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qemu/hw/virtio
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Maxime Coquelin 66d1c4c19f virtio-pci: Fix cross-version migration with older machines 
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 <mdroth@linux.vnet.ibm.com>
Reviewed-by: Marcel Apfelbaum <marcel@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Tested-by: Michael Roth <mdroth@linux.vnet.ibm.com>
Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Message-id: 20161214163035.3297-1-maxime.coquelin@redhat.com
Suggested-by: Stefan Hajnoczi <stefanha@redhat.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Cornelia Huck <cornelia.huck@de.ibm.com>
Cc: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Marcel Apfelbaum <marcel@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Tested-by: Michael Roth <mdroth@linux.vnet.ibm.com>
Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2016-12-15 07:35:19 +00:00
..
Makefile.objs virtio-crypto-pci: add virtio crypto pci support 2016-11-01 19:21:08 +02:00
trace-events virtio: set ISR on dataplane notifications 2016-11-18 17:29:25 +02:00
vhost-backend.c vhost-vsock: add virtio sockets device 2016-09-10 00:28:08 +03:00
vhost-user.c char: use qemu_chr_fe* functions with CharBackend argument 2016-10-24 15:27:21 +02:00
vhost-vsock.c virtio: cleanup VMSTATE_VIRTIO_DEVICE 2016-10-10 02:21:43 +03:00
vhost.c virtio: introduce grab/release_ioeventfd to fix vhost 2016-11-18 17:29:25 +02:00
virtio-balloon.c virtio: rename virtqueue_discard to virtqueue_unpop 2016-11-15 17:20:36 +02:00
virtio-bus.c virtio: introduce grab/release_ioeventfd to fix vhost 2016-11-18 17:29:25 +02:00
virtio-crypto-pci.c virtio-crypto: tag as not hotpluggable and migration 2016-11-15 17:20:36 +02:00
virtio-crypto.c virtio-crypto: fix uninitialized variables 2016-11-30 04:22:18 +02:00
virtio-mmio.c virtio: access ISR atomically 2016-11-18 17:29:25 +02:00
virtio-pci.c virtio-pci: Fix cross-version migration with older machines 2016-12-15 07:35:19 +00:00
virtio-pci.h virtio-pci: Fix cross-version migration with older machines 2016-12-15 07:35:19 +00:00
virtio-rng.c virtio: cleanup VMSTATE_VIRTIO_DEVICE 2016-10-10 02:21:43 +03:00
virtio.c virtio: set ISR on dataplane notifications 2016-11-18 17:29:25 +02:00