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?
> ---
> 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>
