Re: [Xen-devel] [PATCH net-next 3/4] xen-netback: pass hash value to the frontend

[Wei Liu]

On Thu, May 05, 2016 at 12:19:29PM +0100, Paul Durrant wrote:
> My recent patch to include/xen/interface/io/netif.h defines a new extra
> info type that can be used to pass hash values between backend and guest
> frontend.
> 
> This patch adds code to xen-netback to pass hash values calculated for
> guest receive-side packets (i.e. netback transmit side) to the frontend.
> 
> Signed-off-by: Paul Durrant 
> Cc: Wei Liu 

Acked-by: Wei Liu 

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[Xen-devel] [PATCH net-next 3/4] xen-netback: pass hash value to the frontend

[Paul Durrant]

My recent patch to include/xen/interface/io/netif.h defines a new extra
info type that can be used to pass hash values between backend and guest
frontend.

This patch adds code to xen-netback to pass hash values calculated for
guest receive-side packets (i.e. netback transmit side) to the frontend.

Signed-off-by: Paul Durrant 
Cc: Wei Liu 
---
 drivers/net/xen-netback/interface.c | 13 ++-
 drivers/net/xen-netback/netback.c   | 78 +++--
 2 files changed, 77 insertions(+), 14 deletions(-)

diff --git a/drivers/net/xen-netback/interface.c 
b/drivers/net/xen-netback/interface.c
index e54b475..b2d945f 100644
--- a/drivers/net/xen-netback/interface.c
+++ b/drivers/net/xen-netback/interface.c
@@ -158,8 +158,17 @@ static u16 xenvif_select_queue(struct net_device *dev, 
struct sk_buff *skb,
struct xenvif *vif = netdev_priv(dev);
unsigned int size = vif->hash.size;
 
-   if (vif->hash.alg == XEN_NETIF_CTRL_HASH_ALGORITHM_NONE)
-   return fallback(dev, skb) % dev->real_num_tx_queues;
+   if (vif->hash.alg == XEN_NETIF_CTRL_HASH_ALGORITHM_NONE) {
+   u16 index = fallback(dev, skb) % dev->real_num_tx_queues;
+
+   /* Make sure there is no hash information in the socket
+* buffer otherwise it would be incorrectly forwarded
+* to the frontend.
+*/
+   skb_clear_hash(skb);
+
+   return index;
+   }
 
xenvif_set_skb_hash(vif, skb);
 
diff --git a/drivers/net/xen-netback/netback.c 
b/drivers/net/xen-netback/netback.c
index 6509d11..7c72510 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -168,6 +168,8 @@ static bool xenvif_rx_ring_slots_available(struct 
xenvif_queue *queue)
needed = DIV_ROUND_UP(skb->len, XEN_PAGE_SIZE);
if (skb_is_gso(skb))
needed++;
+   if (skb->sw_hash)
+   needed++;
 
do {
prod = queue->rx.sring->req_prod;
@@ -285,6 +287,8 @@ struct gop_frag_copy {
struct xenvif_rx_meta *meta;
int head;
int gso_type;
+   int protocol;
+   int hash_present;
 
struct page *page;
 };
@@ -331,8 +335,15 @@ static void xenvif_setup_copy_gop(unsigned long gfn,
npo->copy_off += *len;
info->meta->size += *len;
 
+   if (!info->head)
+   return;
+
/* Leave a gap for the GSO descriptor. */
-   if (info->head && ((1 << info->gso_type) & queue->vif->gso_mask))
+   if ((1 << info->gso_type) & queue->vif->gso_mask)
+   queue->rx.req_cons++;
+
+   /* Leave a gap for the hash extra segment. */
+   if (info->hash_present)
queue->rx.req_cons++;
 
info->head = 0; /* There must be something in this buffer now */
@@ -367,6 +378,11 @@ static void xenvif_gop_frag_copy(struct xenvif_queue 
*queue, struct sk_buff *skb
.npo = npo,
.head = *head,
.gso_type = XEN_NETIF_GSO_TYPE_NONE,
+   /* xenvif_set_skb_hash() will have either set a s/w
+* hash or cleared the hash depending on
+* whether the the frontend wants a hash for this skb.
+*/
+   .hash_present = skb->sw_hash,
};
unsigned long bytes;
 
@@ -555,6 +571,7 @@ void xenvif_kick_thread(struct xenvif_queue *queue)
 
 static void xenvif_rx_action(struct xenvif_queue *queue)
 {
+   struct xenvif *vif = queue->vif;
s8 status;
u16 flags;
struct xen_netif_rx_response *resp;
@@ -590,9 +607,10 @@ static void xenvif_rx_action(struct xenvif_queue *queue)
gnttab_batch_copy(queue->grant_copy_op, npo.copy_prod);
 
while ((skb = __skb_dequeue()) != NULL) {
+   struct xen_netif_extra_info *extra = NULL;
 
if ((1 << queue->meta[npo.meta_cons].gso_type) &
-   queue->vif->gso_prefix_mask) {
+   vif->gso_prefix_mask) {
resp = RING_GET_RESPONSE(>rx,
 queue->rx.rsp_prod_pvt++);
 
@@ -610,7 +628,7 @@ static void xenvif_rx_action(struct xenvif_queue *queue)
queue->stats.tx_bytes += skb->len;
queue->stats.tx_packets++;
 
-   status = xenvif_check_gop(queue->vif,
+   status = xenvif_check_gop(vif,
  XENVIF_RX_CB(skb)->meta_slots_used,
  );
 
@@ -632,21 +650,57 @@ static void xenvif_rx_action(struct xenvif_queue *queue)
flags);
 
if ((1 << queue->meta[npo.meta_cons].gso_type) &
-   queue->vif->gso_mask) {
-   struct xen_netif_extra_info *gso =
-   (struct xen_netif_extra_info *)
+