Re: [PATCH 2/2] migration: failover: continue to wait card unplug on error

[Dr. David Alan Gilbert]

* Laurent Vivier (lvivier@redhat.com) wrote:
> If the user cancels the migration in the unplug-wait state,
> QEMU will try to plug back the card and this fails because the card
> is partially unplugged.
> To avoid the problem, continue to wait the card unplug, but to
> allow the migration to be canceled if the card never finishes to unplug
> use a timeout.
> 
> Bug: https://bugzilla.redhat.com/show_bug.cgi?id=1976852
> Signed-off-by: Laurent Vivier <lvivier@redhat.com>

I'll take this for now, but as Juan says, we could really do with some
diags when this happens, so when someone comes and tells us that
the hotplug has failed we can see.  Please send something to add it.


Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

> ---
>  migration/migration.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/migration/migration.c b/migration/migration.c
> index 3e92c405a2b6..3b06d43a7f42 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -3679,6 +3679,17 @@ static void qemu_savevm_wait_unplug(MigrationState *s, 
> int old_state,
>                 qemu_savevm_state_guest_unplug_pending()) {
>              qemu_sem_timedwait(&s->wait_unplug_sem, 250);
>          }
> +        if (s->state != MIGRATION_STATUS_WAIT_UNPLUG) {
> +            int timeout = 120; /* 30 seconds */
> +            /*
> +             * migration has been canceled
> +             * but as we have started an unplug we must wait the end
> +             * to be able to plug back the card
> +             */
> +            while (timeout-- && qemu_savevm_state_guest_unplug_pending()) {
> +                qemu_sem_timedwait(&s->wait_unplug_sem, 250);
> +            }
> +        }
>  
>          migrate_set_state(&s->state, MIGRATION_STATUS_WAIT_UNPLUG, 
> new_state);
>      } else {
> -- 
> 2.31.1
> 
> 
-- 
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK