Re: [PATCH v2 4/5] vdpa: Add virtio-net mac address via CVQ at start

[Jason Wang]

On Tue, Jul 19, 2022 at 12:30 AM Eugenio Pérez <eperezma@redhat.com> wrote:
>
> This is needed so the destination vdpa device see the same state a the
> guest set in the source.
>
> Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
> ---
>  include/net/vhost-vdpa.h |  1 +
>  hw/net/vhost_net.c       |  8 +++++
>  net/vhost-vdpa.c         | 64 ++++++++++++++++++++++++++++++++++++++--
>  3 files changed, 71 insertions(+), 2 deletions(-)
>
> diff --git a/include/net/vhost-vdpa.h b/include/net/vhost-vdpa.h
> index b81f9a6f2a..38d65e845d 100644
> --- a/include/net/vhost-vdpa.h
> +++ b/include/net/vhost-vdpa.h
> @@ -15,6 +15,7 @@
>  #define TYPE_VHOST_VDPA "vhost-vdpa"
>
>  struct vhost_net *vhost_vdpa_get_vhost_net(NetClientState *nc);
> +int vhost_vdpa_start(NetClientState *nc);
>
>  extern const int vdpa_feature_bits[];
>
> diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
> index ccac5b7a64..f9cebd9716 100644
> --- a/hw/net/vhost_net.c
> +++ b/hw/net/vhost_net.c
> @@ -274,6 +274,13 @@ static int vhost_net_start_one(struct vhost_net *net,
>              }
>          }
>      }
> +
> +    if (net->nc->info->type == NET_CLIENT_DRIVER_VHOST_VDPA) {
> +        r = vhost_vdpa_start(net->nc);
> +        if (r < 0) {
> +            goto fail;
> +        }
> +    }

This seems tricky, I wonder if we can do this via NetClientInfo
instead of directly via the vhost layer?

Note that the virtio-net has several places that check VDPA backend
explicitly. This is suboptimal, I will post patch to hide them via
NetClientInfo.

>      return 0;
>  fail:
>      file.fd = -1;
> @@ -373,6 +380,7 @@ int vhost_net_start(VirtIODevice *dev, NetClientState 
> *ncs,
>          r = vhost_net_start_one(get_vhost_net(peer), dev);
>
>          if (r < 0) {
> +            vhost_net_stop_one(get_vhost_net(peer), dev);

This should not be correct. vhost_net_start_one() fail means the
device is not started, stop once again seems not again.

>              goto err_start;
>          }
>
> diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c
> index 533bd9f680..84e90f067a 100644
> --- a/net/vhost-vdpa.c
> +++ b/net/vhost-vdpa.c
> @@ -342,9 +342,12 @@ static virtio_net_ctrl_ack 
> vhost_vdpa_net_cvq_add(VhostShadowVirtqueue *svq,
>      virtio_net_ctrl_ack status;
>      size_t dev_written;
>      int r;
> -    void *unused = (void *)1;
>
> -    r = vhost_svq_add(svq, &dev_buffers[0], 1, &dev_buffers[1], 1, unused);
> +    /*
> +     * Add a fake non-NULL VirtQueueElement since we'll remove before SVQ
> +     * event loop can get it.
> +     */
> +    r = vhost_svq_add(svq, &dev_buffers[0], 1, &dev_buffers[1], 1, (void 
> *)1);

Any reason we can 't simply pass NULL as the last parameter for vhost_svq_add()?

Thanks

>      if (unlikely(r != 0)) {
>          if (unlikely(r == -ENOSPC)) {
>              qemu_log_mask(LOG_GUEST_ERROR, "%s: No space on device queue\n",
> @@ -372,6 +375,63 @@ static virtio_net_ctrl_ack 
> vhost_vdpa_net_cvq_add(VhostShadowVirtqueue *svq,
>      return VIRTIO_NET_OK;
>  }
>
> +int vhost_vdpa_start(NetClientState *nc)
> +{
> +    VhostVDPAState *s = DO_UPCAST(VhostVDPAState, nc, nc);
> +    struct vhost_vdpa *v = &s->vhost_vdpa;
> +    VirtIONet *n = VIRTIO_NET(v->dev->vdev);
> +    uint64_t features = v->dev->vdev->host_features;
> +    VhostShadowVirtqueue *svq;
> +
> +    if (!v->shadow_vqs_enabled) {
> +        return 0;
> +    }
> +
> +    if (v->dev->vq_index + v->dev->nvqs != v->dev->vq_index_end) {
> +        /* Only interested in CVQ */
> +        return 0;
> +    }
> +
> +    assert(nc->info->type == NET_CLIENT_DRIVER_VHOST_VDPA);
> +
> +    svq = g_ptr_array_index(v->shadow_vqs, 0);
> +    if (features & BIT_ULL(VIRTIO_NET_F_CTRL_MAC_ADDR)) {
> +        const struct virtio_net_ctrl_hdr ctrl = {
> +            .class = VIRTIO_NET_CTRL_MAC,
> +            .cmd = VIRTIO_NET_CTRL_MAC_ADDR_SET,
> +        };
> +        uint8_t mac[6];
> +        const struct iovec out[] = {
> +            {
> +                .iov_base = (void *)&ctrl,
> +                .iov_len = sizeof(ctrl),
> +            },{
> +                .iov_base = mac,
> +                .iov_len = sizeof(mac),
> +            },
> +        };
> +        struct iovec dev_buffers[2] = {
> +            { .iov_base = s->cvq_cmd_out_buffer },
> +            { .iov_base = s->cvq_cmd_in_buffer },
> +        };
> +        bool ok;
> +        virtio_net_ctrl_ack state;
> +
> +        ok = vhost_vdpa_net_cvq_map_sg(s, out, ARRAY_SIZE(out), dev_buffers);
> +        if (unlikely(!ok)) {
> +            return -1;
> +        }
> +
> +        memcpy(mac, n->mac, sizeof(mac));
> +        state = vhost_vdpa_net_cvq_add(svq, dev_buffers);
> +        vhost_vdpa_cvq_unmap_buf(v, dev_buffers[0].iov_base);
> +        vhost_vdpa_cvq_unmap_buf(v, dev_buffers[1].iov_base);
> +        return state == VIRTIO_NET_OK ? 0 : 1;
> +    }
> +
> +    return 0;
> +}
> +
>  /**
>   * Do not forward commands not supported by SVQ. Otherwise, the device could
>   * accept it and qemu would not know how to update the device model.
> --
> 2.31.1
>