Re: [Qemu-devel] [PATCH 05/14] virtio-net: use safe iov operations for rx

[Anthony Liguori <anthony@codemonkey.ws>]

"Michael S. Tsirkin" <mst@redhat.com> writes:

> Avoid magling iov manually: use safe iov operations
> for processing packets incoming to guest.
> This also removes the requirement for virtio header to
> fit the first s/g entry exactly.
>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

Reviewed-by: Anthony Liguori <aliguori@us.ibm.com>

Regards,

Anthony Liguori

> ---
>  hw/virtio-net.c | 25 ++++++++++++++-----------
>  1 file changed, 14 insertions(+), 11 deletions(-)
>
> diff --git a/hw/virtio-net.c b/hw/virtio-net.c
> index 6e53858..9611d95 100644
> --- a/hw/virtio-net.c
> +++ b/hw/virtio-net.c
> @@ -593,8 +593,9 @@ static int receive_filter(VirtIONet *n, const uint8_t *buf, int size)
>  static ssize_t virtio_net_receive(NetClientState *nc, const uint8_t *buf, size_t size)
>  {
>      VirtIONet *n = DO_UPCAST(NICState, nc, nc)->opaque;
> -    struct virtio_net_hdr_mrg_rxbuf *mhdr = NULL;
> -    const struct iovec *sg = elem.in_sg;
> +    struct iovec mhdr_sg[VIRTQUEUE_MAX_SIZE];
> +    struct virtio_net_hdr_mrg_rxbuf mhdr;
> +    unsigned mhdr_cnt = 0;
>      size_t offset, i, guest_offset;
>  
>      if (!virtio_net_can_receive(&n->nic->nc))
> @@ -632,14 +633,13 @@ static ssize_t virtio_net_receive(NetClientState *nc, const uint8_t *buf, size_t
>              exit(1);
>          }
>  
> -        if (!n->mergeable_rx_bufs && elem.in_sg[0].iov_len != n->guest_hdr_len) {
> -            error_report("virtio-net header not in first element");
> -            exit(1);
> -        }
> -
>          if (i == 0) {
> -            if (n->mergeable_rx_bufs)
> -                mhdr = (struct virtio_net_hdr_mrg_rxbuf *)sg[0].iov_base;
> +            if (n->mergeable_rx_bufs) {
> +                mhdr_cnt = iov_cpy(mhdr_sg, ARRAY_SIZE(mhdr_sg),
> +                                   sg, elem.in_num,
> +                                   offsetof(typeof(mhdr), num_buffers),
> +                                   sizeof(mhdr.num_buffers));
> +            }
>  
>              offset += receive_header(n, sg, elem.in_num,
>                                       buf + offset, size - offset);
> @@ -672,8 +672,11 @@ static ssize_t virtio_net_receive(NetClientState *nc, const uint8_t *buf, size_t
>          virtqueue_fill(n->rx_vq, &elem, total, i++);
>      }
>  
> -    if (mhdr) {
> -        stw_p(&mhdr->num_buffers, i);
> +    if (mhdr_cnt) {
> +        stw_p(&mhdr.num_buffers, i);
> +        iov_from_buf(mhdr_sg, mhdr_cnt,
> +                     0,
> +                     &mhdr.num_buffers, sizeof mhdr.num_buffers);
>      }
>  
>      virtqueue_flush(n->rx_vq, i);
> -- 
> MST