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[Xen-changelog] [xen-unstable] [NET] front: Transmit SG packets if suppo

To: xen-changelog@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-changelog] [xen-unstable] [NET] front: Transmit SG packets if supported
From: Xen patchbot-unstable <patchbot-unstable@xxxxxxxxxxxxxxxxxxx>
Date: Mon, 05 Jun 2006 18:20:13 +0000
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# HG changeset patch
# User kaf24@xxxxxxxxxxxxxxxxxxxx
# Node ID aecdb4c52fa78dc2824f6be011689a2c4de4de11
# Parent  50db8c95e65d6bf08ba0107399654439ee05b8fc
[NET] front: Transmit SG packets if supported

This patch adds scatter-and-gather transmission support to the frontend.
This allows the MTU to be raised right now and the potential for TSO in
future.

Signed-off-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
---
 linux-2.6-xen-sparse/drivers/xen/netfront/netfront.c |  171 +++++++++++++++----
 xen/include/public/io/ring.h                         |    6 
 2 files changed, 147 insertions(+), 30 deletions(-)

diff -r 50db8c95e65d -r aecdb4c52fa7 
linux-2.6-xen-sparse/drivers/xen/netfront/netfront.c
--- a/linux-2.6-xen-sparse/drivers/xen/netfront/netfront.c      Mon Jun 05 
16:13:47 2006 +0100
+++ b/linux-2.6-xen-sparse/drivers/xen/netfront/netfront.c      Mon Jun 05 
16:33:49 2006 +0100
@@ -45,6 +45,7 @@
 #include <linux/bitops.h>
 #include <linux/ethtool.h>
 #include <linux/in.h>
+#include <linux/if_ether.h>
 #include <net/sock.h>
 #include <net/pkt_sched.h>
 #include <net/arp.h>
@@ -173,6 +174,11 @@ static void xennet_sysfs_delif(struct ne
 #define xennet_sysfs_delif(dev) do { } while(0)
 #endif
 
+static inline int xennet_can_sg(struct net_device *dev)
+{
+       return dev->features & NETIF_F_SG;
+}
+
 /**
  * Entry point to this code when a new device is created.  Allocate the basic
  * structures and the ring buffers for communication with the backend, and
@@ -307,8 +313,6 @@ again:
                goto destroy_ring;
        }
 
-       xenbus_switch_state(dev, XenbusStateConnected);
-
        return 0;
 
  abort_transaction:
@@ -370,12 +374,9 @@ static int setup_device(struct xenbus_de
                goto fail;
 
        memcpy(netdev->dev_addr, info->mac, ETH_ALEN);
-       network_connect(netdev);
        info->irq = bind_evtchn_to_irqhandler(
                info->evtchn, netif_int, SA_SAMPLE_RANDOM, netdev->name,
                netdev);
-       (void)send_fake_arp(netdev);
-       show_device(info);
 
        return 0;
 
@@ -391,15 +392,24 @@ static void backend_changed(struct xenbu
 static void backend_changed(struct xenbus_device *dev,
                            enum xenbus_state backend_state)
 {
+       struct netfront_info *np = dev->data;
+       struct net_device *netdev = np->netdev;
+
        DPRINTK("\n");
 
        switch (backend_state) {
        case XenbusStateInitialising:
-       case XenbusStateInitWait:
        case XenbusStateInitialised:
        case XenbusStateConnected:
        case XenbusStateUnknown:
        case XenbusStateClosed:
+               break;
+
+       case XenbusStateInitWait:
+               network_connect(netdev);
+               xenbus_switch_state(dev, XenbusStateConnected);
+               (void)send_fake_arp(netdev);
+               show_device(np);
                break;
 
        case XenbusStateClosing:
@@ -452,13 +462,17 @@ static int network_open(struct net_devic
        return 0;
 }
 
+static inline int netfront_tx_slot_available(struct netfront_info *np)
+{
+       return RING_FREE_REQUESTS(&np->tx) >= MAX_SKB_FRAGS + 1;
+}
+
 static inline void network_maybe_wake_tx(struct net_device *dev)
 {
        struct netfront_info *np = netdev_priv(dev);
 
        if (unlikely(netif_queue_stopped(dev)) &&
-           !RING_FULL(&np->tx) &&
-           !gnttab_empty_grant_references(&np->gref_tx_head) &&
+           netfront_tx_slot_available(np) &&
            likely(netif_running(dev)))
                netif_wake_queue(dev);
 }
@@ -638,36 +652,95 @@ static void network_alloc_rx_buffers(str
        RING_PUSH_REQUESTS(&np->rx);
 }
 
+static void xennet_make_frags(struct sk_buff *skb, struct net_device *dev,
+                             struct netif_tx_request *tx)
+{
+       struct netfront_info *np = netdev_priv(dev);
+       char *data = skb->data;
+       unsigned long mfn;
+       RING_IDX prod = np->tx.req_prod_pvt;
+       int frags = skb_shinfo(skb)->nr_frags;
+       unsigned int offset = offset_in_page(data);
+       unsigned int len = skb_headlen(skb);
+       unsigned int id;
+       grant_ref_t ref;
+       int i;
+
+       while (len > PAGE_SIZE - offset) {
+               tx->size = PAGE_SIZE - offset;
+               tx->flags |= NETTXF_more_data;
+               len -= tx->size;
+               data += tx->size;
+               offset = 0;
+
+               id = get_id_from_freelist(np->tx_skbs);
+               np->tx_skbs[id] = skb_get(skb);
+               tx = RING_GET_REQUEST(&np->tx, prod++);
+               tx->id = id;
+               ref = gnttab_claim_grant_reference(&np->gref_tx_head);
+               BUG_ON((signed short)ref < 0);
+
+               mfn = virt_to_mfn(data);
+               gnttab_grant_foreign_access_ref(ref, np->xbdev->otherend_id,
+                                               mfn, GNTMAP_readonly);
+
+               tx->gref = np->grant_tx_ref[id] = ref;
+               tx->offset = offset;
+               tx->size = len;
+               tx->flags = 0;
+       }
+
+       for (i = 0; i < frags; i++) {
+               skb_frag_t *frag = skb_shinfo(skb)->frags + i;
+
+               tx->flags |= NETTXF_more_data;
+
+               id = get_id_from_freelist(np->tx_skbs);
+               np->tx_skbs[id] = skb_get(skb);
+               tx = RING_GET_REQUEST(&np->tx, prod++);
+               tx->id = id;
+               ref = gnttab_claim_grant_reference(&np->gref_tx_head);
+               BUG_ON((signed short)ref < 0);
+
+               mfn = pfn_to_mfn(page_to_pfn(frag->page));
+               gnttab_grant_foreign_access_ref(ref, np->xbdev->otherend_id,
+                                               mfn, GNTMAP_readonly);
+
+               tx->gref = np->grant_tx_ref[id] = ref;
+               tx->offset = frag->page_offset;
+               tx->size = frag->size;
+               tx->flags = 0;
+       }
+
+       np->tx.req_prod_pvt = prod;
+}
 
 static int network_start_xmit(struct sk_buff *skb, struct net_device *dev)
 {
        unsigned short id;
        struct netfront_info *np = netdev_priv(dev);
        struct netif_tx_request *tx;
+       char *data = skb->data;
        RING_IDX i;
        grant_ref_t ref;
        unsigned long mfn;
        int notify;
-
-       if (unlikely((((unsigned long)skb->data & ~PAGE_MASK) + skb->len) >=
-                    PAGE_SIZE)) {
-               struct sk_buff *nskb;
-               nskb = __dev_alloc_skb(skb->len, GFP_ATOMIC|__GFP_NOWARN);
-               if (unlikely(nskb == NULL))
-                       goto drop;
-               skb_put(nskb, skb->len);
-               memcpy(nskb->data, skb->data, skb->len);
-               /* Copy only the header fields we use in this driver. */
-               nskb->dev = skb->dev;
-               nskb->ip_summed = skb->ip_summed;
-               nskb->proto_data_valid = skb->proto_data_valid;
-               dev_kfree_skb(skb);
-               skb = nskb;
+       int frags = skb_shinfo(skb)->nr_frags;
+       unsigned int offset = offset_in_page(data);
+       unsigned int len = skb_headlen(skb);
+
+       frags += (offset + len + PAGE_SIZE - 1) / PAGE_SIZE;
+       if (unlikely(frags > MAX_SKB_FRAGS + 1)) {
+               printk(KERN_ALERT "xennet: skb rides the rocket: %d frags\n",
+                      frags);
+               dump_stack();
+               goto drop;
        }
 
        spin_lock_irq(&np->tx_lock);
 
-       if (unlikely(!netif_carrier_ok(dev))) {
+       if (unlikely(!netif_carrier_ok(dev) ||
+                    (frags > 1 && !xennet_can_sg(dev)))) {
                spin_unlock_irq(&np->tx_lock);
                goto drop;
        }
@@ -682,12 +755,12 @@ static int network_start_xmit(struct sk_
        tx->id   = id;
        ref = gnttab_claim_grant_reference(&np->gref_tx_head);
        BUG_ON((signed short)ref < 0);
-       mfn = virt_to_mfn(skb->data);
+       mfn = virt_to_mfn(data);
        gnttab_grant_foreign_access_ref(
                ref, np->xbdev->otherend_id, mfn, GNTMAP_readonly);
        tx->gref = np->grant_tx_ref[id] = ref;
-       tx->offset = (unsigned long)skb->data & ~PAGE_MASK;
-       tx->size = skb->len;
+       tx->offset = offset;
+       tx->size = len;
 
        tx->flags = 0;
        if (skb->ip_summed == CHECKSUM_HW) /* local packet? */
@@ -696,14 +769,17 @@ static int network_start_xmit(struct sk_
                tx->flags |= NETTXF_data_validated;
 
        np->tx.req_prod_pvt = i + 1;
+
+       xennet_make_frags(skb, dev, tx);
+       tx->size = skb->len;
+
        RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&np->tx, notify);
        if (notify)
                notify_remote_via_irq(np->irq);
 
        network_tx_buf_gc(dev);
 
-       if (RING_FULL(&np->tx) ||
-           gnttab_empty_grant_references(&np->gref_tx_head))
+       if (!netfront_tx_slot_available(np))
                netif_stop_queue(dev);
 
        spin_unlock_irq(&np->tx_lock);
@@ -963,12 +1039,46 @@ static struct net_device_stats *network_
        return &np->stats;
 }
 
+static int xennet_change_mtu(struct net_device *dev, int mtu)
+{
+       int max = xennet_can_sg(dev) ? 65535 - ETH_HLEN : ETH_DATA_LEN;
+
+       if (mtu > max)
+               return -EINVAL;
+       dev->mtu = mtu;
+       return 0;
+}
+
+static int xennet_set_sg(struct net_device *dev, u32 data)
+{
+       if (data) {
+               struct netfront_info *np = netdev_priv(dev);
+               int val;
+
+               if (xenbus_scanf(XBT_NULL, np->xbdev->otherend, "feature-sg",
+                                "%d", &val) < 0)
+                       val = 0;
+               if (!val)
+                       return -ENOSYS;
+       } else if (dev->mtu > ETH_DATA_LEN)
+               dev->mtu = ETH_DATA_LEN;
+
+       return ethtool_op_set_sg(dev, data);
+}
+
+static void xennet_set_features(struct net_device *dev)
+{
+       xennet_set_sg(dev, 1);
+}
+
 static void network_connect(struct net_device *dev)
 {
        struct netfront_info *np;
        int i, requeue_idx;
        struct netif_tx_request *tx;
        struct sk_buff *skb;
+
+       xennet_set_features(dev);
 
        np = netdev_priv(dev);
        spin_lock_irq(&np->tx_lock);
@@ -1081,6 +1191,8 @@ static struct ethtool_ops network_ethtoo
 {
        .get_tx_csum = ethtool_op_get_tx_csum,
        .set_tx_csum = ethtool_op_set_tx_csum,
+       .get_sg = ethtool_op_get_sg,
+       .set_sg = xennet_set_sg,
 };
 
 #ifdef CONFIG_SYSFS
@@ -1297,6 +1409,7 @@ static struct net_device * __devinit cre
        netdev->poll            = netif_poll;
        netdev->set_multicast_list = network_set_multicast_list;
        netdev->uninit          = netif_uninit;
+       netdev->change_mtu      = xennet_change_mtu;
        netdev->weight          = 64;
        netdev->features        = NETIF_F_IP_CSUM;
 
diff -r 50db8c95e65d -r aecdb4c52fa7 xen/include/public/io/ring.h
--- a/xen/include/public/io/ring.h      Mon Jun 05 16:13:47 2006 +0100
+++ b/xen/include/public/io/ring.h      Mon Jun 05 16:33:49 2006 +0100
@@ -151,11 +151,15 @@ typedef struct __name##_back_ring __name
 #define RING_SIZE(_r)                                                   \
     ((_r)->nr_ents)
 
+/* Number of free requests (for use on front side only). */
+#define RING_FREE_REQUESTS(_r)                                         \
+    (RING_SIZE(_r) - ((_r)->req_prod_pvt - (_r)->rsp_cons))
+
 /* Test if there is an empty slot available on the front ring.
  * (This is only meaningful from the front. )
  */
 #define RING_FULL(_r)                                                   \
-    (((_r)->req_prod_pvt - (_r)->rsp_cons) == RING_SIZE(_r))
+    (RING_FREE_REQUESTS(_r) == 0)
 
 /* Test if there are outstanding messages to be processed on a ring. */
 #define RING_HAS_UNCONSUMED_RESPONSES(_r)                               \

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