Page reporting features were never supported by legacy hypervisors. Supporting them poses a problem: should we use native endian-ness (like current code assumes)? Or little endian-ness like the virtio spec says? Rather than try to figure out, and since results of incorrect endian-ness are dire, let's just block this configuration.
Cc: stable@vger.kernel.org Signed-off-by: Michael S. Tsirkin mst@redhat.com --- drivers/virtio/virtio_balloon.c | 9 +++++++++ 1 file changed, 9 insertions(+)
diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c index 5d4b891bf84f..b9bc03345157 100644 --- a/drivers/virtio/virtio_balloon.c +++ b/drivers/virtio/virtio_balloon.c @@ -1107,6 +1107,15 @@ static int virtballoon_restore(struct virtio_device *vdev)
static int virtballoon_validate(struct virtio_device *vdev) { + /* + * Legacy devices never specified how modern features should behave. + * E.g. which endian-ness to use? Better not to assume anything. + */ + if (!virtio_has_feature(vdev, VIRTIO_F_VERSION_1)) { + __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT); + __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_PAGE_POISON); + __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_REPORTING); + } /* * Inform the hypervisor that our pages are poisoned or * initialized. If we cannot do that then we should disable