Introduce the control virtqueue support for vDPA shadow virtqueue. This
is needed for advanced networking features like rx filtering.
Virtio-net control VQ copies the descriptors to qemu's VA, so we avoid
TOCTOU with the guest's or device's memory every time there is a device
model change. Otherwise, the guest could change the memory content in
the time between qemu and the device read it.
To demonstrate command handling, VIRTIO_NET_F_CTRL_MACADDR is
implemented. If the virtio-net driver changes MAC the virtio-net device
model will be updated with the new one, and a rx filtering change event
will be raised.
More cvq commands could be added here straightforwardly but they have
not been tested.
Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
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