From: "Michael S. Tsirkin" <mst@redhat.com>
Date: Sun, 5 Jan 2020 08:22:07 -0500

The only way for guest to control offloads (as enabled by
VIRTIO_NET_F_CTRL_GUEST_OFFLOADS) is by sending commands
through CTRL_VQ. So it does not make sense to
acknowledge VIRTIO_NET_F_CTRL_GUEST_OFFLOADS without
VIRTIO_NET_F_CTRL_VQ.

The spec does not outlaw devices with such a configuration, so we have
to support it. Simply clear VIRTIO_NET_F_CTRL_GUEST_OFFLOADS.
Note that Linux is still crashing if it tries to
change the offloads when there's no control vq.
That needs to be fixed by another patch.

Reported-by: Alistair Delva <redacted>
Reported-by: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
Fixes: 3f93522ffab2 ("virtio-net: switch off offloads on demand if possible on XDP set")
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---

Same patch as v1 but update documentation so it's clear it's not
enough to fix the crash.

Where are we with this patch?  There seems to still be some unresolved
discussion about how we should actually handle this case.

Thanks.