Re: [PATCH v1 06/13] migrate/ram: Discard new RAM when growing RAM blocks and the VM is stopped

[David Hildenbrand]

On 19.02.20 17:17, David Hildenbrand wrote:
> In case we grow our RAM after ram_postcopy_incoming_init() (e.g., when
> synchronizing the RAM block state with the migration source), the resized
> part would not get discarded. Let's perform that when being notified
> about a resize while postcopy has been advised and the guest is not
> running yet.
> 
> Cc: "Dr. David Alan Gilbert" <address@hidden>
> Cc: Juan Quintela <address@hidden>
> Cc: Peter Xu <address@hidden>
> Signed-off-by: David Hildenbrand <address@hidden>
> ---
>  migration/ram.c | 19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
> 
> diff --git a/migration/ram.c b/migration/ram.c
> index 57f32011a3..cbd54947fb 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -3722,6 +3722,25 @@ static void ram_mig_ram_block_resized(RAMBlockNotifier 
> *n, void *host,
>          return;
>      }
>  
> +    /*
> +     * Especially at the start of precopy on the migration target, before
> +     * starting postcopy, we synchronize the RAM block sizes. Let's make sure
> +     * that any resizes before starting the guest are properly handled by
> +     * postcopy. Note: All other postcopy handling (e.g., registering 
> handlers,
> +     * disabling THP) happens after all resizes (e.g., during precopy) were
> +     * performed.
> +     */

I think it would be clearer to do a

ps >= POSTCOPY_INCOMING_ADVISE && ps < POSTCOPY_INCOMING_RUNNING

We really only want to do something when psotcopy has been advised but
the guest is not running yet.

Will look into that as I find ways to actually test this :)

-- 
Thanks,

David / dhildenb