Re: [Qemu-devel] [QEMU PATCH v4 1/3] virtio-net: remove layout assumptions for ctrl vq

[Stefan Hajnoczi]

On Sat, Jan 19, 2013 at 09:54:26AM +0800, address@hidden wrote:
> From: "Michael S. Tsirkin" <address@hidden>
> 
> Virtio-net code makes assumption about virtqueue descriptor layout
> (e.g. sg[0] is the header, sg[1] is the data buffer).
> 
> This patch makes code not rely on the layout of descriptors.
> 
> Signed-off-by: Michael S. Tsirkin <address@hidden>
> Signed-off-by: Amos Kong <address@hidden>
> ---
>  hw/virtio-net.c | 128 
> ++++++++++++++++++++++++++++++++------------------------
>  1 file changed, 74 insertions(+), 54 deletions(-)
> 
> diff --git a/hw/virtio-net.c b/hw/virtio-net.c
> index 3bb01b1..113e194 100644
> --- a/hw/virtio-net.c
> +++ b/hw/virtio-net.c
> @@ -315,44 +315,44 @@ static void virtio_net_set_features(VirtIODevice *vdev, 
> uint32_t features)
>  }
>  
>  static int virtio_net_handle_rx_mode(VirtIONet *n, uint8_t cmd,
> -                                     VirtQueueElement *elem)
> +                                     struct iovec *iov, unsigned int iov_cnt)
>  {
>      uint8_t on;
> +    size_t s;
>  
> -    if (elem->out_num != 2 || elem->out_sg[1].iov_len != sizeof(on)) {
> -        error_report("virtio-net ctrl invalid rx mode command");
> -        exit(1);
> +    s = iov_to_buf(iov, iov_cnt, 0, &on, sizeof(on));
> +    if (s != sizeof(on)) {
> +        return VIRTIO_NET_ERR;
>      }
>  
> -    on = ldub_p(elem->out_sg[1].iov_base);
> -
> -    if (cmd == VIRTIO_NET_CTRL_RX_MODE_PROMISC)
> +    if (cmd == VIRTIO_NET_CTRL_RX_MODE_PROMISC) {
>          n->promisc = on;
> -    else if (cmd == VIRTIO_NET_CTRL_RX_MODE_ALLMULTI)
> +    } else if (cmd == VIRTIO_NET_CTRL_RX_MODE_ALLMULTI) {
>          n->allmulti = on;
> -    else if (cmd == VIRTIO_NET_CTRL_RX_MODE_ALLUNI)
> +    } else if (cmd == VIRTIO_NET_CTRL_RX_MODE_ALLUNI) {
>          n->alluni = on;
> -    else if (cmd == VIRTIO_NET_CTRL_RX_MODE_NOMULTI)
> +    } else if (cmd == VIRTIO_NET_CTRL_RX_MODE_NOMULTI) {
>          n->nomulti = on;
> -    else if (cmd == VIRTIO_NET_CTRL_RX_MODE_NOUNI)
> +    } else if (cmd == VIRTIO_NET_CTRL_RX_MODE_NOUNI) {
>          n->nouni = on;
> -    else if (cmd == VIRTIO_NET_CTRL_RX_MODE_NOBCAST)
> +    } else if (cmd == VIRTIO_NET_CTRL_RX_MODE_NOBCAST) {
>          n->nobcast = on;
> -    else
> +    } else {
>          return VIRTIO_NET_ERR;
> +    }
>  
>      return VIRTIO_NET_OK;
>  }
>  
>  static int virtio_net_handle_mac(VirtIONet *n, uint8_t cmd,
> -                                 VirtQueueElement *elem)
> +                                 struct iovec *iov, unsigned int iov_cnt)
>  {
>      struct virtio_net_ctrl_mac mac_data;
> +    size_t s;
>  
> -    if (cmd != VIRTIO_NET_CTRL_MAC_TABLE_SET || elem->out_num != 3 ||
> -        elem->out_sg[1].iov_len < sizeof(mac_data) ||
> -        elem->out_sg[2].iov_len < sizeof(mac_data))
> +    if (cmd != VIRTIO_NET_CTRL_MAC_TABLE_SET) {
>          return VIRTIO_NET_ERR;
> +    }
>  
>      n->mac_table.in_use = 0;
>      n->mac_table.first_multi = 0;
> @@ -360,54 +360,71 @@ static int virtio_net_handle_mac(VirtIONet *n, uint8_t 
> cmd,
>      n->mac_table.multi_overflow = 0;
>      memset(n->mac_table.macs, 0, MAC_TABLE_ENTRIES * ETH_ALEN);
>  
> -    mac_data.entries = ldl_p(elem->out_sg[1].iov_base);
> +    s = iov_to_buf(iov, iov_cnt, 0, &mac_data.entries,
> +                   sizeof(mac_data.entries));
>  
> -    if (sizeof(mac_data.entries) +
> -        (mac_data.entries * ETH_ALEN) > elem->out_sg[1].iov_len)
> +    if (s != sizeof(mac_data.entries)) {
>          return VIRTIO_NET_ERR;
> +    }
> +    iov_discard_front(&iov, &iov_cnt, s);
> +
> +    if (mac_data.entries * ETH_ALEN > iov_size(iov, iov_cnt)) {

The (possible) byteswap was lost.  ldl_p() copies from target endianness
to host endianness.

> +        return VIRTIO_NET_ERR;
> +    }
>  
>      if (mac_data.entries <= MAC_TABLE_ENTRIES) {
> -        memcpy(n->mac_table.macs, elem->out_sg[1].iov_base + 
> sizeof(mac_data),
> -               mac_data.entries * ETH_ALEN);
> +        s = iov_to_buf(iov, iov_cnt, 0, n->mac_table.macs,
> +                       mac_data.entries * ETH_ALEN);
> +        if (s != mac_data.entries * ETH_ALEN) {
> +            return VIRTIO_NET_OK;

s/VIRTIO_NET_OK/VIRTIO_NET_ERR/

> +        }
>          n->mac_table.in_use += mac_data.entries;
>      } else {
>          n->mac_table.uni_overflow = 1;
>      }
>  
> +    iov_discard_front(&iov, &iov_cnt, mac_data.entries * ETH_ALEN);
> +
>      n->mac_table.first_multi = n->mac_table.in_use;
>  
> -    mac_data.entries = ldl_p(elem->out_sg[2].iov_base);
> +    s = iov_to_buf(iov, iov_cnt, 0, &mac_data.entries,
> +                   sizeof(mac_data.entries));

Same deal with mac_data.entries byteswap.

>  
> -    if (sizeof(mac_data.entries) +
> -        (mac_data.entries * ETH_ALEN) > elem->out_sg[2].iov_len)
> +    if (s != sizeof(mac_data.entries)) {
>          return VIRTIO_NET_ERR;
> +    }
>  
> -    if (mac_data.entries) {
> -        if (n->mac_table.in_use + mac_data.entries <= MAC_TABLE_ENTRIES) {
> -            memcpy(n->mac_table.macs + (n->mac_table.in_use * ETH_ALEN),
> -                   elem->out_sg[2].iov_base + sizeof(mac_data),
> -                   mac_data.entries * ETH_ALEN);
> -            n->mac_table.in_use += mac_data.entries;
> -        } else {
> -            n->mac_table.multi_overflow = 1;
> +    iov_discard_front(&iov, &iov_cnt, s);
> +
> +    if (mac_data.entries * ETH_ALEN != iov_size(iov, iov_cnt)) {
> +        return VIRTIO_NET_ERR;
> +    }
> +
> +    if (n->mac_table.in_use + mac_data.entries <= MAC_TABLE_ENTRIES) {
> +        s = iov_to_buf(iov, iov_cnt, 0, n->mac_table.macs,
> +                       mac_data.entries * ETH_ALEN);
> +        if (s != mac_data.entries * ETH_ALEN) {
> +            return VIRTIO_NET_OK;

VIRTIO_NET_ERR

>          }
> +        n->mac_table.in_use += mac_data.entries;
> +    } else {
> +        n->mac_table.multi_overflow = 1;
>      }
>  
>      return VIRTIO_NET_OK;
>  }
>  
>  static int virtio_net_handle_vlan_table(VirtIONet *n, uint8_t cmd,
> -                                        VirtQueueElement *elem)
> +                                        struct iovec *iov, unsigned int 
> iov_cnt)
>  {
>      uint16_t vid;
> +    size_t s;
>  
> -    if (elem->out_num != 2 || elem->out_sg[1].iov_len != sizeof(vid)) {
> -        error_report("virtio-net ctrl invalid vlan command");
> +    s = iov_to_buf(iov, iov_cnt, 0, &vid, sizeof(vid));
> +    if (s != sizeof(vid)) {
>          return VIRTIO_NET_ERR;
>      }
>  
> -    vid = lduw_p(elem->out_sg[1].iov_base);
> -

Byteswap missing.