Re: [PATCH 2/3] migration: Inhibit virtio-balloon for the duration of background snapshot

[David Hildenbrand]

On 18.03.21 18:46, Andrey Gruzdev wrote:
> The same thing as for incoming postcopy - we cannot deal with concurrent
> RAM discards when using background snapshot feature in outgoing migration.
>
> Signed-off-by: Andrey Gruzdev <andrey.gruzdev@virtuozzo.com>
> ---
>   hw/virtio/virtio-balloon.c | 8 ++++++--
>   include/migration/misc.h   | 2 ++
>   migration/migration.c      | 8 ++++++++
>   3 files changed, 16 insertions(+), 2 deletions(-)
>
> diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c
> index e770955176..d120bf8f43 100644
> --- a/hw/virtio/virtio-balloon.c
> +++ b/hw/virtio/virtio-balloon.c
> @@ -66,8 +66,12 @@ static bool 
> virtio_balloon_pbp_matches(PartiallyBalloonedPage *pbp,
>   
>   static bool virtio_balloon_inhibited(void)
>   {
> -    /* Postcopy cannot deal with concurrent discards, so it's special. */
> -    return ram_block_discard_is_disabled() || migration_in_incoming_postcopy();
> +    /*
> +     * Postcopy cannot deal with concurrent discards,
> +     * so it's special, as well as background snapshots.
> +     */
> +    return ram_block_discard_is_disabled() || migration_in_incoming_postcopy() 
> ||
> +            migration_in_bg_snapshot();
>   }
>   
>   static void balloon_inflate_page(VirtIOBalloon *balloon,
> diff --git a/include/migration/misc.h b/include/migration/misc.h
> index bccc1b6b44..738675ef52 100644
> --- a/include/migration/misc.h
> +++ b/include/migration/misc.h
> @@ -70,6 +70,8 @@ bool migration_in_postcopy_after_devices(MigrationState *);
>   void migration_global_dump(Monitor *mon);
>   /* True if incomming migration entered POSTCOPY_INCOMING_DISCARD */
>   bool migration_in_incoming_postcopy(void);
> +/* True if background snapshot is active */
> +bool migration_in_bg_snapshot(void);
>   
>   /* migration/block-dirty-bitmap.c */
>   void dirty_bitmap_mig_init(void);
> diff --git a/migration/migration.c b/migration/migration.c
> index 496cf6e17b..656d6249a6 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -1976,6 +1976,14 @@ bool migration_in_incoming_postcopy(void)
>       return ps >= POSTCOPY_INCOMING_DISCARD && ps < POSTCOPY_INCOMING_END;
>   }
>   
> +bool migration_in_bg_snapshot(void)
> +{
> +    MigrationState *s = migrate_get_current();
> +
> +    return migrate_background_snapshot() &&
> +            migration_is_setup_or_active(s->state);
> +}
> +
>   bool migration_is_idle(void)
>   {
>       MigrationState *s = current_migration;

Reviewed-by: David Hildenbrand <david@redhat.com>

--
Thanks,

David / dhildenb