On 2020/7/10 下午7:31, Michael S. Tsirkin wrote:
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@xxxxxxxxxxxxxxx
Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
---
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
Acked-by: Jason Wang <jasowang@xxxxxxxxxx>
