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

[Andrey Gruzdev <andrey.gruzdev@virtuozzo.com>]

On 18.03.2021 21:16, David Hildenbrand wrote:
> 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!

-- 
Andrey Gruzdev, Principal Engineer
Virtuozzo GmbH  +7-903-247-6397
                 virtuzzo.com