On Wed, Nov 6, 2024 at 4:54 PM Michael S. Tsirkin <mst@xxxxxxxxxx> wrote:
>
> On Sun, Sep 15, 2024 at 10:35:53AM +0900, Akihiko Odaki wrote:
> > The specification says the device MUST set num_buffers to 1 if
> > VIRTIO_NET_F_MRG_RXBUF has not been negotiated.
> >
> > Fixes: 41e3e42108bc ("vhost/net: enable virtio 1.0")
> > Signed-off-by: Akihiko Odaki <akihiko.odaki@xxxxxxxxxx>
>
> True, this is out of spec. But, qemu is also out of spec :(
>
> Given how many years this was out there, I wonder whether
> we should just fix the spec, instead of changing now.
>
> Jason, what's your take?
Fixing the spec (if you mean release the requirement) seems to be less risky.
Thanks
>
>
> > ---
> > drivers/vhost/net.c | 5 ++++-
> > 1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
> > index f16279351db5..d4d97fa9cc8f 100644
> > --- a/drivers/vhost/net.c
> > +++ b/drivers/vhost/net.c
> > @@ -1107,6 +1107,7 @@ static void handle_rx(struct vhost_net *net)
> > size_t vhost_hlen, sock_hlen;
> > size_t vhost_len, sock_len;
> > bool busyloop_intr = false;
> > + bool set_num_buffers;
> > struct socket *sock;
> > struct iov_iter fixup;
> > __virtio16 num_buffers;
> > @@ -1129,6 +1130,8 @@ static void handle_rx(struct vhost_net *net)
> > vq_log = unlikely(vhost_has_feature(vq, VHOST_F_LOG_ALL)) ?
> > vq->log : NULL;
> > mergeable = vhost_has_feature(vq, VIRTIO_NET_F_MRG_RXBUF);
> > + set_num_buffers = mergeable ||
> > + vhost_has_feature(vq, VIRTIO_F_VERSION_1);
> >
> > do {
> > sock_len = vhost_net_rx_peek_head_len(net, sock->sk,
> > @@ -1205,7 +1208,7 @@ static void handle_rx(struct vhost_net *net)
> > /* TODO: Should check and handle checksum. */
> >
> > num_buffers = cpu_to_vhost16(vq, headcount);
> > - if (likely(mergeable) &&
> > + if (likely(set_num_buffers) &&
> > copy_to_iter(&num_buffers, sizeof num_buffers,
> > &fixup) != sizeof num_buffers) {
> > vq_err(vq, "Failed num_buffers write");
> >
> > ---
> > base-commit: 46a0057a5853cbdb58211c19e89ba7777dc6fd50
> > change-id: 20240908-v1-90fc83ff8b09
> >
> > Best regards,
> > --
> > Akihiko Odaki <akihiko.odaki@xxxxxxxxxx>
>
