From: "Michael S. Tsirkin" <mst@redhat.com>
To: linux-kernel@vger.kernel.org
Cc: stable@vger.kernel.org, David Hildenbrand <david@redhat.com>,
Jason Wang <jasowang@redhat.com>,
virtualization@lists.linux-foundation.org,
Alexander Duyck <alexander.duyck@gmail.com>
Subject: [PATCH] virtio_balloon: clear modern features under legacy
Date: Fri, 10 Jul 2020 07:31:34 -0400 [thread overview]
Message-ID: <20200710113046.421366-1-mst@redhat.com> (raw)
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
--
MST
next reply other threads:[~2020-07-10 11:31 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-10 11:31 Michael S. Tsirkin [this message]
2020-07-10 11:32 ` [PATCH] virtio_balloon: clear modern features under legacy David Hildenbrand
2020-07-10 16:13 ` Alexander Duyck
2020-07-12 15:09 ` Michael S. Tsirkin
2020-07-13 15:10 ` Alexander Duyck
2020-07-14 8:45 ` Michael S. Tsirkin
2020-07-14 17:31 ` Alexander Duyck
2020-07-15 9:46 ` Michael S. Tsirkin
2020-07-13 3:36 ` Jason Wang
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