Re: [Qemu-devel] [PATCH-for-4.1 v2 3/3] virtio-balloon: reset pbp on device resets

[David Gibson <david@gibson.dropbear.id.au>]

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On Wed, Jul 17, 2019 at 12:35:50PM +0200, David Hildenbrand wrote:
> When a guest reboots (ordinary reboots, but also via kexec), it will
> happily reuse any system memory, including previously inflated memory.
> 
> We could have tracking data for a pbp (PartiallyBalloonedPage). It could
> happen that a new inflation request from the guest will result in a
> discard of such a pbp, although the guest is (again) reusing some
> memory.
> 
> We should reset the pbp on any device resets.
> 
> Fixes: ed48c59875b6 ("virtio-balloon: Safely handle BALLOON_PAGE_SIZE <
>                      host page size")
> Cc: qemu-stable@nongnu.org #v4.0.0
> Cc: Stefan Hajnoczi <stefanha@redhat.com>
> Cc: David Gibson <david@gibson.dropbear.id.au>
> Cc: Michael S. Tsirkin <mst@redhat.com>
> Cc: Igor Mammedov <imammedo@redhat.com>
> Signed-off-by: David Hildenbrand <david@redhat.com>

Acked-by: David Gibson <david@gibson.dropbear.id.au>

> ---
>  hw/virtio/virtio-balloon.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c
> index 84d01bceb3..9de3c030bf 100644
> --- a/hw/virtio/virtio-balloon.c
> +++ b/hw/virtio/virtio-balloon.c
> @@ -847,6 +847,7 @@ static void virtio_balloon_device_reset(VirtIODevice *vdev)
>      if (virtio_balloon_free_page_support(s)) {
>          virtio_balloon_free_page_stop(s);
>      }
> +    virtio_balloon_reset_pbp(s);
>  
>      if (s->stats_vq_elem != NULL) {
>          virtqueue_unpop(s->svq, s->stats_vq_elem, 0);

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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