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Tsirkin" To: Akihiko Odaki Cc: Jason Wang , Eugenio =?iso-8859-1?Q?P=E9rez?= , kvm@vger.kernel.org, virtualization@lists.linux.dev, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] vhost/net: Set num_buffers for virtio 1.0 Message-ID: <20241106035029-mutt-send-email-mst@kernel.org> References: <20240915-v1-v1-1-f10d2cb5e759@daynix.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240915-v1-v1-1-f10d2cb5e759@daynix.com> 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 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