Re: [PATCH net-next v9 6/6] vhost/net: Support VIRTIO_NET_F_HASH_REPORT

[Akihiko Odaki]

On 2025/03/10 13:43, Jason Wang wrote:
> On Fri, Mar 7, 2025 at 7:02 PM Akihiko Odaki <akihiko.odaki@xxxxxxxxxx> wrote:
> > VIRTIO_NET_F_HASH_REPORT allows to report hash values calculated on the
> > host. When VHOST_NET_F_VIRTIO_NET_HDR is employed, it will report no
> > hash values (i.e., the hash_report member is always set to
> > VIRTIO_NET_HASH_REPORT_NONE). Otherwise, the values reported by the
> > underlying socket will be reported.
> >
> > VIRTIO_NET_F_HASH_REPORT requires VIRTIO_F_VERSION_1.
> >
> > Signed-off-by: Akihiko Odaki <akihiko.odaki@xxxxxxxxxx>
> > Tested-by: Lei Yang <leiyang@xxxxxxxxxx>
> > ---
> >   drivers/vhost/net.c | 49 +++++++++++++++++++++++++++++--------------------
> >   1 file changed, 29 insertions(+), 20 deletions(-)
> >
> > diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
> > index b9b9e9d40951856d881d77ac74331d914473cd56..16b241b44f89820a42c302f3586ea6bb5e0d4289 100644
> > --- a/drivers/vhost/net.c
> > +++ b/drivers/vhost/net.c
> > @@ -73,6 +73,7 @@ enum {
> >          VHOST_NET_FEATURES = VHOST_FEATURES |
> >                           (1ULL << VHOST_NET_F_VIRTIO_NET_HDR) |
> >                           (1ULL << VIRTIO_NET_F_MRG_RXBUF) |
> > +                        (1ULL << VIRTIO_NET_F_HASH_REPORT) |
> >                           (1ULL << VIRTIO_F_ACCESS_PLATFORM) |
> >                           (1ULL << VIRTIO_F_RING_RESET)
> >   };
> > @@ -1097,9 +1098,11 @@ static void handle_rx(struct vhost_net *net)
> >                  .msg_controllen = 0,
> >                  .msg_flags = MSG_DONTWAIT,
> >          };
> > -       struct virtio_net_hdr hdr = {
> > -               .flags = 0,
> > -               .gso_type = VIRTIO_NET_HDR_GSO_NONE
> > +       struct virtio_net_hdr_v1_hash hdr = {
> > +               .hdr = {
> > +                       .flags = 0,
> > +                       .gso_type = VIRTIO_NET_HDR_GSO_NONE
> > +               }
> >          };
> >          size_t total_len = 0;
> >          int err, mergeable;
> > @@ -1110,7 +1113,6 @@ static void handle_rx(struct vhost_net *net)
> >          bool set_num_buffers;
> >          struct socket *sock;
> >          struct iov_iter fixup;
> > -       __virtio16 num_buffers;
> >          int recv_pkts = 0;
> >
> >          mutex_lock_nested(&vq->mutex, VHOST_NET_VQ_RX);
> > @@ -1191,30 +1193,30 @@ static void handle_rx(struct vhost_net *net)
> >                          vhost_discard_vq_desc(vq, headcount);
> >                          continue;
> >                  }
> > +               hdr.hdr.num_buffers = cpu_to_vhost16(vq, headcount);
> >                  /* Supply virtio_net_hdr if VHOST_NET_F_VIRTIO_NET_HDR */
> >                  if (unlikely(vhost_hlen)) {
> > -                       if (copy_to_iter(&hdr, sizeof(hdr),
> > -                                        &fixup) != sizeof(hdr)) {
> > +                       if (copy_to_iter(&hdr, vhost_hlen,
> > +                                        &fixup) != vhost_hlen) {
> >                                  vq_err(vq, "Unable to write vnet_hdr "
> >                                         "at addr %p\n", vq->iov->iov_base);
> >                                  goto out;
>
> Is this an "issue" specific to RSS/HASH? If it's not, we need a separate patch.
>
> Honestly, I'm not sure if it's too late to fix this.

There is nothing wrong with the current implementation. The current 
implementation fills the header with zero except num_buffers, which it 
fills some real value. This functionality is working fine with 
VIRTIO_NET_F_MRG_RXBUF and VIRTIO_F_VERSION_1, which change the header size.

Now I'm adding VIRTIO_NET_F_HASH_REPORT and it adds the hash_report 
field, which also needs to be initialized with zero, so I'm making sure 
vhost_net will also initialize it.

Regards,
Akihiko Odaki

> Others look fine.
>
> Thanks