[libvirt PATCH v2 1/6] qemu: add capabilities flag for failover feature

[Daniel P. Berrangé]

On Fri, Jan 24, 2020 at 10:39:16AM -0500, Laine Stump wrote:
> Presence of the virtio-net-pci option called "failover" indicates
> support in a qemu binary of a simplistic bonding of a virtio-net
> device with another PCI device. This feature allows migration of
> guests that have a network device assigned to a guest with VFIO, by
> creating a network bond device in the guest consisting of the
> VFIO-assigned device and a virtio-net-pci device, then temporarily
> (and automatically) unplugging the VFIO net device prior to migration
> (and hotplugging an equivalent device on the migration
> destination). (The feature is called "failover" because the bond
> device uses the vfio-pci netdev for normal guest networking, but
> "fails over" to the virtio-net-pci netdev once the vfio-pci device is
> unplugged for migration.)
> 
> Full functioning of the feature also requires support in the
> virtio-net driver in the guest OS (since that is where the bond device
> resides), but if the "failover" commandline option is present for the
> virtio-net-pci device in qemu, at least the qemu part of the feature
> is available, and libvirt can add the proper options to both the
> virtio-net-pci and vfio-pci device commandlines to indicate qemu
> should attempt doing the failover during migration.
> 
> This patch just adds the qemu capabilities flag "virtio-net.failover".
> 
> Signed-off-by: Laine Stump <laine at redhat.com>
> ---
> 
> No change from V1.
> 
>  src/qemu/qemu_capabilities.c                      | 4 ++++
>  src/qemu/qemu_capabilities.h                      | 3 +++
>  tests/qemucapabilitiesdata/caps_4.2.0.aarch64.xml | 1 +
>  tests/qemucapabilitiesdata/caps_4.2.0.x86_64.xml  | 1 +
>  4 files changed, 9 insertions(+)

Reviewed-by: Daniel P. Berrangé <berrange at redhat.com>


Regards,
Daniel
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