From: t_jeang <devnull@localhost>
Date: Tue, 6 Jan 2009 12:06:01 +0000 (+0000)
Subject: Add support to netback for delivering packets at a certain offset into
X-Git-Tag: blktap2
X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=e0fc7c5daa0f77d9acbc8b438f29008470cb3a40;p=xenclient%2Fkernel.git

Add support to netback for delivering packets at a certain offset into
the page.
---

diff --git a/drivers/xen/netback/common.h b/drivers/xen/netback/common.h
index 10a1d58f..44d1dbf1 100644
--- a/drivers/xen/netback/common.h
+++ b/drivers/xen/netback/common.h
@@ -81,6 +81,7 @@ typedef struct netif_st {
 	/* Internal feature information. */
 	u8 can_queue:1;	/* can queue packets for receiver? */
 	u8 copying_receiver:1;	/* copy packets to receiver?       */
+	unsigned copying_rx_offset;
 
 	/* Allow netif_be_start_xmit() to peek ahead in the rx request ring. */
 	RING_IDX rx_req_cons_peek;
diff --git a/drivers/xen/netback/netback.c b/drivers/xen/netback/netback.c
index d771bf06..526f0fe1 100644
--- a/drivers/xen/netback/netback.c
+++ b/drivers/xen/netback/netback.c
@@ -409,8 +409,13 @@ static u16 netbk_gop_frag(netif_t *netif, struct netbk_rx_meta *meta,
 		}
 		copy_gop->source.offset = offset;
 		copy_gop->dest.domid = netif->domid;
-		copy_gop->dest.offset = 0;
+		if (i == 0)
+			copy_gop->dest.offset = netif->copying_rx_offset;
+		else
+			copy_gop->dest.offset = 0;
 		copy_gop->dest.u.ref = req->gref;
+		/* We rely on Xen to enforce that offset + size <=
+		 * PAGE_SIZE */
 		copy_gop->len = size;
 	} else {
 		meta->copy = 0;
diff --git a/drivers/xen/netback/xenbus.c b/drivers/xen/netback/xenbus.c
index d7faeb62..a7835068 100644
--- a/drivers/xen/netback/xenbus.c
+++ b/drivers/xen/netback/xenbus.c
@@ -104,6 +104,14 @@ static int netback_probe(struct xenbus_device *dev,
 			goto abort_transaction;
 		}
 
+		/* We rx-copy at an offset.. */
+		err = xenbus_printf(xbt, dev->nodename,
+				    "feature-rx-copy-offset", "%d", 1);
+		if (err) {
+			message = "writing feature-rx-copy-offset";
+			goto abort_transaction;
+		}
+
 		/*
 		 * We don't support rx-flip path (except old guests who don't
 		 * grok this feature flag).
@@ -352,7 +360,7 @@ static int connect_rings(struct backend_info *be)
 {
 	struct xenbus_device *dev = be->dev;
 	unsigned long tx_ring_ref, rx_ring_ref;
-	unsigned int evtchn, rx_copy;
+	unsigned int evtchn, rx_copy, rx_copy_offset;
 	int err;
 	int val;
 
@@ -382,6 +390,19 @@ static int connect_rings(struct backend_info *be)
 	}
 	be->netif->copying_receiver = !!rx_copy;
 
+	err = xenbus_scanf(XBT_NIL, dev->otherend, "request-rx-copy-offset",
+			   "%u", &rx_copy_offset);
+	if (err == -ENOENT) {
+		err = 0;
+		rx_copy_offset = 0;
+	}
+	if (err < 0) {
+		xenbus_dev_fatal(dev, err, "reading %s/request-rx-copy-offset",
+				 dev->otherend);
+		return err;
+	}
+	be->netif->copying_rx_offset = rx_copy_offset;
+
 	if (be->netif->dev->tx_queue_len != 0) {
 		if (xenbus_scanf(XBT_NIL, dev->otherend,
 				 "feature-rx-notify", "%d", &val) < 0)