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Re: [Qemu-devel] [PATCH v3] virtio-pci: Fix cross-version migration with
From: |
Stefan Hajnoczi |
Subject: |
Re: [Qemu-devel] [PATCH v3] virtio-pci: Fix cross-version migration with older machines |
Date: |
Thu, 15 Dec 2016 07:38:09 +0000 |
User-agent: |
Mutt/1.7.1 (2016-10-04) |
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 <address@hidden>
> Suggested-by: Stefan Hajnoczi <address@hidden>
> Cc: Michael S. Tsirkin <address@hidden>
> Cc: Cornelia Huck <address@hidden>
> Cc: Dr. David Alan Gilbert <address@hidden>
> Reviewed-by: Marcel Apfelbaum <address@hidden>
> Reviewed-by: Stefan Hajnoczi <address@hidden>
> Tested-by: Michael Roth <address@hidden>
> Signed-off-by: Maxime Coquelin <address@hidden>
> ---
>
> 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
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