On Tuesday, 2023-01-24 at 17:11:59 +01, Eugenio Pérez wrote: > Since GUEST_ANNOUNCE is emulated the feature bit could be set without > backend support. This happens in the vDPA case. > > However, backend vDPA parent may not have CVQ support. This causes an > incoherent feature set, and the driver may refuse to start. This > happens in virtio-net Linux driver.
Could you now simplify the tests in virtio_net_announce() and virtio_net_post_load_device() to look only for the presence of GUEST_ANNOUNCE, given that you can now presume that it implies CTRL_VQ? But anyway: Reviewed-by: David Edmondson <david.edmond...@oracle.com> > This may be solved differently in the future. Qemu is able to emulate a > CVQ just for guest_announce purposes, helping guest to notify the new > location with vDPA devices that does not support it. However, this is > left as a TODO as it is way more complex to backport. > > Tested with vdpa_net_sim, toggling manually VIRTIO_NET_F_CTRL_VQ in the > driver and migrating it with x-svq=on. > > Fixes: 980003debddd ("vdpa: do not handle VIRTIO_NET_F_GUEST_ANNOUNCE in > vhost-vdpa") > Reported-by: Dawar, Gautam <gautam.da...@amd.com> > Signed-off-by: Eugenio Pérez <epere...@redhat.com> > --- > hw/net/virtio-net.c | 15 +++++++++++++++ > 1 file changed, 15 insertions(+) > > diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c > index 3ae909041a..09d5c7a664 100644 > --- a/hw/net/virtio-net.c > +++ b/hw/net/virtio-net.c > @@ -820,6 +820,21 @@ static uint64_t virtio_net_get_features(VirtIODevice > *vdev, uint64_t features, > features |= (1ULL << VIRTIO_NET_F_MTU); > } > > + /* > + * Since GUEST_ANNOUNCE is emulated the feature bit could be set without > + * enabled. This happens in the vDPA case. > + * > + * Make sure the feature set is not incoherent, as the driver could > refuse > + * to start. > + * > + * TODO: QEMU is able to emulate a CVQ just for guest_announce purposes, > + * helping guest to notify the new location with vDPA devices that does > not > + * support it. > + */ > + if (!virtio_has_feature(vdev->backend_features, VIRTIO_NET_F_CTRL_VQ)) { > + virtio_clear_feature(&features, VIRTIO_NET_F_GUEST_ANNOUNCE); > + } > + > return features; > } -- Why stay in college? Why go to night school?