[Xen-devel] [PATCH net-next 7/7] xen/netback: add fraglist support for to-guest rx

[Paul Durrant <paul.durrant@xxxxxxxxxx>]

From: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>

This allows full 64K skbuffs (with 1500 mtu ethernet, composed of 45
fragments) to be handled by netback for to-guest rx.

Signed-off-by: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
[re-based]
Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
---
Cc: Wei Liu <wei.liu2@xxxxxxxxxx>
---
 drivers/net/xen-netback/interface.c |  2 +-
 drivers/net/xen-netback/rx.c        | 38 ++++++++++++++++++++++++++++---------
 2 files changed, 30 insertions(+), 10 deletions(-)

diff --git a/drivers/net/xen-netback/interface.c 
b/drivers/net/xen-netback/interface.c
index 1a009e7..8fef4fe 100644
--- a/drivers/net/xen-netback/interface.c
+++ b/drivers/net/xen-netback/interface.c
@@ -476,7 +476,7 @@ struct xenvif *xenvif_alloc(struct device *parent, domid_t 
domid,
        dev->netdev_ops = &xenvif_netdev_ops;
        dev->hw_features = NETIF_F_SG |
                NETIF_F_IP_CSUM | NETIF_F_IPV6_CSUM |
-               NETIF_F_TSO | NETIF_F_TSO6;
+               NETIF_F_TSO | NETIF_F_TSO6 | NETIF_F_FRAGLIST;
        dev->features = dev->hw_features | NETIF_F_RXCSUM;
        dev->ethtool_ops = &xenvif_ethtool_ops;
 
diff --git a/drivers/net/xen-netback/rx.c b/drivers/net/xen-netback/rx.c
index 8c8c5b5..8e9ade6 100644
--- a/drivers/net/xen-netback/rx.c
+++ b/drivers/net/xen-netback/rx.c
@@ -215,7 +215,8 @@ static unsigned int xenvif_gso_type(struct sk_buff *skb)
 struct xenvif_pkt_state {
        struct sk_buff *skb;
        size_t remaining_len;
-       int frag; /* frag == -1 => skb->head */
+       struct sk_buff *frag_iter;
+       int frag; /* frag == -1 => frag_iter->head */
        unsigned int frag_offset;
        struct xen_netif_extra_info extras[XEN_NETIF_EXTRA_TYPE_MAX - 1];
        unsigned int extra_count;
@@ -237,6 +238,7 @@ static void xenvif_rx_next_skb(struct xenvif_queue *queue,
        memset(pkt, 0, sizeof(struct xenvif_pkt_state));
 
        pkt->skb = skb;
+       pkt->frag_iter = skb;
        pkt->remaining_len = skb->len;
        pkt->frag = -1;
 
@@ -293,20 +295,40 @@ static void xenvif_rx_complete(struct xenvif_queue *queue,
        __skb_queue_tail(queue->rx_copy.completed, pkt->skb);
 }
 
+static void xenvif_rx_next_frag(struct xenvif_pkt_state *pkt)
+{
+       struct sk_buff *frag_iter = pkt->frag_iter;
+       unsigned int nr_frags = skb_shinfo(frag_iter)->nr_frags;
+
+       pkt->frag++;
+       pkt->frag_offset = 0;
+
+       if (pkt->frag >= nr_frags) {
+               if (frag_iter == pkt->skb)
+                       pkt->frag_iter = skb_shinfo(frag_iter)->frag_list;
+               else
+                       pkt->frag_iter = frag_iter->next;
+
+               pkt->frag = -1;
+       }
+}
+
 static void xenvif_rx_next_chunk(struct xenvif_queue *queue,
                                 struct xenvif_pkt_state *pkt,
                                 unsigned int offset, void **data,
                                 size_t *len)
 {
-       struct sk_buff *skb = pkt->skb;
+       struct sk_buff *frag_iter = pkt->frag_iter;
        void *frag_data;
        size_t frag_len, chunk_len;
 
+       BUG_ON(!frag_iter);
+
        if (pkt->frag == -1) {
-               frag_data = skb->data;
-               frag_len = skb_headlen(skb);
+               frag_data = frag_iter->data;
+               frag_len = skb_headlen(frag_iter);
        } else {
-               skb_frag_t *frag = &skb_shinfo(skb)->frags[pkt->frag];
+               skb_frag_t *frag = &skb_shinfo(frag_iter)->frags[pkt->frag];
 
                frag_data = skb_frag_address(frag);
                frag_len = skb_frag_size(frag);
@@ -322,10 +344,8 @@ static void xenvif_rx_next_chunk(struct xenvif_queue 
*queue,
        pkt->frag_offset += chunk_len;
 
        /* Advance to next frag? */
-       if (frag_len == chunk_len) {
-               pkt->frag++;
-               pkt->frag_offset = 0;
-       }
+       if (frag_len == chunk_len)
+               xenvif_rx_next_frag(pkt);
 
        *data = frag_data;
        *len = chunk_len;
-- 
2.1.4


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