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

[Juan Quintela <quintela@redhat.com>]

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>
> ---
>  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 {

I agree with the idea.  But if we are getting out due to timeout == 0,
shouldn't we return some error, warning, whatever?

Later, Juan.