From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: [PATCH] virtio_balloon: clear modern features under legacy Date: Fri, 10 Jul 2020 07:31:34 -0400 Message-ID: <20200710113046.421366-1-mst@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline Sender: stable-owner@vger.kernel.org To: linux-kernel@vger.kernel.org Cc: stable@vger.kernel.org, David Hildenbrand , Jason Wang , virtualization@lists.linux-foundation.org, Alexander Duyck List-Id: virtualization@lists.linuxfoundation.org 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 --- 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 -- MST