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

Stefan Hajnoczi
2013-01-21T16:03:30Z

On Sat, Jan 19, 2013 at 09:54:26AM +0800, akong@redhat.com wrote:
> From: "Michael S. Tsirkin" <mst@redhat.com>
>
> 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 <mst@redhat.com>
> Signed-off-by: Amos Kong <akong@redhat.com>
> ---
> 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.