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[PATCH] vhost/net: Set num_buffers for virtio 1.0

Akihiko Odaki posted 1 patch 2 months, 2 weeks ago 
drivers/vhost/net.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
[PATCH] vhost/net: Set num_buffers for virtio 1.0
Posted by Akihiko Odaki 2 months, 2 weeks ago 
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@daynix.com>
---
 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@daynix.com>
Re: [PATCH] vhost/net: Set num_buffers for virtio 1.0
Posted by Michael S. Tsirkin 3 weeks, 2 days ago 
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@daynix.com>

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@daynix.com>
Re: [PATCH] vhost/net: Set num_buffers for virtio 1.0
Posted by Jason Wang 2 weeks, 4 days ago 
On Wed, Nov 6, 2024 at 4:54 PM Michael S. Tsirkin <mst@redhat.com> 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@daynix.com>
>
> 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@daynix.com>
>

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