2 files changed, 162 insertions, 20 deletions

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 27559c987d47..e6b5d6ef9ea8 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -34,6 +34,7 @@ module_param(gso, bool, 0444);
 
 /* FIXME: MTU in config. */
 #define MAX_PACKET_LEN (ETH_HLEN+ETH_DATA_LEN)
+#define GOOD_COPY_LEN   128
 
 struct virtnet_info
 {
@@ -58,6 +59,9 @@ struct virtnet_info
         /* I like... big packets and I cannot lie! */
         bool big_packets;
 
+        /* Host will merge rx buffers for big packets (shake it! shake it!) */
+        bool mergeable_rx_bufs;
+
         /* Receive & send queues. */
         struct sk_buff_head recv;
         struct sk_buff_head send;
@@ -66,16 +70,11 @@ struct virtnet_info
         struct page *pages;
 };
 
-static inline struct virtio_net_hdr *skb_vnet_hdr(struct sk_buff *skb)
+static inline void *skb_vnet_hdr(struct sk_buff *skb)
 {
         return (struct virtio_net_hdr *)skb->cb;
 }
 
-static inline void vnet_hdr_to_sg(struct scatterlist *sg, struct sk_buff *skb)
-{
-        sg_init_one(sg, skb_vnet_hdr(skb), sizeof(struct virtio_net_hdr));
-}
-
 static void give_a_page(struct virtnet_info *vi, struct page *page)
 {
         page->private = (unsigned long)vi->pages;
@@ -121,25 +120,97 @@ static void skb_xmit_done(struct virtqueue *svq)
 static void receive_skb(struct net_device *dev, struct sk_buff *skb,
                         unsigned len)
 {
+        struct virtnet_info *vi = netdev_priv(dev);
         struct virtio_net_hdr *hdr = skb_vnet_hdr(skb);
         int err;
+        int i;
 
         if (unlikely(len < sizeof(struct virtio_net_hdr) + ETH_HLEN)) {
                 pr_debug("%s: short packet %i\n", dev->name, len);
                 dev->stats.rx_length_errors++;
                 goto drop;
         }
-        len -= sizeof(struct virtio_net_hdr);
 
-        if (len <= MAX_PACKET_LEN)
-                trim_pages(netdev_priv(dev), skb);
+        if (vi->mergeable_rx_bufs) {
+                struct virtio_net_hdr_mrg_rxbuf *mhdr = skb_vnet_hdr(skb);
+                unsigned int copy;
+                char *p = page_address(skb_shinfo(skb)->frags[0].page);
 
-        err = pskb_trim(skb, len);
-        if (err) {
-                pr_debug("%s: pskb_trim failed %i %d\n", dev->name, len, err);
-                dev->stats.rx_dropped++;
-                goto drop;
+                if (len > PAGE_SIZE)
+                        len = PAGE_SIZE;
+                len -= sizeof(struct virtio_net_hdr_mrg_rxbuf);
+
+                memcpy(hdr, p, sizeof(*mhdr));
+                p += sizeof(*mhdr);
+
+                copy = len;
+                if (copy > skb_tailroom(skb))
+                        copy = skb_tailroom(skb);
+
+                memcpy(skb_put(skb, copy), p, copy);
+
+                len -= copy;
+
+                if (!len) {
+                        give_a_page(vi, skb_shinfo(skb)->frags[0].page);
+                        skb_shinfo(skb)->nr_frags--;
+                } else {
+                        skb_shinfo(skb)->frags[0].page_offset +=
+                                sizeof(*mhdr) + copy;
+                        skb_shinfo(skb)->frags[0].size = len;
+                        skb->data_len += len;
+                        skb->len += len;
+                }
+
+                while (--mhdr->num_buffers) {
+                        struct sk_buff *nskb;
+
+                        i = skb_shinfo(skb)->nr_frags;
+                        if (i >= MAX_SKB_FRAGS) {
+                                pr_debug("%s: packet too long %d\n", dev->name,
+                                         len);
+                                dev->stats.rx_length_errors++;
+                                goto drop;
+                        }
+
+                        nskb = vi->rvq->vq_ops->get_buf(vi->rvq, &len);
+                        if (!nskb) {
+                                pr_debug("%s: rx error: %d buffers missing\n",
+                                         dev->name, mhdr->num_buffers);
+                                dev->stats.rx_length_errors++;
+                                goto drop;
+                        }
+
+                        __skb_unlink(nskb, &vi->recv);
+                        vi->num--;
+
+                        skb_shinfo(skb)->frags[i] = skb_shinfo(nskb)->frags[0];
+                        skb_shinfo(nskb)->nr_frags = 0;
+                        kfree_skb(nskb);
+
+                        if (len > PAGE_SIZE)
+                                len = PAGE_SIZE;
+
+                        skb_shinfo(skb)->frags[i].size = len;
+                        skb_shinfo(skb)->nr_frags++;
+                        skb->data_len += len;
+                        skb->len += len;
+                }
+        } else {
+                len -= sizeof(struct virtio_net_hdr);
+
+                if (len <= MAX_PACKET_LEN)
+                        trim_pages(vi, skb);
+
+                err = pskb_trim(skb, len);
+                if (err) {
+                        pr_debug("%s: pskb_trim failed %i %d\n", dev->name,
+                                 len, err);
+                        dev->stats.rx_dropped++;
+                        goto drop;
+                }
         }
+
         skb->truesize += skb->data_len;
         dev->stats.rx_bytes += skb->len;
         dev->stats.rx_packets++;
@@ -198,7 +269,7 @@ drop:
         dev_kfree_skb(skb);
 }
 
-static void try_fill_recv(struct virtnet_info *vi)
+static void try_fill_recv_maxbufs(struct virtnet_info *vi)
 {
         struct sk_buff *skb;
         struct scatterlist sg[2+MAX_SKB_FRAGS];
@@ -206,12 +277,16 @@ static void try_fill_recv(struct virtnet_info *vi)
 
         sg_init_table(sg, 2+MAX_SKB_FRAGS);
         for (;;) {
+                struct virtio_net_hdr *hdr;
+
                 skb = netdev_alloc_skb(vi->dev, MAX_PACKET_LEN);
                 if (unlikely(!skb))
                         break;
 
                 skb_put(skb, MAX_PACKET_LEN);
-                vnet_hdr_to_sg(sg, skb);
+
+                hdr = skb_vnet_hdr(skb);
+                sg_init_one(sg, hdr, sizeof(*hdr));
 
                 if (vi->big_packets) {
                         for (i = 0; i < MAX_SKB_FRAGS; i++) {
@@ -247,6 +322,54 @@ static void try_fill_recv(struct virtnet_info *vi)
         vi->rvq->vq_ops->kick(vi->rvq);
 }
 
+static void try_fill_recv(struct virtnet_info *vi)
+{
+        struct sk_buff *skb;
+        struct scatterlist sg[1];
+        int err;
+
+        if (!vi->mergeable_rx_bufs) {
+                try_fill_recv_maxbufs(vi);
+                return;
+        }
+
+        for (;;) {
+                skb_frag_t *f;
+
+                skb = netdev_alloc_skb(vi->dev, GOOD_COPY_LEN + NET_IP_ALIGN);
+                if (unlikely(!skb))
+                        break;
+
+                skb_reserve(skb, NET_IP_ALIGN);
+
+                f = &skb_shinfo(skb)->frags[0];
+                f->page = get_a_page(vi, GFP_ATOMIC);
+                if (!f->page) {
+                        kfree_skb(skb);
+                        break;
+                }
+
+                f->page_offset = 0;
+                f->size = PAGE_SIZE;
+
+                skb_shinfo(skb)->nr_frags++;
+
+                sg_init_one(sg, page_address(f->page), PAGE_SIZE);
+                skb_queue_head(&vi->recv, skb);
+
+                err = vi->rvq->vq_ops->add_buf(vi->rvq, sg, 0, 1, skb);
+                if (err) {
+                        skb_unlink(skb, &vi->recv);
+                        kfree_skb(skb);
+                        break;
+                }
+                vi->num++;
+        }
+        if (unlikely(vi->num > vi->max))
+                vi->max = vi->num;
+        vi->rvq->vq_ops->kick(vi->rvq);
+}
+
 static void skb_recv_done(struct virtqueue *rvq)
 {
         struct virtnet_info *vi = rvq->vdev->priv;
@@ -325,15 +448,14 @@ static int xmit_skb(struct virtnet_info *vi, struct sk_buff *skb)
 {
         int num, err;
         struct scatterlist sg[2+MAX_SKB_FRAGS];
-        struct virtio_net_hdr *hdr;
+        struct virtio_net_hdr_mrg_rxbuf *mhdr = skb_vnet_hdr(skb);
+        struct virtio_net_hdr *hdr = skb_vnet_hdr(skb);
         const unsigned char *dest = ((struct ethhdr *)skb->data)->h_dest;
 
         sg_init_table(sg, 2+MAX_SKB_FRAGS);
 
         pr_debug("%s: xmit %p %pM\n", vi->dev->name, skb, dest);
 
-        /* Encode metadata header at front. */
-        hdr = skb_vnet_hdr(skb);
         if (skb->ip_summed == CHECKSUM_PARTIAL) {
                 hdr->flags = VIRTIO_NET_HDR_F_NEEDS_CSUM;
                 hdr->csum_start = skb->csum_start - skb_headroom(skb);
@@ -361,7 +483,14 @@ static int xmit_skb(struct virtnet_info *vi, struct sk_buff *skb)
                 hdr->gso_size = hdr->hdr_len = 0;
         }
 
-        vnet_hdr_to_sg(sg, skb);
+        mhdr->num_buffers = 0;
+
+        /* Encode metadata header at front. */
+        if (vi->mergeable_rx_bufs)
+                sg_init_one(sg, mhdr, sizeof(*mhdr));
+        else
+                sg_init_one(sg, hdr, sizeof(*hdr));
+
         num = skb_to_sgvec(skb, sg+1, 0, skb->len) + 1;
 
         err = vi->svq->vq_ops->add_buf(vi->svq, sg, num, 0, skb);
@@ -551,6 +680,9 @@ static int virtnet_probe(struct virtio_device *vdev)
             || virtio_has_feature(vdev, VIRTIO_NET_F_GUEST_ECN))
                 vi->big_packets = true;
 
+        if (virtio_has_feature(vdev, VIRTIO_NET_F_MRG_RXBUF))
+                vi->mergeable_rx_bufs = true;
+
         /* We expect two virtqueues, receive then send. */
         vi->rvq = vdev->config->find_vq(vdev, 0, skb_recv_done);
         if (IS_ERR(vi->rvq)) {
@@ -643,6 +775,7 @@ static unsigned int features[] = {
         VIRTIO_NET_F_HOST_TSO4, VIRTIO_NET_F_HOST_UFO, VIRTIO_NET_F_HOST_TSO6,
         VIRTIO_NET_F_HOST_ECN, VIRTIO_NET_F_GUEST_TSO4, VIRTIO_NET_F_GUEST_TSO6,
         VIRTIO_NET_F_GUEST_ECN, /* We don't yet handle UFO input. */
+        VIRTIO_NET_F_MRG_RXBUF,
         VIRTIO_F_NOTIFY_ON_EMPTY,
 };
 
diff --git a/include/linux/virtio_net.h b/include/linux/virtio_net.h
index 5e33761b9b8a..5cdd0aa8bde9 100644
--- a/include/linux/virtio_net.h
+++ b/include/linux/virtio_net.h
@@ -20,6 +20,7 @@
 #define VIRTIO_NET_F_HOST_TSO6  12      /* Host can handle TSOv6 in. */
 #define VIRTIO_NET_F_HOST_ECN   13      /* Host can handle TSO[6] w/ ECN in. */
 #define VIRTIO_NET_F_HOST_UFO   14      /* Host can handle UFO in. */
+#define VIRTIO_NET_F_MRG_RXBUF  15      /* Host can merge receive buffers. */
 
 struct virtio_net_config
 {
@@ -44,4 +45,12 @@ struct virtio_net_hdr
         __u16 csum_start;       /* Position to start checksumming from */
         __u16 csum_offset;      /* Offset after that to place checksum */
 };
+
+/* This is the version of the header to use when the MRG_RXBUF
+ * feature has been negotiated. */
+struct virtio_net_hdr_mrg_rxbuf {
+        struct virtio_net_hdr hdr;
+        __u16 num_buffers;      /* Number of merged rx buffers */
+};
+
 #endif /* _LINUX_VIRTIO_NET_H */