Re: [RFC PATCH v2 0/8] Guest announce feature emulation using Shadow VirtQueue

[Jason Wang]

On Wed, Oct 19, 2022 at 8:52 PM Eugenio Pérez <eperezma@redhat.com> wrote:
>
> A gratuitous ARP is recommended after a live migration to reduce the amount of
> time needed by the network links to be aware of the new location.

A question: I think we need to deal with the case when GUSET_ANNOUNCE
is not negotiated? E.d sending the gARP by ourselves via vhost-vDPA?

Thanks

> A hypervisor
> may not have the knowledge of the guest network configuration, and this is
> especially true on passthrough devices, so its simpler to ask the guest to
> do it.
>
> However, the device control part of this feature can be totally emulated by
> qemu and shadow virtqueue, not needing any special feature from the actual
> vdpa device.
>
> VIRTIO_NET_F_STATUS is also needed for the guest to access the status of
> virtio net config where announcement status bit is set. Emulating it as
> always active in case backend does not support it.
>
> v2:
> * Add VIRTIO_NET_F_STATUS emulation.
>
> Eugenio Pérez (8):
>   vdpa: Delete duplicated vdpa_feature_bits entry
>   vdpa: Save emulated features list in vhost_vdpa
>   vhost_net: Emulate link state up if backend doesn't expose it
>   vdpa: Expose VIRTIO_NET_F_STATUS unconditionally
>   vdpa: Remove shadow CVQ command check
>   vdpa: handle VIRTIO_NET_CTRL_ANNOUNCE in
>     vhost_vdpa_net_handle_ctrl_avail
>   vhost_net: return VIRTIO_NET_S_ANNOUNCE is device model has it set
>   vdpa: Offer VIRTIO_NET_F_GUEST_ANNOUNCE feature if SVQ is enabled
>
>  include/hw/virtio/vhost-vdpa.h |  2 +
>  hw/net/vhost_net.c             | 35 +++++++++++++++-
>  hw/virtio/vhost-vdpa.c         |  8 ++--
>  net/vhost-vdpa.c               | 74 ++++++++++------------------------
>  4 files changed, 62 insertions(+), 57 deletions(-)
>
> --
> 2.31.1
>
>