On Wed, Oct 19, 2022 at 8:52 PM Eugenio Pérez <epere...@redhat.com> wrote:
>
> At this moment this code path is not reached, but vdpa devices can offer
> VIRTIO_NET_F_STATUS unconditionally.
So I guess what you mean is that, for the parent that doesn't support
VIRTIO_NET_F_STATUS, emulate one for making sure the ANNOUCNE to work.
This is safe since the spec said the driver will assume the link is
always up if without this feature.
> While the guest must assume that
> link is always up by the standard, qemu will set the status bit to 1
> always in this case.
>
> This makes little use by itself, but VIRTIO_NET_F_STATUS is needed for
> the guest to read status bit VIRTIO_NET_F_GUEST_ANNOUNCE, used by feature
> VIRTIO_NET_F_GUEST_ANNOUNCE. So qemu must emulate status feature in case
> it needs to emulate the guest announce feature.
>
> Signed-off-by: Eugenio Pérez <epere...@redhat.com>
> ---
> hw/net/vhost_net.c | 27 ++++++++++++++++++++++++++-
> 1 file changed, 26 insertions(+), 1 deletion(-)
>
> diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
> index d28f8b974b..5660606c1d 100644
> --- a/hw/net/vhost_net.c
> +++ b/hw/net/vhost_net.c
> @@ -117,7 +117,32 @@ uint64_t vhost_net_get_features(struct vhost_net *net,
> uint64_t features)
> int vhost_net_get_config(struct vhost_net *net, uint8_t *config,
> uint32_t config_len)
> {
> - return vhost_dev_get_config(&net->dev, config, config_len, NULL);
> + VirtIODevice *vdev;
> + int r = vhost_dev_get_config(&net->dev, config, config_len, NULL);
> +
> + if (unlikely(r != 0)) {
> + return r;
> + }
> +
> + if (config_len < endof(struct virtio_net_config, status)) {
> + return 0;
> + }
> +
> + /*
> + * TODO: Perform this only if vhost_vdpa.
> + */
Cindy adds some mediation codes for vhost-vDPA in
virtio_net_get_config(), so I believe it can be done there?
Thanks
> + vdev = net->dev.vdev;
> + if (!vdev) {
> + /* Device is starting */
> + return 0;
> + }
> +
> + if ((net->dev.acked_features & BIT_ULL(VIRTIO_NET_F_STATUS)) &&
> + !(net->dev.features & BIT_ULL(VIRTIO_NET_F_STATUS))) {
> + ((struct virtio_net_config *)config)->status |= VIRTIO_NET_S_LINK_UP;
> + }
> +
> + return 0;
> }
> int vhost_net_set_config(struct vhost_net *net, const uint8_t *data,
> uint32_t offset, uint32_t size, uint32_t flags)
> --
> 2.31.1
>
