WAIT_UNPLUG) {
> + i++;
> + qemu_sem_timedwait(&s->wait_unplug_sem, FAILOVER_GUEST_UNPLUG_WAIT);
Should be FAILOVER_GUEST_UNPLUG_WAIT / FAILOVER_UNPLUG_RETRIES
such that time set is the total.
> + all_unplugged = qemu_savevm_state_guest_unplug_pending();
> + if (all_unplugged) {
> + break;
> + }
> + }
> +
> + if (all_unplugged) {
> + migrate_set_state(&s->state, MIGRATION_STATUS_WAIT_UNPLUG,
> + MIGRATION_STATUS_ACTIVE);
> + } else {
> + migrate_set_state(&s->state, MIGRATION_STATUS_WAIT_UNPLUG,
> + MIGRATION_STATUS_CANCELLING);
> + }
> +
> s->setup_time = qemu_clock_get_ms(QEMU_CLOCK_HOST) - setup_start;
> migrate_set_state(&s->state, MIGRATION_STATUS_SETUP,
> MIGRATION_STATUS_ACTIVE);
> @@ -3508,6 +3540,7 @@ static void migration_instance_finalize(Object *obj)
> qemu_mutex_destroy(&ms->qemu_file_lock);
> g_free(params->tls_hostname);
> g_free(params->tls_creds);
> + qemu_sem_destroy(&ms->wait_unplug_sem);
> qemu_sem_destroy(&ms->rate_limit_sem);
> qemu_sem_destroy(&ms->pause_sem);
> qemu_sem_destroy(&ms->postcopy_pause_sem);
> @@ -3553,6 +3586,7 @@ static void migration_instance_init(Object *obj)
> qemu_sem_init(&ms->postcopy_pause_rp_sem, 0);
> qemu_sem_init(&ms->rp_state.rp_sem, 0);
> qemu_sem_init(&ms->rate_limit_sem, 0);
> + qemu_sem_init(&ms->wait_unplug_sem, 0);
> qemu_mutex_init(&ms->qemu_file_lock);
> }
>
> diff --git a/migration/migration.h b/migration/migration.h
> index 4f2fe193dc..79b3dda146 100644
> --- a/migration/migration.h
> +++ b/migration/migration.h
> @@ -206,6 +206,9 @@ struct MigrationState
> /* Flag set once the migration thread called bdrv_inactivate_all */
> bool block_inactive;
>
> + /* Migration is waiting for guest to unplug device */
> + QemuSemaphore wait_unplug_sem;
> +
> /* Migration is paused due to pause-before-switchover */
> QemuSemaphore pause_sem;
>
> diff --git a/migration/savevm.c b/migration/savevm.c
> index bb9462a54d..26e5bde687 100644
> --- a/migration/savevm.c
> +++ b/migration/savevm.c
> @@ -942,6 +942,20 @@ static void qemu_savevm_command_send(QEMUFile *f,
> qemu_fflush(f);
> }
>
> +static int qemu_savevm_nr_failover_devices(void)
> +{
> + SaveStateEntry *se;
> + int n = 0;
> +
> + QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {
> + if (se->vmsd && se->vmsd->dev_unplug_pending) {
> + n++;
> + }
> + }
> +
> + return n;
> +}
> +
> void qemu_savevm_send_colo_enable(QEMUFile *f)
> {
> trace_savevm_send_colo_enable();
> @@ -1113,6 +1127,28 @@ void qemu_savevm_state_header(QEMUFile *f)
> }
> }
>
> +bool qemu_savevm_state_guest_unplug_pending(void)
> +{
> + int nr_failover_devs;
> + SaveStateEntry *se;
> + bool ret = false;
> + int n = 0;
> +
> + nr_failover_devs = qemu_savevm_nr_failover_devices();
> +
> + QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {
> + if (!se->vmsd || !se->vmsd->dev_unplug_pending) {
> + continue;
> + }
> + ret = se->vmsd->dev_unplug_pending(se->opaque);
> + if (!ret) {
> + n++;
> + }
> + }
> +
> + return n == nr_failover_devs;
> +}
> +
> void qemu_savevm_state_setup(QEMUFile *f)
> {
> SaveStateEntry *se;
> diff --git a/migration/savevm.h b/migration/savevm.h
> index 51a4b9caa8..ba64a7e271 100644
> --- a/migration/savevm.h
> +++ b/migration/savevm.h
> @@ -31,6 +31,7 @@
>
> bool qemu_savevm_state_blocked(Error **errp);
> void qemu_savevm_state_setup(QEMUFile *f);
> +bool qemu_savevm_state_guest_unplug_pending(void);
> int qemu_savevm_state_resume_prepare(MigrationState *s);
> void qemu_savevm_state_header(QEMUFile *f);
> int qemu_savevm_state_iterate(QEMUFile *f, bool postcopy);
> diff --git a/qapi/migration.json b/qapi/migration.json
> index 52e69e2868..5a06cd489f 100644
> --- a/qapi/migration.json
> +++ b/qapi/migration.json
> @@ -133,6 +133,9 @@
> # @device: During device serialisation when pause-before-switchover is
> enabled
> # (since 2.11)
> #
> +# @wait-unplug: wait for device unplug request by guest OS to be completed.
> +# (since 4.2)
> +#
> # Since: 2.3
> #
> ##
> @@ -140,7 +143,7 @@
> 'data': [ 'none', 'setup', 'cancelling', 'cancelled',
> 'active', 'postcopy-active', 'postcopy-paused',
> 'postcopy-recover', 'completed', 'failed', 'colo',
> - 'pre-switchover', 'device' ] }
> + 'pre-switchover', 'device', 'wait-unplug' ] }
>
> ##
> # @MigrationInfo:
> --
> 2.21.0
