On 12/15/2016 11:31 AM, Stefan Hajnoczi wrote:
On Thu, Dec 15, 2016 at 09:26:56AM +0100, Cornelia Huck wrote:
On Thu, 15 Dec 2016 07:38:09 +0000
Stefan Hajnoczi <[email protected]> wrote:
On Wed, Dec 14, 2016 at 05:30:35PM +0100, Maxime Coquelin wrote:
This patch fixes a cross-version migration regression introduced
by commit d1b4259f ("virtio-bus: Plug devices after features are
negotiated").
The problem is encountered when host's vhost backend does not support
VIRTIO_F_VERSION_1, and migration is initiated from a v2.7 or prior
machine with virtio-pci modern capabilities enabled to a v2.8 machine.
In this case, modern capabilities get exposed to the guest by the source,
whereas the target will detect version 1 is not supported so will only
expose legacy capabilities.
The problem is fixed by introducing a new "x-ignore-backend-features"
property, which is set in v2.7 and prior compatibility modes. Doing this,
v2.7 machine keeps its broken behaviour (enabling modern while version
is not supported), and newer machines will behave correctly.
Reported-by: Michael Roth <[email protected]>
Suggested-by: Stefan Hajnoczi <[email protected]>
Cc: Michael S. Tsirkin <[email protected]>
Cc: Cornelia Huck <[email protected]>
Cc: Dr. David Alan Gilbert <[email protected]>
Reviewed-by: Marcel Apfelbaum <[email protected]>
Reviewed-by: Stefan Hajnoczi <[email protected]>
Tested-by: Michael Roth <[email protected]>
Signed-off-by: Maxime Coquelin <[email protected]>
---
V3 fixes commit message with the new property name.
V2 changes the naming as proposed by Michael T.and Cornelia, and
fixes commit message.
hw/virtio/virtio-pci.c | 5 ++++-
hw/virtio/virtio-pci.h | 1 +
include/hw/compat.h | 4 ++++
3 files changed, 9 insertions(+), 1 deletion(-)
Thanks, applied to my staging tree:
https://github.com/stefanha/qemu/commits/staging
Stefan
Hm, missing my R-b I gave for v2... feel free to add
Reviewed-by: Cornelia Huck <[email protected]>
if you still want to change it.
Sorry, the R-b didn't make it into v2.8.0-rc4.
The patch management scripts I use apply all R-b for a single email
thread. They do not look at previous revisions (it would be hard to
tell which R-b still stand and which do not). The usual solution is for
the patch author to include previous R-b in new revisions as long as
code changes aren't substantial.
Right that's my fault, sorry Cornelia.
Maxime
Stefan
