virtio_net: get rid of virtio_net_hdr/skb_vnet_hdr

virtio 1.0 doesn't use virtio_net_hdr anymore, and in fact, it's not
really useful since virtio_net_hdr_mrg_rxbuf includes that as the first
field anyway.

Let's drop it, precalculate header len and store within vi instead.

This way we can also remove struct skb_vnet_hdr.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Reviewed-by: Jason Wang <jasowang@redhat.com>

1 files changed, 41 insertions, 49 deletions

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 1630c217d9f7..516f2cb034b5 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -123,6 +123,9 @@ struct virtnet_info {
         /* Host can handle any s/g split between our header and packet data */
         bool any_header_sg;
 
+        /* Packet virtio header size */
+        u8 hdr_len;
+
         /* Active statistics */
         struct virtnet_stats __percpu *stats;
 
@@ -139,21 +142,14 @@ struct virtnet_info {
         struct notifier_block nb;
 };
 
-struct skb_vnet_hdr {
-        union {
-                struct virtio_net_hdr hdr;
-                struct virtio_net_hdr_mrg_rxbuf mhdr;
-        };
-};
-
 struct padded_vnet_hdr {
-        struct virtio_net_hdr hdr;
+        struct virtio_net_hdr_mrg_rxbuf hdr;
         /*
-         * virtio_net_hdr should be in a separated sg buffer because of a
-         * QEMU bug, and data sg buffer shares same page with this header sg.
-         * This padding makes next sg 16 byte aligned after virtio_net_hdr.
+         * hdr is in a separate sg buffer, and data sg buffer shares same page
+         * with this header sg. This padding makes next sg 16 byte aligned
+         * after the header.
          */
-        char padding[6];
+        char padding[4];
 };
 
 /* Converting between virtqueue no. and kernel tx/rx queue no.
@@ -179,9 +175,9 @@ static int rxq2vq(int rxq)
         return rxq * 2;
 }
 
-static inline struct skb_vnet_hdr *skb_vnet_hdr(struct sk_buff *skb)
+static inline struct virtio_net_hdr_mrg_rxbuf *skb_vnet_hdr(struct sk_buff *skb)
 {
-        return (struct skb_vnet_hdr *)skb->cb;
+        return (struct virtio_net_hdr_mrg_rxbuf *)skb->cb;
 }
 
 /*
@@ -247,7 +243,7 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi,
                                    unsigned int len, unsigned int truesize)
 {
         struct sk_buff *skb;
-        struct skb_vnet_hdr *hdr;
+        struct virtio_net_hdr_mrg_rxbuf *hdr;
         unsigned int copy, hdr_len, hdr_padded_len;
         char *p;
 
@@ -260,13 +256,11 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi,
 
         hdr = skb_vnet_hdr(skb);
 
-        if (vi->mergeable_rx_bufs) {
-                hdr_len = sizeof hdr->mhdr;
-                hdr_padded_len = sizeof hdr->mhdr;
-        } else {
-                hdr_len = sizeof hdr->hdr;
+        hdr_len = vi->hdr_len;
+        if (vi->mergeable_rx_bufs)
+                hdr_padded_len = sizeof *hdr;
+        else
                 hdr_padded_len = sizeof(struct padded_vnet_hdr);
-        }
 
         memcpy(hdr, p, hdr_len);
 
@@ -317,11 +311,11 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi,
         return skb;
 }
 
-static struct sk_buff *receive_small(void *buf, unsigned int len)
+static struct sk_buff *receive_small(struct virtnet_info *vi, void *buf, unsigned int len)
 {
         struct sk_buff * skb = buf;
 
-        len -= sizeof(struct virtio_net_hdr);
+        len -= vi->hdr_len;
         skb_trim(skb, len);
 
         return skb;
@@ -354,8 +348,8 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
                                          unsigned int len)
 {
         void *buf = mergeable_ctx_to_buf_address(ctx);
-        struct skb_vnet_hdr *hdr = buf;
-        u16 num_buf = virtio16_to_cpu(rq->vq->vdev, hdr->mhdr.num_buffers);
+        struct virtio_net_hdr_mrg_rxbuf *hdr = buf;
+        u16 num_buf = virtio16_to_cpu(vi->vdev, hdr->num_buffers);
         struct page *page = virt_to_head_page(buf);
         int offset = buf - page_address(page);
         unsigned int truesize = max(len, mergeable_ctx_to_buf_truesize(ctx));
@@ -373,8 +367,8 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
                 if (unlikely(!ctx)) {
                         pr_debug("%s: rx error: %d buffers out of %d missing\n",
                                  dev->name, num_buf,
-                                 virtio16_to_cpu(rq->vq->vdev,
-                                                 hdr->mhdr.num_buffers));
+                                 virtio16_to_cpu(vi->vdev,
+                                                 hdr->num_buffers));
                         dev->stats.rx_length_errors++;
                         goto err_buf;
                 }
@@ -441,7 +435,7 @@ static void receive_buf(struct virtnet_info *vi, struct receive_queue *rq,
         struct net_device *dev = vi->dev;
         struct virtnet_stats *stats = this_cpu_ptr(vi->stats);
         struct sk_buff *skb;
-        struct skb_vnet_hdr *hdr;
+        struct virtio_net_hdr_mrg_rxbuf *hdr;
 
         if (unlikely(len < sizeof(struct virtio_net_hdr) + ETH_HLEN)) {
                 pr_debug("%s: short packet %i\n", dev->name, len);
@@ -463,7 +457,7 @@ static void receive_buf(struct virtnet_info *vi, struct receive_queue *rq,
         else if (vi->big_packets)
                 skb = receive_big(dev, vi, rq, buf, len);
         else
-                skb = receive_small(buf, len);
+                skb = receive_small(vi, buf, len);
 
         if (unlikely(!skb))
                 return;
@@ -545,7 +539,7 @@ static int add_recvbuf_small(struct virtnet_info *vi, struct receive_queue *rq,
                              gfp_t gfp)
 {
         struct sk_buff *skb;
-        struct skb_vnet_hdr *hdr;
+        struct virtio_net_hdr_mrg_rxbuf *hdr;
         int err;
 
         skb = __netdev_alloc_skb_ip_align(vi->dev, GOOD_PACKET_LEN, gfp);
@@ -556,7 +550,7 @@ static int add_recvbuf_small(struct virtnet_info *vi, struct receive_queue *rq,
 
         hdr = skb_vnet_hdr(skb);
         sg_init_table(rq->sg, MAX_SKB_FRAGS + 2);
-        sg_set_buf(rq->sg, &hdr->hdr, sizeof hdr->hdr);
+        sg_set_buf(rq->sg, hdr, vi->hdr_len);
         skb_to_sgvec(skb, rq->sg + 1, 0, skb->len);
 
         err = virtqueue_add_inbuf(rq->vq, rq->sg, 2, skb, gfp);
@@ -566,7 +560,8 @@ static int add_recvbuf_small(struct virtnet_info *vi, struct receive_queue *rq,
         return err;
 }
 
-static int add_recvbuf_big(struct receive_queue *rq, gfp_t gfp)
+static int add_recvbuf_big(struct virtnet_info *vi, struct receive_queue *rq,
+                           gfp_t gfp)
 {
         struct page *first, *list = NULL;
         char *p;
@@ -597,8 +592,8 @@ static int add_recvbuf_big(struct receive_queue *rq, gfp_t gfp)
         p = page_address(first);
 
         /* rq->sg[0], rq->sg[1] share the same page */
-        /* a separated rq->sg[0] for virtio_net_hdr only due to QEMU bug */
-        sg_set_buf(&rq->sg[0], p, sizeof(struct virtio_net_hdr));
+        /* a separated rq->sg[0] for header - required in case !any_header_sg */
+        sg_set_buf(&rq->sg[0], p, vi->hdr_len);
 
         /* rq->sg[1] for data packet, from offset */
         offset = sizeof(struct padded_vnet_hdr);
@@ -677,7 +672,7 @@ static bool try_fill_recv(struct virtnet_info *vi, struct receive_queue *rq,
                 if (vi->mergeable_rx_bufs)
                         err = add_recvbuf_mergeable(rq, gfp);
                 else if (vi->big_packets)
-                        err = add_recvbuf_big(rq, gfp);
+                        err = add_recvbuf_big(vi, rq, gfp);
                 else
                         err = add_recvbuf_small(vi, rq, gfp);
 
@@ -857,18 +852,14 @@ static void free_old_xmit_skbs(struct send_queue *sq)
 
 static int xmit_skb(struct send_queue *sq, struct sk_buff *skb)
 {
-        struct skb_vnet_hdr *hdr;
+        struct virtio_net_hdr_mrg_rxbuf *hdr;
         const unsigned char *dest = ((struct ethhdr *)skb->data)->h_dest;
         struct virtnet_info *vi = sq->vq->vdev->priv;
         unsigned num_sg;
-        unsigned hdr_len;
+        unsigned hdr_len = vi->hdr_len;
         bool can_push;
 
         pr_debug("%s: xmit %p %pM\n", vi->dev->name, skb, dest);
-        if (vi->mergeable_rx_bufs)
-                hdr_len = sizeof hdr->mhdr;
-        else
-                hdr_len = sizeof hdr->hdr;
 
         can_push = vi->any_header_sg &&
                 !((unsigned long)skb->data & (__alignof__(*hdr) - 1)) &&
@@ -876,7 +867,7 @@ static int xmit_skb(struct send_queue *sq, struct sk_buff *skb)
         /* Even if we can, don't push here yet as this would skew
          * csum_start offset below. */
         if (can_push)
-                hdr = (struct skb_vnet_hdr *)(skb->data - hdr_len);
+                hdr = (struct virtio_net_hdr_mrg_rxbuf *)(skb->data - hdr_len);
         else
                 hdr = skb_vnet_hdr(skb);
 
@@ -909,7 +900,7 @@ static int xmit_skb(struct send_queue *sq, struct sk_buff *skb)
         }
 
         if (vi->mergeable_rx_bufs)
-                hdr->mhdr.num_buffers = 0;
+                hdr->num_buffers = 0;
 
         sg_init_table(sq->sg, MAX_SKB_FRAGS + 2);
         if (can_push) {
@@ -1814,18 +1805,19 @@ static int virtnet_probe(struct virtio_device *vdev)
         if (virtio_has_feature(vdev, VIRTIO_NET_F_MRG_RXBUF))
                 vi->mergeable_rx_bufs = true;
 
+        if (virtio_has_feature(vdev, VIRTIO_NET_F_MRG_RXBUF))
+                vi->hdr_len = sizeof(struct virtio_net_hdr_mrg_rxbuf);
+        else
+                vi->hdr_len = sizeof(struct virtio_net_hdr);
+
         if (virtio_has_feature(vdev, VIRTIO_F_ANY_LAYOUT))
                 vi->any_header_sg = true;
 
         if (virtio_has_feature(vdev, VIRTIO_NET_F_CTRL_VQ))
                 vi->has_cvq = true;
 
-        if (vi->any_header_sg) {
-                if (vi->mergeable_rx_bufs)
-                        dev->needed_headroom = sizeof(struct virtio_net_hdr_mrg_rxbuf);
-                else
-                        dev->needed_headroom = sizeof(struct virtio_net_hdr);
-        }
+        if (vi->any_header_sg)
+                dev->needed_headroom = vi->hdr_len;
 
         /* Use single tx/rx queue pair as default */
         vi->curr_queue_pairs = 1;