[PATCH net-next v2 1/2] xen-netback: Rename map ops

[PATCH net-next v2 1/2] xen-netback: Rename map ops

[Zoltan Kiss]

Rename identifiers to state explicitly that they refer to map ops.

Signed-off-by: Zoltan Kiss <zoltan.kiss@citrix.com>
---
diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index 0efa32d..a650899 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -915,9 +915,9 @@ static inline void xenvif_grant_handle_reset(struct xenvif *vif,
 
 static int xenvif_tx_check_gop(struct xenvif *vif,
 			       struct sk_buff *skb,
-			       struct gnttab_map_grant_ref **gopp)
+			       struct gnttab_map_grant_ref **gopp_map)
 {
-	struct gnttab_map_grant_ref *gop = *gopp;
+	struct gnttab_map_grant_ref *gop_map = *gopp_map;
 	u16 pending_idx = XENVIF_TX_CB(skb)->pending_idx;
 	struct skb_shared_info *shinfo = skb_shinfo(skb);
 	struct pending_tx_info *tx_info;
@@ -926,11 +926,11 @@ static int xenvif_tx_check_gop(struct xenvif *vif,
 	struct sk_buff *first_skb = NULL;
 
 	/* Check status of header. */
-	err = gop->status;
+	err = gop_map->status;
 	if (unlikely(err))
 		xenvif_idx_release(vif, pending_idx, XEN_NETIF_RSP_ERROR);
 	else
-		xenvif_grant_handle_set(vif, pending_idx , gop->handle);
+		xenvif_grant_handle_set(vif, pending_idx , gop_map->handle);
 
 	/* Skip first skb fragment if it is on same page as header fragment. */
 	start = (frag_get_pending_idx(&shinfo->frags[0]) == pending_idx);
@@ -943,10 +943,12 @@ check_frags:
 		tx_info = &vif->pending_tx_info[pending_idx];
 
 		/* Check error status: if okay then remember grant handle. */
-		newerr = (++gop)->status;
+		newerr = (++gop_map)->status;
 
 		if (likely(!newerr)) {
-			xenvif_grant_handle_set(vif, pending_idx , gop->handle);
+			xenvif_grant_handle_set(vif,
+						pending_idx,
+						gop_map->handle);
 			/* Had a previous error? Invalidate this fragment. */
 			if (unlikely(err))
 				xenvif_idx_unmap(vif, pending_idx);
@@ -998,7 +1000,7 @@ check_frags:
 		}
 	}
 
-	*gopp = gop + 1;
+	*gopp_map = gop_map + 1;
 	return err;
 }
 
@@ -1374,7 +1376,7 @@ static int xenvif_handle_frag_list(struct xenvif *vif, struct sk_buff *skb)
 
 static int xenvif_tx_submit(struct xenvif *vif)
 {
-	struct gnttab_map_grant_ref *gop = vif->tx_map_ops;
+	struct gnttab_map_grant_ref *gop_map = vif->tx_map_ops;
 	struct sk_buff *skb;
 	int work_done = 0;
 
@@ -1387,7 +1389,7 @@ static int xenvif_tx_submit(struct xenvif *vif)
 		txp = &vif->pending_tx_info[pending_idx].req;
 
 		/* Check the remap error code. */
-		if (unlikely(xenvif_tx_check_gop(vif, skb, &gop))) {
+		if (unlikely(xenvif_tx_check_gop(vif, skb, &gop_map))) {
 			netdev_dbg(vif->dev, "netback grant failed.\n");
 			skb_shinfo(skb)->nr_frags = 0;
 			kfree_skb(skb);
@@ -1586,21 +1588,21 @@ static inline void xenvif_tx_dealloc_action(struct xenvif *vif)
 /* Called after netfront has transmitted */
 int xenvif_tx_action(struct xenvif *vif, int budget)
 {
-	unsigned nr_gops;
+	unsigned nr_mops;
 	int work_done, ret;
 
 	if (unlikely(!tx_work_todo(vif)))
 		return 0;
 
-	nr_gops = xenvif_tx_build_gops(vif, budget);
+	nr_mops = xenvif_tx_build_gops(vif, budget);
 
-	if (nr_gops == 0)
+	if (nr_mops == 0)
 		return 0;
 
 	ret = gnttab_map_refs(vif->tx_map_ops,
 			      NULL,
 			      vif->pages_to_map,
-			      nr_gops);
+			      nr_mops);
 	BUG_ON(ret);
 
 	work_done = xenvif_tx_submit(vif);

[PATCH net-next v2 2/2] xen-netback: Grant copy the header instead of map and memcpy

[Zoltan Kiss]

An old inefficiency of the TX path that we are grant mapping the first slot,
and then copy the header part to the linear area. Instead, doing a grant copy
for that header straight on is more reasonable. Especially because there are
ongoing efforts to make Xen avoiding TLB flush after unmap when the page were
not touched in Dom0. In the original way the memcpy ruined that.
The key changes:
- the vif has a tx_copy_ops array again
- xenvif_tx_build_gops sets up the grant copy operations
- we don't have to figure out whether the header and first frag are on the same
  grant mapped page or not
Note, we only grant copy PKT_PROT_LEN bytes from the first slot, the rest (if
any) will be on the first frag, which is grant mapped. If the first slot is
smaller than PKT_PROT_LEN, then we grant copy that, and later __pskb_pull_tail
will pull more from the frags (if any)

Unrelated, but I've made a small refactoring in xenvif_get_extras as well.

Signed-off-by: Zoltan Kiss <zoltan.kiss@citrix.com>
---
v2:
- extend commit message
- add patch to rename map ops

diff --git a/drivers/net/xen-netback/common.h b/drivers/net/xen-netback/common.h
index 89b2d42..c995532 100644
--- a/drivers/net/xen-netback/common.h
+++ b/drivers/net/xen-netback/common.h
@@ -119,6 +119,7 @@ struct xenvif {
 	struct pending_tx_info pending_tx_info[MAX_PENDING_REQS];
 	grant_handle_t grant_tx_handle[MAX_PENDING_REQS];
 
+	struct gnttab_copy tx_copy_ops[MAX_PENDING_REQS];
 	struct gnttab_map_grant_ref tx_map_ops[MAX_PENDING_REQS];
 	struct gnttab_unmap_grant_ref tx_unmap_ops[MAX_PENDING_REQS];
 	/* passed to gnttab_[un]map_refs with pages under (un)mapping */
diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index e781366..ba11ff5 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -915,35 +915,30 @@ static inline void xenvif_grant_handle_reset(struct xenvif *vif,
 
 static int xenvif_tx_check_gop(struct xenvif *vif,
 			       struct sk_buff *skb,
-			       struct gnttab_map_grant_ref **gopp_map)
+			       struct gnttab_map_grant_ref **gopp_map,
+			       struct gnttab_copy **gopp_copy)
 {
 	struct gnttab_map_grant_ref *gop_map = *gopp_map;
 	u16 pending_idx = XENVIF_TX_CB(skb)->pending_idx;
 	struct skb_shared_info *shinfo = skb_shinfo(skb);
-	struct pending_tx_info *tx_info;
 	int nr_frags = shinfo->nr_frags;
-	int i, err, start;
+	int i, err;
 	struct sk_buff *first_skb = NULL;
 
 	/* Check status of header. */
-	err = gop_map->status;
+	err = (*gopp_copy)->status;
+	(*gopp_copy)++;
 	if (unlikely(err))
 		xenvif_idx_release(vif, pending_idx, XEN_NETIF_RSP_ERROR);
-	else
-		xenvif_grant_handle_set(vif, pending_idx , gop_map->handle);
-
-	/* Skip first skb fragment if it is on same page as header fragment. */
-	start = (frag_get_pending_idx(&shinfo->frags[0]) == pending_idx);
 
 check_frags:
-	for (i = start; i < nr_frags; i++) {
+	for (i = 0; i < nr_frags; i++, gop_map++) {
 		int j, newerr;
 
 		pending_idx = frag_get_pending_idx(&shinfo->frags[i]);
-		tx_info = &vif->pending_tx_info[pending_idx];
 
 		/* Check error status: if okay then remember grant handle. */
-		newerr = (++gop_map)->status;
+		newerr = (gop_map)->status;
 
 		if (likely(!newerr)) {
 			xenvif_grant_handle_set(vif,
@@ -961,13 +956,8 @@ check_frags:
 		/* Not the first error? Preceding frags already invalidated. */
 		if (err)
 			continue;
-		/* First error: invalidate header and preceding fragments. */
-		if (!first_skb)
-			pending_idx = XENVIF_TX_CB(skb)->pending_idx;
-		else
-			pending_idx = XENVIF_TX_CB(skb)->pending_idx;
-		xenvif_idx_unmap(vif, pending_idx);
-		for (j = start; j < i; j++) {
+		/* First error: invalidate preceding fragments. */
+		for (j = 0; j < i; j++) {
 			pending_idx = frag_get_pending_idx(&shinfo->frags[j]);
 			xenvif_idx_unmap(vif, pending_idx);
 		}
@@ -981,7 +971,6 @@ check_frags:
 		skb = shinfo->frag_list;
 		shinfo = skb_shinfo(skb);
 		nr_frags = shinfo->nr_frags;
-		start = 0;
 
 		goto check_frags;
 	}
@@ -992,15 +981,13 @@ check_frags:
 	if (first_skb && err) {
 		int j;
 		shinfo = skb_shinfo(first_skb);
-		pending_idx = XENVIF_TX_CB(skb)->pending_idx;
-		start = (frag_get_pending_idx(&shinfo->frags[0]) == pending_idx);
-		for (j = start; j < shinfo->nr_frags; j++) {
+		for (j = 0; j < shinfo->nr_frags; j++) {
 			pending_idx = frag_get_pending_idx(&shinfo->frags[j]);
 			xenvif_idx_unmap(vif, pending_idx);
 		}
 	}
 
-	*gopp_map = gop_map + 1;
+	*gopp_map = gop_map;
 	return err;
 }
 
@@ -1011,9 +998,6 @@ static void xenvif_fill_frags(struct xenvif *vif, struct sk_buff *skb)
 	int i;
 	u16 prev_pending_idx = INVALID_PENDING_IDX;
 
-	if (skb_shinfo(skb)->destructor_arg)
-		prev_pending_idx = XENVIF_TX_CB(skb)->pending_idx;
-
 	for (i = 0; i < nr_frags; i++) {
 		skb_frag_t *frag = shinfo->frags + i;
 		struct xen_netif_tx_request *txp;
@@ -1023,10 +1007,10 @@ static void xenvif_fill_frags(struct xenvif *vif, struct sk_buff *skb)
 		pending_idx = frag_get_pending_idx(frag);
 
 		/* If this is not the first frag, chain it to the previous*/
-		if (unlikely(prev_pending_idx == INVALID_PENDING_IDX))
+		if (prev_pending_idx == INVALID_PENDING_IDX)
 			skb_shinfo(skb)->destructor_arg =
 				&callback_param(vif, pending_idx);
-		else if (likely(pending_idx != prev_pending_idx))
+		else
 			callback_param(vif, prev_pending_idx).ctx =
 				&callback_param(vif, pending_idx);
 
@@ -1067,9 +1051,9 @@ static int xenvif_get_extras(struct xenvif *vif,
 
 		memcpy(&extra, RING_GET_REQUEST(&vif->tx, cons),
 		       sizeof(extra));
+		vif->tx.req_cons = ++cons;
 		if (unlikely(!extra.type ||
 			     extra.type >= XEN_NETIF_EXTRA_TYPE_MAX)) {
-			vif->tx.req_cons = ++cons;
 			netdev_err(vif->dev,
 				   "Invalid extra type: %d\n", extra.type);
 			xenvif_fatal_tx_err(vif);
@@ -1077,7 +1061,6 @@ static int xenvif_get_extras(struct xenvif *vif,
 		}
 
 		memcpy(&extras[extra.type - 1], &extra, sizeof(extra));
-		vif->tx.req_cons = ++cons;
 	} while (extra.flags & XEN_NETIF_EXTRA_FLAG_MORE);
 
 	return work_to_do;
@@ -1166,7 +1149,10 @@ static bool tx_credit_exceeded(struct xenvif *vif, unsigned size)
 	return false;
 }
 
-static unsigned xenvif_tx_build_gops(struct xenvif *vif, int budget)
+static void xenvif_tx_build_gops(struct xenvif *vif,
+				     int budget,
+				     unsigned *copy_ops,
+				     unsigned *map_ops)
 {
 	struct gnttab_map_grant_ref *gop = vif->tx_map_ops, *request_gop;
 	struct sk_buff *skb;
@@ -1269,24 +1255,39 @@ static unsigned xenvif_tx_build_gops(struct xenvif *vif, int budget)
 			}
 		}
 
-		xenvif_tx_create_gop(vif, pending_idx, &txreq, gop);
-
-		gop++;
-
 		XENVIF_TX_CB(skb)->pending_idx = pending_idx;
 
 		__skb_put(skb, data_len);
+		vif->tx_copy_ops[*copy_ops].source.u.ref = txreq.gref;
+		vif->tx_copy_ops[*copy_ops].source.domid = vif->domid;
+		vif->tx_copy_ops[*copy_ops].source.offset = txreq.offset;
+
+		vif->tx_copy_ops[*copy_ops].dest.u.gmfn =
+			virt_to_mfn(skb->data);
+		vif->tx_copy_ops[*copy_ops].dest.domid = DOMID_SELF;
+		vif->tx_copy_ops[*copy_ops].dest.offset =
+			offset_in_page(skb->data);
+
+		vif->tx_copy_ops[*copy_ops].len = data_len;
+		vif->tx_copy_ops[*copy_ops].flags = GNTCOPY_source_gref;
+
+		(*copy_ops)++;
 
 		skb_shinfo(skb)->nr_frags = ret;
 		if (data_len < txreq.size) {
 			skb_shinfo(skb)->nr_frags++;
 			frag_set_pending_idx(&skb_shinfo(skb)->frags[0],
 					     pending_idx);
+			xenvif_tx_create_gop(vif, pending_idx, &txreq, gop);
+			gop++;
 		} else {
 			frag_set_pending_idx(&skb_shinfo(skb)->frags[0],
 					     INVALID_PENDING_IDX);
+			memcpy(&vif->pending_tx_info[pending_idx].req, &txreq,
+			       sizeof(txreq));
 		}
 
+
 		vif->pending_cons++;
 
 		request_gop = xenvif_get_requests(vif, skb, txfrags, gop);
@@ -1301,11 +1302,13 @@ static unsigned xenvif_tx_build_gops(struct xenvif *vif, int budget)
 
 		vif->tx.req_cons = idx;
 
-		if ((gop-vif->tx_map_ops) >= ARRAY_SIZE(vif->tx_map_ops))
+		if (((gop-vif->tx_map_ops) >= ARRAY_SIZE(vif->tx_map_ops)) ||
+		    (*copy_ops >= ARRAY_SIZE(vif->tx_map_ops)))
 			break;
 	}
 
-	return gop - vif->tx_map_ops;
+	(*map_ops) = gop - vif->tx_map_ops;
+	return;
 }
 
 /* Consolidate skb with a frag_list into a brand new one with local pages on
@@ -1377,6 +1380,7 @@ static int xenvif_handle_frag_list(struct xenvif *vif, struct sk_buff *skb)
 static int xenvif_tx_submit(struct xenvif *vif)
 {
 	struct gnttab_map_grant_ref *gop_map = vif->tx_map_ops;
+	struct gnttab_copy *gop_copy = vif->tx_copy_ops;
 	struct sk_buff *skb;
 	int work_done = 0;
 
@@ -1389,7 +1393,7 @@ static int xenvif_tx_submit(struct xenvif *vif)
 		txp = &vif->pending_tx_info[pending_idx].req;
 
 		/* Check the remap error code. */
-		if (unlikely(xenvif_tx_check_gop(vif, skb, &gop_map))) {
+		if (unlikely(xenvif_tx_check_gop(vif, skb, &gop_map, &gop_copy))) {
 			netdev_dbg(vif->dev, "netback grant failed.\n");
 			skb_shinfo(skb)->nr_frags = 0;
 			kfree_skb(skb);
@@ -1397,19 +1401,15 @@ static int xenvif_tx_submit(struct xenvif *vif)
 		}
 
 		data_len = skb->len;
-		memcpy(skb->data,
-		       (void *)(idx_to_kaddr(vif, pending_idx)|txp->offset),
-		       data_len);
 		callback_param(vif, pending_idx).ctx = NULL;
 		if (data_len < txp->size) {
 			/* Append the packet payload as a fragment. */
 			txp->offset += data_len;
 			txp->size -= data_len;
-			skb_shinfo(skb)->destructor_arg =
-				&callback_param(vif, pending_idx);
 		} else {
 			/* Schedule a response immediately. */
-			xenvif_idx_unmap(vif, pending_idx);
+			xenvif_idx_release(vif, pending_idx,
+					   XEN_NETIF_RSP_OKAY);
 		}
 
 		if (txp->flags & XEN_NETTXF_csum_blank)
@@ -1588,22 +1588,26 @@ static inline void xenvif_tx_dealloc_action(struct xenvif *vif)
 /* Called after netfront has transmitted */
 int xenvif_tx_action(struct xenvif *vif, int budget)
 {
-	unsigned nr_mops;
+	unsigned nr_mops, nr_cops = 0;
 	int work_done, ret;
 
 	if (unlikely(!tx_work_todo(vif)))
 		return 0;
 
-	nr_mops = xenvif_tx_build_gops(vif, budget);
+	xenvif_tx_build_gops(vif, budget, &nr_cops, &nr_mops);
 
-	if (nr_mops == 0)
+	if (nr_cops == 0)
 		return 0;
-
-	ret = gnttab_map_refs(vif->tx_map_ops,
-			      NULL,
-			      vif->pages_to_map,
-			      nr_mops);
-	BUG_ON(ret);
+	else {
+		gnttab_batch_copy(vif->tx_copy_ops, nr_cops);
+		if (nr_mops != 0) {
+			ret = gnttab_map_refs(vif->tx_map_ops,
+					      NULL,
+					      vif->pages_to_map,
+					      nr_mops);
+			BUG_ON(ret);
+		}
+	}
 
 	work_done = xenvif_tx_submit(vif);
 

[PATCH net-next v2 2/2] xen-netback: Grant copy the header instead of map and memcpy

[Zoltan Kiss]

An old inefficiency of the TX path that we are grant mapping the first slot,
and then copy the header part to the linear area. Instead, doing a grant copy
for that header straight on is more reasonable. Especially because there are
ongoing efforts to make Xen avoiding TLB flush after unmap when the page were
not touched in Dom0. In the original way the memcpy ruined that.
The key changes:
- the vif has a tx_copy_ops array again
- xenvif_tx_build_gops sets up the grant copy operations
- we don't have to figure out whether the header and first frag are on the same
  grant mapped page or not
Note, we only grant copy PKT_PROT_LEN bytes from the first slot, the rest (if
any) will be on the first frag, which is grant mapped. If the first slot is
smaller than PKT_PROT_LEN, then we grant copy that, and later __pskb_pull_tail
will pull more from the frags (if any)

Unrelated, but I've made a small refactoring in xenvif_get_extras as well.

Signed-off-by: Zoltan Kiss <zoltan.kiss@citrix.com>
---
v2:
- extend commit message
- add patch to rename map ops

diff --git a/drivers/net/xen-netback/common.h b/drivers/net/xen-netback/common.h
index 89b2d42..c995532 100644
--- a/drivers/net/xen-netback/common.h
+++ b/drivers/net/xen-netback/common.h
@@ -119,6 +119,7 @@ struct xenvif {
 	struct pending_tx_info pending_tx_info[MAX_PENDING_REQS];
 	grant_handle_t grant_tx_handle[MAX_PENDING_REQS];
 
+	struct gnttab_copy tx_copy_ops[MAX_PENDING_REQS];
 	struct gnttab_map_grant_ref tx_map_ops[MAX_PENDING_REQS];
 	struct gnttab_unmap_grant_ref tx_unmap_ops[MAX_PENDING_REQS];
 	/* passed to gnttab_[un]map_refs with pages under (un)mapping */
diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index e781366..ba11ff5 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -915,35 +915,30 @@ static inline void xenvif_grant_handle_reset(struct xenvif *vif,
 
 static int xenvif_tx_check_gop(struct xenvif *vif,
 			       struct sk_buff *skb,
-			       struct gnttab_map_grant_ref **gopp_map)
+			       struct gnttab_map_grant_ref **gopp_map,
+			       struct gnttab_copy **gopp_copy)
 {
 	struct gnttab_map_grant_ref *gop_map = *gopp_map;
 	u16 pending_idx = XENVIF_TX_CB(skb)->pending_idx;
 	struct skb_shared_info *shinfo = skb_shinfo(skb);
-	struct pending_tx_info *tx_info;
 	int nr_frags = shinfo->nr_frags;
-	int i, err, start;
+	int i, err;
 	struct sk_buff *first_skb = NULL;
 
 	/* Check status of header. */
-	err = gop_map->status;
+	err = (*gopp_copy)->status;
+	(*gopp_copy)++;
 	if (unlikely(err))
 		xenvif_idx_release(vif, pending_idx, XEN_NETIF_RSP_ERROR);
-	else
-		xenvif_grant_handle_set(vif, pending_idx , gop_map->handle);
-
-	/* Skip first skb fragment if it is on same page as header fragment. */
-	start = (frag_get_pending_idx(&shinfo->frags[0]) == pending_idx);
 
 check_frags:
-	for (i = start; i < nr_frags; i++) {
+	for (i = 0; i < nr_frags; i++, gop_map++) {
 		int j, newerr;
 
 		pending_idx = frag_get_pending_idx(&shinfo->frags[i]);
-		tx_info = &vif->pending_tx_info[pending_idx];
 
 		/* Check error status: if okay then remember grant handle. */
-		newerr = (++gop_map)->status;
+		newerr = (gop_map)->status;
 
 		if (likely(!newerr)) {
 			xenvif_grant_handle_set(vif,
@@ -961,13 +956,8 @@ check_frags:
 		/* Not the first error? Preceding frags already invalidated. */
 		if (err)
 			continue;
-		/* First error: invalidate header and preceding fragments. */
-		if (!first_skb)
-			pending_idx = XENVIF_TX_CB(skb)->pending_idx;
-		else
-			pending_idx = XENVIF_TX_CB(skb)->pending_idx;
-		xenvif_idx_unmap(vif, pending_idx);
-		for (j = start; j < i; j++) {
+		/* First error: invalidate preceding fragments. */
+		for (j = 0; j < i; j++) {
 			pending_idx = frag_get_pending_idx(&shinfo->frags[j]);
 			xenvif_idx_unmap(vif, pending_idx);
 		}
@@ -981,7 +971,6 @@ check_frags:
 		skb = shinfo->frag_list;
 		shinfo = skb_shinfo(skb);
 		nr_frags = shinfo->nr_frags;
-		start = 0;
 
 		goto check_frags;
 	}
@@ -992,15 +981,13 @@ check_frags:
 	if (first_skb && err) {
 		int j;
 		shinfo = skb_shinfo(first_skb);
-		pending_idx = XENVIF_TX_CB(skb)->pending_idx;
-		start = (frag_get_pending_idx(&shinfo->frags[0]) == pending_idx);
-		for (j = start; j < shinfo->nr_frags; j++) {
+		for (j = 0; j < shinfo->nr_frags; j++) {
 			pending_idx = frag_get_pending_idx(&shinfo->frags[j]);
 			xenvif_idx_unmap(vif, pending_idx);
 		}
 	}
 
-	*gopp_map = gop_map + 1;
+	*gopp_map = gop_map;
 	return err;
 }
 
@@ -1011,9 +998,6 @@ static void xenvif_fill_frags(struct xenvif *vif, struct sk_buff *skb)
 	int i;
 	u16 prev_pending_idx = INVALID_PENDING_IDX;
 
-	if (skb_shinfo(skb)->destructor_arg)
-		prev_pending_idx = XENVIF_TX_CB(skb)->pending_idx;
-
 	for (i = 0; i < nr_frags; i++) {
 		skb_frag_t *frag = shinfo->frags + i;
 		struct xen_netif_tx_request *txp;
@@ -1023,10 +1007,10 @@ static void xenvif_fill_frags(struct xenvif *vif, struct sk_buff *skb)
 		pending_idx = frag_get_pending_idx(frag);
 
 		/* If this is not the first frag, chain it to the previous*/
-		if (unlikely(prev_pending_idx == INVALID_PENDING_IDX))
+		if (prev_pending_idx == INVALID_PENDING_IDX)
 			skb_shinfo(skb)->destructor_arg =
 				&callback_param(vif, pending_idx);
-		else if (likely(pending_idx != prev_pending_idx))
+		else
 			callback_param(vif, prev_pending_idx).ctx =
 				&callback_param(vif, pending_idx);
 
@@ -1067,9 +1051,9 @@ static int xenvif_get_extras(struct xenvif *vif,
 
 		memcpy(&extra, RING_GET_REQUEST(&vif->tx, cons),
 		       sizeof(extra));
+		vif->tx.req_cons = ++cons;
 		if (unlikely(!extra.type ||
 			     extra.type >= XEN_NETIF_EXTRA_TYPE_MAX)) {
-			vif->tx.req_cons = ++cons;
 			netdev_err(vif->dev,
 				   "Invalid extra type: %d\n", extra.type);
 			xenvif_fatal_tx_err(vif);
@@ -1077,7 +1061,6 @@ static int xenvif_get_extras(struct xenvif *vif,
 		}
 
 		memcpy(&extras[extra.type - 1], &extra, sizeof(extra));
-		vif->tx.req_cons = ++cons;
 	} while (extra.flags & XEN_NETIF_EXTRA_FLAG_MORE);
 
 	return work_to_do;
@@ -1166,7 +1149,10 @@ static bool tx_credit_exceeded(struct xenvif *vif, unsigned size)
 	return false;
 }
 
-static unsigned xenvif_tx_build_gops(struct xenvif *vif, int budget)
+static void xenvif_tx_build_gops(struct xenvif *vif,
+				     int budget,
+				     unsigned *copy_ops,
+				     unsigned *map_ops)
 {
 	struct gnttab_map_grant_ref *gop = vif->tx_map_ops, *request_gop;
 	struct sk_buff *skb;
@@ -1269,24 +1255,39 @@ static unsigned xenvif_tx_build_gops(struct xenvif *vif, int budget)
 			}
 		}
 
-		xenvif_tx_create_gop(vif, pending_idx, &txreq, gop);
-
-		gop++;
-
 		XENVIF_TX_CB(skb)->pending_idx = pending_idx;
 
 		__skb_put(skb, data_len);
+		vif->tx_copy_ops[*copy_ops].source.u.ref = txreq.gref;
+		vif->tx_copy_ops[*copy_ops].source.domid = vif->domid;
+		vif->tx_copy_ops[*copy_ops].source.offset = txreq.offset;
+
+		vif->tx_copy_ops[*copy_ops].dest.u.gmfn =
+			virt_to_mfn(skb->data);
+		vif->tx_copy_ops[*copy_ops].dest.domid = DOMID_SELF;
+		vif->tx_copy_ops[*copy_ops].dest.offset =
+			offset_in_page(skb->data);
+
+		vif->tx_copy_ops[*copy_ops].len = data_len;
+		vif->tx_copy_ops[*copy_ops].flags = GNTCOPY_source_gref;
+
+		(*copy_ops)++;
 
 		skb_shinfo(skb)->nr_frags = ret;
 		if (data_len < txreq.size) {
 			skb_shinfo(skb)->nr_frags++;
 			frag_set_pending_idx(&skb_shinfo(skb)->frags[0],
 					     pending_idx);
+			xenvif_tx_create_gop(vif, pending_idx, &txreq, gop);
+			gop++;
 		} else {
 			frag_set_pending_idx(&skb_shinfo(skb)->frags[0],
 					     INVALID_PENDING_IDX);
+			memcpy(&vif->pending_tx_info[pending_idx].req, &txreq,
+			       sizeof(txreq));
 		}
 
+
 		vif->pending_cons++;
 
 		request_gop = xenvif_get_requests(vif, skb, txfrags, gop);
@@ -1301,11 +1302,13 @@ static unsigned xenvif_tx_build_gops(struct xenvif *vif, int budget)
 
 		vif->tx.req_cons = idx;
 
-		if ((gop-vif->tx_map_ops) >= ARRAY_SIZE(vif->tx_map_ops))
+		if (((gop-vif->tx_map_ops) >= ARRAY_SIZE(vif->tx_map_ops)) ||
+		    (*copy_ops >= ARRAY_SIZE(vif->tx_map_ops)))
 			break;
 	}
 
-	return gop - vif->tx_map_ops;
+	(*map_ops) = gop - vif->tx_map_ops;
+	return;
 }
 
 /* Consolidate skb with a frag_list into a brand new one with local pages on
@@ -1377,6 +1380,7 @@ static int xenvif_handle_frag_list(struct xenvif *vif, struct sk_buff *skb)
 static int xenvif_tx_submit(struct xenvif *vif)
 {
 	struct gnttab_map_grant_ref *gop_map = vif->tx_map_ops;
+	struct gnttab_copy *gop_copy = vif->tx_copy_ops;
 	struct sk_buff *skb;
 	int work_done = 0;
 
@@ -1389,7 +1393,7 @@ static int xenvif_tx_submit(struct xenvif *vif)
 		txp = &vif->pending_tx_info[pending_idx].req;
 
 		/* Check the remap error code. */
-		if (unlikely(xenvif_tx_check_gop(vif, skb, &gop_map))) {
+		if (unlikely(xenvif_tx_check_gop(vif, skb, &gop_map, &gop_copy))) {
 			netdev_dbg(vif->dev, "netback grant failed.\n");
 			skb_shinfo(skb)->nr_frags = 0;
 			kfree_skb(skb);
@@ -1397,19 +1401,15 @@ static int xenvif_tx_submit(struct xenvif *vif)
 		}
 
 		data_len = skb->len;
-		memcpy(skb->data,
-		       (void *)(idx_to_kaddr(vif, pending_idx)|txp->offset),
-		       data_len);
 		callback_param(vif, pending_idx).ctx = NULL;
 		if (data_len < txp->size) {
 			/* Append the packet payload as a fragment. */
 			txp->offset += data_len;
 			txp->size -= data_len;
-			skb_shinfo(skb)->destructor_arg =
-				&callback_param(vif, pending_idx);
 		} else {
 			/* Schedule a response immediately. */
-			xenvif_idx_unmap(vif, pending_idx);
+			xenvif_idx_release(vif, pending_idx,
+					   XEN_NETIF_RSP_OKAY);
 		}
 
 		if (txp->flags & XEN_NETTXF_csum_blank)
@@ -1588,22 +1588,26 @@ static inline void xenvif_tx_dealloc_action(struct xenvif *vif)
 /* Called after netfront has transmitted */
 int xenvif_tx_action(struct xenvif *vif, int budget)
 {
-	unsigned nr_mops;
+	unsigned nr_mops, nr_cops = 0;
 	int work_done, ret;
 
 	if (unlikely(!tx_work_todo(vif)))
 		return 0;
 
-	nr_mops = xenvif_tx_build_gops(vif, budget);
+	xenvif_tx_build_gops(vif, budget, &nr_cops, &nr_mops);
 
-	if (nr_mops == 0)
+	if (nr_cops == 0)
 		return 0;
-
-	ret = gnttab_map_refs(vif->tx_map_ops,
-			      NULL,
-			      vif->pages_to_map,
-			      nr_mops);
-	BUG_ON(ret);
+	else {
+		gnttab_batch_copy(vif->tx_copy_ops, nr_cops);
+		if (nr_mops != 0) {
+			ret = gnttab_map_refs(vif->tx_map_ops,
+					      NULL,
+					      vif->pages_to_map,
+					      nr_mops);
+			BUG_ON(ret);
+		}
+	}
 
 	work_done = xenvif_tx_submit(vif);

RE: [PATCH net-next v2 2/2] xen-netback: Grant copy the header instead of map and memcpy

[Paul Durrant]

> -----Original Message-----
> From: Zoltan Kiss
> Sent: 31 March 2014 16:09
> To: Ian Campbell; Wei Liu; xen-devel@lists.xenproject.org
> Cc: Paul Durrant; netdev@vger.kernel.org; linux-kernel@vger.kernel.org;
> Jonathan Davies; Zoltan Kiss
> Subject: [PATCH net-next v2 2/2] xen-netback: Grant copy the header
> instead of map and memcpy
> 
> An old inefficiency of the TX path that we are grant mapping the first slot,
> and then copy the header part to the linear area. Instead, doing a grant copy
> for that header straight on is more reasonable. Especially because there are
> ongoing efforts to make Xen avoiding TLB flush after unmap when the page
> were
> not touched in Dom0. In the original way the memcpy ruined that.
> The key changes:
> - the vif has a tx_copy_ops array again
> - xenvif_tx_build_gops sets up the grant copy operations
> - we don't have to figure out whether the header and first frag are on the
> same
>   grant mapped page or not
> Note, we only grant copy PKT_PROT_LEN bytes from the first slot, the rest (if
> any) will be on the first frag, which is grant mapped. If the first slot is
> smaller than PKT_PROT_LEN, then we grant copy that, and later
> __pskb_pull_tail
> will pull more from the frags (if any)
> 
> Unrelated, but I've made a small refactoring in xenvif_get_extras as well.
> 
> Signed-off-by: Zoltan Kiss <zoltan.kiss@citrix.com>
> ---
> v2:
> - extend commit message
> - add patch to rename map ops
> 
> diff --git a/drivers/net/xen-netback/common.h b/drivers/net/xen-
> netback/common.h
> index 89b2d42..c995532 100644
> --- a/drivers/net/xen-netback/common.h
> +++ b/drivers/net/xen-netback/common.h
> @@ -119,6 +119,7 @@ struct xenvif {
>  	struct pending_tx_info pending_tx_info[MAX_PENDING_REQS];
>  	grant_handle_t grant_tx_handle[MAX_PENDING_REQS];
> 
> +	struct gnttab_copy tx_copy_ops[MAX_PENDING_REQS];
>  	struct gnttab_map_grant_ref tx_map_ops[MAX_PENDING_REQS];
>  	struct gnttab_unmap_grant_ref
> tx_unmap_ops[MAX_PENDING_REQS];
>  	/* passed to gnttab_[un]map_refs with pages under (un)mapping */
> diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-
> netback/netback.c
> index e781366..ba11ff5 100644
> --- a/drivers/net/xen-netback/netback.c
> +++ b/drivers/net/xen-netback/netback.c
> @@ -915,35 +915,30 @@ static inline void xenvif_grant_handle_reset(struct
> xenvif *vif,
> 
>  static int xenvif_tx_check_gop(struct xenvif *vif,
>  			       struct sk_buff *skb,
> -			       struct gnttab_map_grant_ref **gopp_map)
> +			       struct gnttab_map_grant_ref **gopp_map,
> +			       struct gnttab_copy **gopp_copy)
>  {
>  	struct gnttab_map_grant_ref *gop_map = *gopp_map;
>  	u16 pending_idx = XENVIF_TX_CB(skb)->pending_idx;
>  	struct skb_shared_info *shinfo = skb_shinfo(skb);
> -	struct pending_tx_info *tx_info;
>  	int nr_frags = shinfo->nr_frags;
> -	int i, err, start;
> +	int i, err;
>  	struct sk_buff *first_skb = NULL;
> 
>  	/* Check status of header. */
> -	err = gop_map->status;
> +	err = (*gopp_copy)->status;
> +	(*gopp_copy)++;

I guess there's no undo work in the case of a copy op so you can bump the copy count here, but it might have been nicer to pair it with the update to the map count.

>  	if (unlikely(err))
>  		xenvif_idx_release(vif, pending_idx,
> XEN_NETIF_RSP_ERROR);
> -	else
> -		xenvif_grant_handle_set(vif, pending_idx , gop_map-
> >handle);
> -
> -	/* Skip first skb fragment if it is on same page as header fragment. */
> -	start = (frag_get_pending_idx(&shinfo->frags[0]) == pending_idx);
> 
>  check_frags:
> -	for (i = start; i < nr_frags; i++) {
> +	for (i = 0; i < nr_frags; i++, gop_map++) {
>  		int j, newerr;
> 
>  		pending_idx = frag_get_pending_idx(&shinfo->frags[i]);
> -		tx_info = &vif->pending_tx_info[pending_idx];
> 
>  		/* Check error status: if okay then remember grant handle.
> */
> -		newerr = (++gop_map)->status;
> +		newerr = (gop_map)->status;
> 
>  		if (likely(!newerr)) {
>  			xenvif_grant_handle_set(vif,
> @@ -961,13 +956,8 @@ check_frags:
>  		/* Not the first error? Preceding frags already invalidated. */
>  		if (err)
>  			continue;
> -		/* First error: invalidate header and preceding fragments. */
> -		if (!first_skb)
> -			pending_idx = XENVIF_TX_CB(skb)->pending_idx;
> -		else
> -			pending_idx = XENVIF_TX_CB(skb)->pending_idx;
> -		xenvif_idx_unmap(vif, pending_idx);
> -		for (j = start; j < i; j++) {
> +		/* First error: invalidate preceding fragments. */
> +		for (j = 0; j < i; j++) {
>  			pending_idx = frag_get_pending_idx(&shinfo-
> >frags[j]);
>  			xenvif_idx_unmap(vif, pending_idx);
>  		}
> @@ -981,7 +971,6 @@ check_frags:
>  		skb = shinfo->frag_list;
>  		shinfo = skb_shinfo(skb);
>  		nr_frags = shinfo->nr_frags;
> -		start = 0;
> 
>  		goto check_frags;
>  	}
> @@ -992,15 +981,13 @@ check_frags:
>  	if (first_skb && err) {
>  		int j;
>  		shinfo = skb_shinfo(first_skb);
> -		pending_idx = XENVIF_TX_CB(skb)->pending_idx;
> -		start = (frag_get_pending_idx(&shinfo->frags[0]) ==
> pending_idx);
> -		for (j = start; j < shinfo->nr_frags; j++) {
> +		for (j = 0; j < shinfo->nr_frags; j++) {
>  			pending_idx = frag_get_pending_idx(&shinfo-
> >frags[j]);
>  			xenvif_idx_unmap(vif, pending_idx);
>  		}
>  	}
> 
> -	*gopp_map = gop_map + 1;
> +	*gopp_map = gop_map;
>  	return err;
>  }
> 
> @@ -1011,9 +998,6 @@ static void xenvif_fill_frags(struct xenvif *vif, struct
> sk_buff *skb)
>  	int i;
>  	u16 prev_pending_idx = INVALID_PENDING_IDX;
> 
> -	if (skb_shinfo(skb)->destructor_arg)
> -		prev_pending_idx = XENVIF_TX_CB(skb)->pending_idx;
> -
>  	for (i = 0; i < nr_frags; i++) {
>  		skb_frag_t *frag = shinfo->frags + i;
>  		struct xen_netif_tx_request *txp;
> @@ -1023,10 +1007,10 @@ static void xenvif_fill_frags(struct xenvif *vif,
> struct sk_buff *skb)
>  		pending_idx = frag_get_pending_idx(frag);
> 
>  		/* If this is not the first frag, chain it to the previous*/
> -		if (unlikely(prev_pending_idx == INVALID_PENDING_IDX))
> +		if (prev_pending_idx == INVALID_PENDING_IDX)
>  			skb_shinfo(skb)->destructor_arg =
>  				&callback_param(vif, pending_idx);
> -		else if (likely(pending_idx != prev_pending_idx))
> +		else
>  			callback_param(vif, prev_pending_idx).ctx =
>  				&callback_param(vif, pending_idx);
> 
> @@ -1067,9 +1051,9 @@ static int xenvif_get_extras(struct xenvif *vif,
> 
>  		memcpy(&extra, RING_GET_REQUEST(&vif->tx, cons),
>  		       sizeof(extra));
> +		vif->tx.req_cons = ++cons;
>  		if (unlikely(!extra.type ||
>  			     extra.type >= XEN_NETIF_EXTRA_TYPE_MAX)) {
> -			vif->tx.req_cons = ++cons;
>  			netdev_err(vif->dev,
>  				   "Invalid extra type: %d\n", extra.type);
>  			xenvif_fatal_tx_err(vif);
> @@ -1077,7 +1061,6 @@ static int xenvif_get_extras(struct xenvif *vif,
>  		}
> 
>  		memcpy(&extras[extra.type - 1], &extra, sizeof(extra));
> -		vif->tx.req_cons = ++cons;

I know you called this out as unrelated, but I still think it would be better in a separate patch.

>  	} while (extra.flags & XEN_NETIF_EXTRA_FLAG_MORE);
> 
>  	return work_to_do;
> @@ -1166,7 +1149,10 @@ static bool tx_credit_exceeded(struct xenvif *vif,
> unsigned size)
>  	return false;
>  }
> 
> -static unsigned xenvif_tx_build_gops(struct xenvif *vif, int budget)
> +static void xenvif_tx_build_gops(struct xenvif *vif,
> +				     int budget,
> +				     unsigned *copy_ops,
> +				     unsigned *map_ops)
>  {
>  	struct gnttab_map_grant_ref *gop = vif->tx_map_ops,
> *request_gop;
>  	struct sk_buff *skb;
> @@ -1269,24 +1255,39 @@ static unsigned xenvif_tx_build_gops(struct
> xenvif *vif, int budget)
>  			}
>  		}
> 
> -		xenvif_tx_create_gop(vif, pending_idx, &txreq, gop);
> -
> -		gop++;
> -
>  		XENVIF_TX_CB(skb)->pending_idx = pending_idx;
> 
>  		__skb_put(skb, data_len);
> +		vif->tx_copy_ops[*copy_ops].source.u.ref = txreq.gref;
> +		vif->tx_copy_ops[*copy_ops].source.domid = vif->domid;
> +		vif->tx_copy_ops[*copy_ops].source.offset = txreq.offset;
> +
> +		vif->tx_copy_ops[*copy_ops].dest.u.gmfn =
> +			virt_to_mfn(skb->data);
> +		vif->tx_copy_ops[*copy_ops].dest.domid = DOMID_SELF;
> +		vif->tx_copy_ops[*copy_ops].dest.offset =
> +			offset_in_page(skb->data);
> +
> +		vif->tx_copy_ops[*copy_ops].len = data_len;
> +		vif->tx_copy_ops[*copy_ops].flags =
> GNTCOPY_source_gref;
> +
> +		(*copy_ops)++;
> 
>  		skb_shinfo(skb)->nr_frags = ret;
>  		if (data_len < txreq.size) {
>  			skb_shinfo(skb)->nr_frags++;
>  			frag_set_pending_idx(&skb_shinfo(skb)->frags[0],
>  					     pending_idx);
> +			xenvif_tx_create_gop(vif, pending_idx, &txreq,
> gop);
> +			gop++;
>  		} else {
>  			frag_set_pending_idx(&skb_shinfo(skb)->frags[0],
>  					     INVALID_PENDING_IDX);
> +			memcpy(&vif->pending_tx_info[pending_idx].req,
> &txreq,
> +			       sizeof(txreq));
>  		}
> 
> +

Unnecessary whitespace change.

>  		vif->pending_cons++;
> 
>  		request_gop = xenvif_get_requests(vif, skb, txfrags, gop);
> @@ -1301,11 +1302,13 @@ static unsigned xenvif_tx_build_gops(struct
> xenvif *vif, int budget)
> 
>  		vif->tx.req_cons = idx;
> 
> -		if ((gop-vif->tx_map_ops) >= ARRAY_SIZE(vif-
> >tx_map_ops))
> +		if (((gop-vif->tx_map_ops) >= ARRAY_SIZE(vif-
> >tx_map_ops)) ||
> +		    (*copy_ops >= ARRAY_SIZE(vif->tx_map_ops)))

Do you mean ARRAY_SIZE(vif->tx_copy_ops) here?

>  			break;
>  	}
> 
> -	return gop - vif->tx_map_ops;
> +	(*map_ops) = gop - vif->tx_map_ops;
> +	return;
>  }
> 
>  /* Consolidate skb with a frag_list into a brand new one with local pages on
> @@ -1377,6 +1380,7 @@ static int xenvif_handle_frag_list(struct xenvif *vif,
> struct sk_buff *skb)
>  static int xenvif_tx_submit(struct xenvif *vif)
>  {
>  	struct gnttab_map_grant_ref *gop_map = vif->tx_map_ops;
> +	struct gnttab_copy *gop_copy = vif->tx_copy_ops;
>  	struct sk_buff *skb;
>  	int work_done = 0;
> 
> @@ -1389,7 +1393,7 @@ static int xenvif_tx_submit(struct xenvif *vif)
>  		txp = &vif->pending_tx_info[pending_idx].req;
> 
>  		/* Check the remap error code. */
> -		if (unlikely(xenvif_tx_check_gop(vif, skb, &gop_map))) {
> +		if (unlikely(xenvif_tx_check_gop(vif, skb, &gop_map,
> &gop_copy))) {
>  			netdev_dbg(vif->dev, "netback grant failed.\n");

It could have been the copy that failed. You should probably change the error message.

>  			skb_shinfo(skb)->nr_frags = 0;
>  			kfree_skb(skb);
> @@ -1397,19 +1401,15 @@ static int xenvif_tx_submit(struct xenvif *vif)
>  		}
> 
>  		data_len = skb->len;
> -		memcpy(skb->data,
> -		       (void *)(idx_to_kaddr(vif, pending_idx)|txp->offset),
> -		       data_len);
>  		callback_param(vif, pending_idx).ctx = NULL;
>  		if (data_len < txp->size) {
>  			/* Append the packet payload as a fragment. */
>  			txp->offset += data_len;
>  			txp->size -= data_len;
> -			skb_shinfo(skb)->destructor_arg =
> -				&callback_param(vif, pending_idx);
>  		} else {
>  			/* Schedule a response immediately. */
> -			xenvif_idx_unmap(vif, pending_idx);
> +			xenvif_idx_release(vif, pending_idx,
> +					   XEN_NETIF_RSP_OKAY);
>  		}
> 
>  		if (txp->flags & XEN_NETTXF_csum_blank)
> @@ -1588,22 +1588,26 @@ static inline void xenvif_tx_dealloc_action(struct
> xenvif *vif)
>  /* Called after netfront has transmitted */
>  int xenvif_tx_action(struct xenvif *vif, int budget)
>  {
> -	unsigned nr_mops;
> +	unsigned nr_mops, nr_cops = 0;
>  	int work_done, ret;
> 
>  	if (unlikely(!tx_work_todo(vif)))
>  		return 0;
> 
> -	nr_mops = xenvif_tx_build_gops(vif, budget);
> +	xenvif_tx_build_gops(vif, budget, &nr_cops, &nr_mops);
> 
> -	if (nr_mops == 0)
> +	if (nr_cops == 0)
>  		return 0;
> -
> -	ret = gnttab_map_refs(vif->tx_map_ops,
> -			      NULL,
> -			      vif->pages_to_map,
> -			      nr_mops);
> -	BUG_ON(ret);
> +	else {

Do you need an 'else' here? Unless I'm misreading the diff your previous clause returns.

  Paul

> +		gnttab_batch_copy(vif->tx_copy_ops, nr_cops);
> +		if (nr_mops != 0) {
> +			ret = gnttab_map_refs(vif->tx_map_ops,
> +					      NULL,
> +					      vif->pages_to_map,
> +					      nr_mops);
> +			BUG_ON(ret);
> +		}
> +	}
> 
>  	work_done = xenvif_tx_submit(vif);
> 

Re: [PATCH net-next v2 2/2] xen-netback: Grant copy the header instead of map and memcpy

[Paul Durrant]

> -----Original Message-----
> From: Zoltan Kiss
> Sent: 31 March 2014 16:09
> To: Ian Campbell; Wei Liu; xen-devel@lists.xenproject.org
> Cc: Paul Durrant; netdev@vger.kernel.org; linux-kernel@vger.kernel.org;
> Jonathan Davies; Zoltan Kiss
> Subject: [PATCH net-next v2 2/2] xen-netback: Grant copy the header
> instead of map and memcpy
> 
> An old inefficiency of the TX path that we are grant mapping the first slot,
> and then copy the header part to the linear area. Instead, doing a grant copy
> for that header straight on is more reasonable. Especially because there are
> ongoing efforts to make Xen avoiding TLB flush after unmap when the page
> were
> not touched in Dom0. In the original way the memcpy ruined that.
> The key changes:
> - the vif has a tx_copy_ops array again
> - xenvif_tx_build_gops sets up the grant copy operations
> - we don't have to figure out whether the header and first frag are on the
> same
>   grant mapped page or not
> Note, we only grant copy PKT_PROT_LEN bytes from the first slot, the rest (if
> any) will be on the first frag, which is grant mapped. If the first slot is
> smaller than PKT_PROT_LEN, then we grant copy that, and later
> __pskb_pull_tail
> will pull more from the frags (if any)
> 
> Unrelated, but I've made a small refactoring in xenvif_get_extras as well.
> 
> Signed-off-by: Zoltan Kiss <zoltan.kiss@citrix.com>
> ---
> v2:
> - extend commit message
> - add patch to rename map ops
> 
> diff --git a/drivers/net/xen-netback/common.h b/drivers/net/xen-
> netback/common.h
> index 89b2d42..c995532 100644
> --- a/drivers/net/xen-netback/common.h
> +++ b/drivers/net/xen-netback/common.h
> @@ -119,6 +119,7 @@ struct xenvif {
>  	struct pending_tx_info pending_tx_info[MAX_PENDING_REQS];
>  	grant_handle_t grant_tx_handle[MAX_PENDING_REQS];
> 
> +	struct gnttab_copy tx_copy_ops[MAX_PENDING_REQS];
>  	struct gnttab_map_grant_ref tx_map_ops[MAX_PENDING_REQS];
>  	struct gnttab_unmap_grant_ref
> tx_unmap_ops[MAX_PENDING_REQS];
>  	/* passed to gnttab_[un]map_refs with pages under (un)mapping */
> diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-
> netback/netback.c
> index e781366..ba11ff5 100644
> --- a/drivers/net/xen-netback/netback.c
> +++ b/drivers/net/xen-netback/netback.c
> @@ -915,35 +915,30 @@ static inline void xenvif_grant_handle_reset(struct
> xenvif *vif,
> 
>  static int xenvif_tx_check_gop(struct xenvif *vif,
>  			       struct sk_buff *skb,
> -			       struct gnttab_map_grant_ref **gopp_map)
> +			       struct gnttab_map_grant_ref **gopp_map,
> +			       struct gnttab_copy **gopp_copy)
>  {
>  	struct gnttab_map_grant_ref *gop_map = *gopp_map;
>  	u16 pending_idx = XENVIF_TX_CB(skb)->pending_idx;
>  	struct skb_shared_info *shinfo = skb_shinfo(skb);
> -	struct pending_tx_info *tx_info;
>  	int nr_frags = shinfo->nr_frags;
> -	int i, err, start;
> +	int i, err;
>  	struct sk_buff *first_skb = NULL;
> 
>  	/* Check status of header. */
> -	err = gop_map->status;
> +	err = (*gopp_copy)->status;
> +	(*gopp_copy)++;

I guess there's no undo work in the case of a copy op so you can bump the copy count here, but it might have been nicer to pair it with the update to the map count.

>  	if (unlikely(err))
>  		xenvif_idx_release(vif, pending_idx,
> XEN_NETIF_RSP_ERROR);
> -	else
> -		xenvif_grant_handle_set(vif, pending_idx , gop_map-
> >handle);
> -
> -	/* Skip first skb fragment if it is on same page as header fragment. */
> -	start = (frag_get_pending_idx(&shinfo->frags[0]) == pending_idx);
> 
>  check_frags:
> -	for (i = start; i < nr_frags; i++) {
> +	for (i = 0; i < nr_frags; i++, gop_map++) {
>  		int j, newerr;
> 
>  		pending_idx = frag_get_pending_idx(&shinfo->frags[i]);
> -		tx_info = &vif->pending_tx_info[pending_idx];
> 
>  		/* Check error status: if okay then remember grant handle.
> */
> -		newerr = (++gop_map)->status;
> +		newerr = (gop_map)->status;
> 
>  		if (likely(!newerr)) {
>  			xenvif_grant_handle_set(vif,
> @@ -961,13 +956,8 @@ check_frags:
>  		/* Not the first error? Preceding frags already invalidated. */
>  		if (err)
>  			continue;
> -		/* First error: invalidate header and preceding fragments. */
> -		if (!first_skb)
> -			pending_idx = XENVIF_TX_CB(skb)->pending_idx;
> -		else
> -			pending_idx = XENVIF_TX_CB(skb)->pending_idx;
> -		xenvif_idx_unmap(vif, pending_idx);
> -		for (j = start; j < i; j++) {
> +		/* First error: invalidate preceding fragments. */
> +		for (j = 0; j < i; j++) {
>  			pending_idx = frag_get_pending_idx(&shinfo-
> >frags[j]);
>  			xenvif_idx_unmap(vif, pending_idx);
>  		}
> @@ -981,7 +971,6 @@ check_frags:
>  		skb = shinfo->frag_list;
>  		shinfo = skb_shinfo(skb);
>  		nr_frags = shinfo->nr_frags;
> -		start = 0;
> 
>  		goto check_frags;
>  	}
> @@ -992,15 +981,13 @@ check_frags:
>  	if (first_skb && err) {
>  		int j;
>  		shinfo = skb_shinfo(first_skb);
> -		pending_idx = XENVIF_TX_CB(skb)->pending_idx;
> -		start = (frag_get_pending_idx(&shinfo->frags[0]) ==
> pending_idx);
> -		for (j = start; j < shinfo->nr_frags; j++) {
> +		for (j = 0; j < shinfo->nr_frags; j++) {
>  			pending_idx = frag_get_pending_idx(&shinfo-
> >frags[j]);
>  			xenvif_idx_unmap(vif, pending_idx);
>  		}
>  	}
> 
> -	*gopp_map = gop_map + 1;
> +	*gopp_map = gop_map;
>  	return err;
>  }
> 
> @@ -1011,9 +998,6 @@ static void xenvif_fill_frags(struct xenvif *vif, struct
> sk_buff *skb)
>  	int i;
>  	u16 prev_pending_idx = INVALID_PENDING_IDX;
> 
> -	if (skb_shinfo(skb)->destructor_arg)
> -		prev_pending_idx = XENVIF_TX_CB(skb)->pending_idx;
> -
>  	for (i = 0; i < nr_frags; i++) {
>  		skb_frag_t *frag = shinfo->frags + i;
>  		struct xen_netif_tx_request *txp;
> @@ -1023,10 +1007,10 @@ static void xenvif_fill_frags(struct xenvif *vif,
> struct sk_buff *skb)
>  		pending_idx = frag_get_pending_idx(frag);
> 
>  		/* If this is not the first frag, chain it to the previous*/
> -		if (unlikely(prev_pending_idx == INVALID_PENDING_IDX))
> +		if (prev_pending_idx == INVALID_PENDING_IDX)
>  			skb_shinfo(skb)->destructor_arg =
>  				&callback_param(vif, pending_idx);
> -		else if (likely(pending_idx != prev_pending_idx))
> +		else
>  			callback_param(vif, prev_pending_idx).ctx =
>  				&callback_param(vif, pending_idx);
> 
> @@ -1067,9 +1051,9 @@ static int xenvif_get_extras(struct xenvif *vif,
> 
>  		memcpy(&extra, RING_GET_REQUEST(&vif->tx, cons),
>  		       sizeof(extra));
> +		vif->tx.req_cons = ++cons;
>  		if (unlikely(!extra.type ||
>  			     extra.type >= XEN_NETIF_EXTRA_TYPE_MAX)) {
> -			vif->tx.req_cons = ++cons;
>  			netdev_err(vif->dev,
>  				   "Invalid extra type: %d\n", extra.type);
>  			xenvif_fatal_tx_err(vif);
> @@ -1077,7 +1061,6 @@ static int xenvif_get_extras(struct xenvif *vif,
>  		}
> 
>  		memcpy(&extras[extra.type - 1], &extra, sizeof(extra));
> -		vif->tx.req_cons = ++cons;

I know you called this out as unrelated, but I still think it would be better in a separate patch.

>  	} while (extra.flags & XEN_NETIF_EXTRA_FLAG_MORE);
> 
>  	return work_to_do;
> @@ -1166,7 +1149,10 @@ static bool tx_credit_exceeded(struct xenvif *vif,
> unsigned size)
>  	return false;
>  }
> 
> -static unsigned xenvif_tx_build_gops(struct xenvif *vif, int budget)
> +static void xenvif_tx_build_gops(struct xenvif *vif,
> +				     int budget,
> +				     unsigned *copy_ops,
> +				     unsigned *map_ops)
>  {
>  	struct gnttab_map_grant_ref *gop = vif->tx_map_ops,
> *request_gop;
>  	struct sk_buff *skb;
> @@ -1269,24 +1255,39 @@ static unsigned xenvif_tx_build_gops(struct
> xenvif *vif, int budget)
>  			}
>  		}
> 
> -		xenvif_tx_create_gop(vif, pending_idx, &txreq, gop);
> -
> -		gop++;
> -
>  		XENVIF_TX_CB(skb)->pending_idx = pending_idx;
> 
>  		__skb_put(skb, data_len);
> +		vif->tx_copy_ops[*copy_ops].source.u.ref = txreq.gref;
> +		vif->tx_copy_ops[*copy_ops].source.domid = vif->domid;
> +		vif->tx_copy_ops[*copy_ops].source.offset = txreq.offset;
> +
> +		vif->tx_copy_ops[*copy_ops].dest.u.gmfn =
> +			virt_to_mfn(skb->data);
> +		vif->tx_copy_ops[*copy_ops].dest.domid = DOMID_SELF;
> +		vif->tx_copy_ops[*copy_ops].dest.offset =
> +			offset_in_page(skb->data);
> +
> +		vif->tx_copy_ops[*copy_ops].len = data_len;
> +		vif->tx_copy_ops[*copy_ops].flags =
> GNTCOPY_source_gref;
> +
> +		(*copy_ops)++;
> 
>  		skb_shinfo(skb)->nr_frags = ret;
>  		if (data_len < txreq.size) {
>  			skb_shinfo(skb)->nr_frags++;
>  			frag_set_pending_idx(&skb_shinfo(skb)->frags[0],
>  					     pending_idx);
> +			xenvif_tx_create_gop(vif, pending_idx, &txreq,
> gop);
> +			gop++;
>  		} else {
>  			frag_set_pending_idx(&skb_shinfo(skb)->frags[0],
>  					     INVALID_PENDING_IDX);
> +			memcpy(&vif->pending_tx_info[pending_idx].req,
> &txreq,
> +			       sizeof(txreq));
>  		}
> 
> +

Unnecessary whitespace change.

>  		vif->pending_cons++;
> 
>  		request_gop = xenvif_get_requests(vif, skb, txfrags, gop);
> @@ -1301,11 +1302,13 @@ static unsigned xenvif_tx_build_gops(struct
> xenvif *vif, int budget)
> 
>  		vif->tx.req_cons = idx;
> 
> -		if ((gop-vif->tx_map_ops) >= ARRAY_SIZE(vif-
> >tx_map_ops))
> +		if (((gop-vif->tx_map_ops) >= ARRAY_SIZE(vif-
> >tx_map_ops)) ||
> +		    (*copy_ops >= ARRAY_SIZE(vif->tx_map_ops)))

Do you mean ARRAY_SIZE(vif->tx_copy_ops) here?

>  			break;
>  	}
> 
> -	return gop - vif->tx_map_ops;
> +	(*map_ops) = gop - vif->tx_map_ops;
> +	return;
>  }
> 
>  /* Consolidate skb with a frag_list into a brand new one with local pages on
> @@ -1377,6 +1380,7 @@ static int xenvif_handle_frag_list(struct xenvif *vif,
> struct sk_buff *skb)
>  static int xenvif_tx_submit(struct xenvif *vif)
>  {
>  	struct gnttab_map_grant_ref *gop_map = vif->tx_map_ops;
> +	struct gnttab_copy *gop_copy = vif->tx_copy_ops;
>  	struct sk_buff *skb;
>  	int work_done = 0;
> 
> @@ -1389,7 +1393,7 @@ static int xenvif_tx_submit(struct xenvif *vif)
>  		txp = &vif->pending_tx_info[pending_idx].req;
> 
>  		/* Check the remap error code. */
> -		if (unlikely(xenvif_tx_check_gop(vif, skb, &gop_map))) {
> +		if (unlikely(xenvif_tx_check_gop(vif, skb, &gop_map,
> &gop_copy))) {
>  			netdev_dbg(vif->dev, "netback grant failed.\n");

It could have been the copy that failed. You should probably change the error message.

>  			skb_shinfo(skb)->nr_frags = 0;
>  			kfree_skb(skb);
> @@ -1397,19 +1401,15 @@ static int xenvif_tx_submit(struct xenvif *vif)
>  		}
> 
>  		data_len = skb->len;
> -		memcpy(skb->data,
> -		       (void *)(idx_to_kaddr(vif, pending_idx)|txp->offset),
> -		       data_len);
>  		callback_param(vif, pending_idx).ctx = NULL;
>  		if (data_len < txp->size) {
>  			/* Append the packet payload as a fragment. */
>  			txp->offset += data_len;
>  			txp->size -= data_len;
> -			skb_shinfo(skb)->destructor_arg =
> -				&callback_param(vif, pending_idx);
>  		} else {
>  			/* Schedule a response immediately. */
> -			xenvif_idx_unmap(vif, pending_idx);
> +			xenvif_idx_release(vif, pending_idx,
> +					   XEN_NETIF_RSP_OKAY);
>  		}
> 
>  		if (txp->flags & XEN_NETTXF_csum_blank)
> @@ -1588,22 +1588,26 @@ static inline void xenvif_tx_dealloc_action(struct
> xenvif *vif)
>  /* Called after netfront has transmitted */
>  int xenvif_tx_action(struct xenvif *vif, int budget)
>  {
> -	unsigned nr_mops;
> +	unsigned nr_mops, nr_cops = 0;
>  	int work_done, ret;
> 
>  	if (unlikely(!tx_work_todo(vif)))
>  		return 0;
> 
> -	nr_mops = xenvif_tx_build_gops(vif, budget);
> +	xenvif_tx_build_gops(vif, budget, &nr_cops, &nr_mops);
> 
> -	if (nr_mops == 0)
> +	if (nr_cops == 0)
>  		return 0;
> -
> -	ret = gnttab_map_refs(vif->tx_map_ops,
> -			      NULL,
> -			      vif->pages_to_map,
> -			      nr_mops);
> -	BUG_ON(ret);
> +	else {

Do you need an 'else' here? Unless I'm misreading the diff your previous clause returns.

  Paul

> +		gnttab_batch_copy(vif->tx_copy_ops, nr_cops);
> +		if (nr_mops != 0) {
> +			ret = gnttab_map_refs(vif->tx_map_ops,
> +					      NULL,
> +					      vif->pages_to_map,
> +					      nr_mops);
> +			BUG_ON(ret);
> +		}
> +	}
> 
>  	work_done = xenvif_tx_submit(vif);
> 

Re: [PATCH net-next v2 1/2] xen-netback: Rename map ops

[Ian Campbell]

On Mon, 2014-03-31 at 16:08 +0100, Zoltan Kiss wrote:
> Rename identifiers to state explicitly that they refer to map ops.
> 
> Signed-off-by: Zoltan Kiss <zoltan.kiss@citrix.com>

On the understanding that this is a pure rename:
Acked-by: Ian Campbell <ian.campbell@citrix.com>

Re: [PATCH net-next v2 1/2] xen-netback: Rename map ops

[Ian Campbell]

On Mon, 2014-03-31 at 16:08 +0100, Zoltan Kiss wrote:
> Rename identifiers to state explicitly that they refer to map ops.
> 
> Signed-off-by: Zoltan Kiss <zoltan.kiss@citrix.com>

On the understanding that this is a pure rename:
Acked-by: Ian Campbell <ian.campbell@citrix.com>

Re: [PATCH net-next v2 2/2] xen-netback: Grant copy the header instead of map and memcpy

[Ian Campbell]

On Mon, 2014-03-31 at 16:08 +0100, Zoltan Kiss wrote:
>  
>  check_frags:
> -	for (i = start; i < nr_frags; i++) {
> +	for (i = 0; i < nr_frags; i++, gop_map++) {
>  		int j, newerr;
>  
>  		pending_idx = frag_get_pending_idx(&shinfo->frags[i]);
> -		tx_info = &vif->pending_tx_info[pending_idx];
>  
>  		/* Check error status: if okay then remember grant handle. */
> -		newerr = (++gop_map)->status;
> +		newerr = (gop_map)->status;

You've reworked the handling of gop_map and when and where it is
incremented, which might be a legit cleanup but does it relate to the
bulk of this change somehow that I'm missing?

>  [...] 
>  		__skb_put(skb, data_len);
> +		vif->tx_copy_ops[*copy_ops].source.u.ref = txreq.gref;
> +		vif->tx_copy_ops[*copy_ops].source.domid = vif->domid;
> +		vif->tx_copy_ops[*copy_ops].source.offset = txreq.offset;
> +
> +		vif->tx_copy_ops[*copy_ops].dest.u.gmfn =
> +			virt_to_mfn(skb->data);
> +		vif->tx_copy_ops[*copy_ops].dest.domid = DOMID_SELF;
> +		vif->tx_copy_ops[*copy_ops].dest.offset =
> +			offset_in_page(skb->data);
> +
> +		vif->tx_copy_ops[*copy_ops].len = data_len;
> +		vif->tx_copy_ops[*copy_ops].flags = GNTCOPY_source_gref;

We have gnttab_set_map_op. Should we have gnttap_set_copy_op too?

> -	BUG_ON(ret);
> +	else {
> +		gnttab_batch_copy(vif->tx_copy_ops, nr_cops);
> +		if (nr_mops != 0) {


if (nr_mops) would do.

> +			ret = gnttab_map_refs(vif->tx_map_ops,

So we use gnttab_batch_copy and gnttab_map_refs.

Shouldn't we either use gnttab_batch_copy and gnttab_batch_map or
gnttab_copy gnttab_map_refs. (where gnttab_copy might be a bare
GNTTABOP_copy or might be a helper wrapper).

The point of the batch interface is to handle page unsharing etc, but
doing it only for copies seems like a waste one way or another.

#include <paul's-comments>

Ian.

Re: [PATCH net-next v2 2/2] xen-netback: Grant copy the header instead of map and memcpy

[Ian Campbell]

On Mon, 2014-03-31 at 16:08 +0100, Zoltan Kiss wrote:
>  
>  check_frags:
> -	for (i = start; i < nr_frags; i++) {
> +	for (i = 0; i < nr_frags; i++, gop_map++) {
>  		int j, newerr;
>  
>  		pending_idx = frag_get_pending_idx(&shinfo->frags[i]);
> -		tx_info = &vif->pending_tx_info[pending_idx];
>  
>  		/* Check error status: if okay then remember grant handle. */
> -		newerr = (++gop_map)->status;
> +		newerr = (gop_map)->status;

You've reworked the handling of gop_map and when and where it is
incremented, which might be a legit cleanup but does it relate to the
bulk of this change somehow that I'm missing?

>  [...] 
>  		__skb_put(skb, data_len);
> +		vif->tx_copy_ops[*copy_ops].source.u.ref = txreq.gref;
> +		vif->tx_copy_ops[*copy_ops].source.domid = vif->domid;
> +		vif->tx_copy_ops[*copy_ops].source.offset = txreq.offset;
> +
> +		vif->tx_copy_ops[*copy_ops].dest.u.gmfn =
> +			virt_to_mfn(skb->data);
> +		vif->tx_copy_ops[*copy_ops].dest.domid = DOMID_SELF;
> +		vif->tx_copy_ops[*copy_ops].dest.offset =
> +			offset_in_page(skb->data);
> +
> +		vif->tx_copy_ops[*copy_ops].len = data_len;
> +		vif->tx_copy_ops[*copy_ops].flags = GNTCOPY_source_gref;

We have gnttab_set_map_op. Should we have gnttap_set_copy_op too?

> -	BUG_ON(ret);
> +	else {
> +		gnttab_batch_copy(vif->tx_copy_ops, nr_cops);
> +		if (nr_mops != 0) {


if (nr_mops) would do.

> +			ret = gnttab_map_refs(vif->tx_map_ops,

So we use gnttab_batch_copy and gnttab_map_refs.

Shouldn't we either use gnttab_batch_copy and gnttab_batch_map or
gnttab_copy gnttab_map_refs. (where gnttab_copy might be a bare
GNTTABOP_copy or might be a helper wrapper).

The point of the batch interface is to handle page unsharing etc, but
doing it only for copies seems like a waste one way or another.

#include <paul's-comments>

Ian.

Re: [PATCH net-next v2 2/2] xen-netback: Grant copy the header instead of map and memcpy

[Zoltan Kiss]

On 01/04/14 10:40, Paul Durrant wrote:
>> diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-
>> netback/netback.c
>> index e781366..ba11ff5 100644
>> --- a/drivers/net/xen-netback/netback.c
>> +++ b/drivers/net/xen-netback/netback.c
>> @@ -915,35 +915,30 @@ static inline void xenvif_grant_handle_reset(struct
>> xenvif *vif,
>>
>>   static int xenvif_tx_check_gop(struct xenvif *vif,
>>   			       struct sk_buff *skb,
>> -			       struct gnttab_map_grant_ref **gopp_map)
>> +			       struct gnttab_map_grant_ref **gopp_map,
>> +			       struct gnttab_copy **gopp_copy)
>>   {
>>   	struct gnttab_map_grant_ref *gop_map = *gopp_map;
>>   	u16 pending_idx = XENVIF_TX_CB(skb)->pending_idx;
>>   	struct skb_shared_info *shinfo = skb_shinfo(skb);
>> -	struct pending_tx_info *tx_info;
>>   	int nr_frags = shinfo->nr_frags;
>> -	int i, err, start;
>> +	int i, err;
>>   	struct sk_buff *first_skb = NULL;
>>
>>   	/* Check status of header. */
>> -	err = gop_map->status;
>> +	err = (*gopp_copy)->status;
>> +	(*gopp_copy)++;
>
> I guess there's no undo work in the case of a copy op so you can bump the copy count here, but it might have been nicer to pair it with the update to the map count.
I rather prefer to group related operations on the same variable to stay 
close to each other.


>> @@ -1067,9 +1051,9 @@ static int xenvif_get_extras(struct xenvif *vif,
>>
>>   		memcpy(&extra, RING_GET_REQUEST(&vif->tx, cons),
>>   		       sizeof(extra));
>> +		vif->tx.req_cons = ++cons;
>>   		if (unlikely(!extra.type ||
>>   			     extra.type >= XEN_NETIF_EXTRA_TYPE_MAX)) {
>> -			vif->tx.req_cons = ++cons;
>>   			netdev_err(vif->dev,
>>   				   "Invalid extra type: %d\n", extra.type);
>>   			xenvif_fatal_tx_err(vif);
>> @@ -1077,7 +1061,6 @@ static int xenvif_get_extras(struct xenvif *vif,
>>   		}
>>
>>   		memcpy(&extras[extra.type - 1], &extra, sizeof(extra));
>> -		vif->tx.req_cons = ++cons;
>
> I know you called this out as unrelated, but I still think it would be better in a separate patch.
Ok


>> @@ -1269,24 +1255,39 @@ static unsigned xenvif_tx_build_gops(struct
>> xenvif *vif, int budget)
>>   			}
>>   		}
>>
>> -		xenvif_tx_create_gop(vif, pending_idx, &txreq, gop);
>> -
>> -		gop++;
>> -
>>   		XENVIF_TX_CB(skb)->pending_idx = pending_idx;
>>
>>   		__skb_put(skb, data_len);
>> +		vif->tx_copy_ops[*copy_ops].source.u.ref = txreq.gref;
>> +		vif->tx_copy_ops[*copy_ops].source.domid = vif->domid;
>> +		vif->tx_copy_ops[*copy_ops].source.offset = txreq.offset;
>> +
>> +		vif->tx_copy_ops[*copy_ops].dest.u.gmfn =
>> +			virt_to_mfn(skb->data);
>> +		vif->tx_copy_ops[*copy_ops].dest.domid = DOMID_SELF;
>> +		vif->tx_copy_ops[*copy_ops].dest.offset =
>> +			offset_in_page(skb->data);
>> +
>> +		vif->tx_copy_ops[*copy_ops].len = data_len;
>> +		vif->tx_copy_ops[*copy_ops].flags =
>> GNTCOPY_source_gref;
>> +
>> +		(*copy_ops)++;
>>
>>   		skb_shinfo(skb)->nr_frags = ret;
>>   		if (data_len < txreq.size) {
>>   			skb_shinfo(skb)->nr_frags++;
>>   			frag_set_pending_idx(&skb_shinfo(skb)->frags[0],
>>   					     pending_idx);
>> +			xenvif_tx_create_gop(vif, pending_idx, &txreq,
>> gop);
>> +			gop++;
>>   		} else {
>>   			frag_set_pending_idx(&skb_shinfo(skb)->frags[0],
>>   					     INVALID_PENDING_IDX);
>> +			memcpy(&vif->pending_tx_info[pending_idx].req,
>> &txreq,
>> +			       sizeof(txreq));
>>   		}
>>
>> +
>
> Unnecessary whitespace change.
Ok

>
>>   		vif->pending_cons++;
>>
>>   		request_gop = xenvif_get_requests(vif, skb, txfrags, gop);
>> @@ -1301,11 +1302,13 @@ static unsigned xenvif_tx_build_gops(struct
>> xenvif *vif, int budget)
>>
>>   		vif->tx.req_cons = idx;
>>
>> -		if ((gop-vif->tx_map_ops) >= ARRAY_SIZE(vif-
>>> tx_map_ops))
>> +		if (((gop-vif->tx_map_ops) >= ARRAY_SIZE(vif-
>>> tx_map_ops)) ||
>> +		    (*copy_ops >= ARRAY_SIZE(vif->tx_map_ops)))
>
> Do you mean ARRAY_SIZE(vif->tx_copy_ops) here?
Yes, I'll correct it.

>
>>   			break;
>>   	}
>>
>> -	return gop - vif->tx_map_ops;
>> +	(*map_ops) = gop - vif->tx_map_ops;
>> +	return;
>>   }
>>
>>   /* Consolidate skb with a frag_list into a brand new one with local pages on
>> @@ -1377,6 +1380,7 @@ static int xenvif_handle_frag_list(struct xenvif *vif,
>> struct sk_buff *skb)
>>   static int xenvif_tx_submit(struct xenvif *vif)
>>   {
>>   	struct gnttab_map_grant_ref *gop_map = vif->tx_map_ops;
>> +	struct gnttab_copy *gop_copy = vif->tx_copy_ops;
>>   	struct sk_buff *skb;
>>   	int work_done = 0;
>>
>> @@ -1389,7 +1393,7 @@ static int xenvif_tx_submit(struct xenvif *vif)
>>   		txp = &vif->pending_tx_info[pending_idx].req;
>>
>>   		/* Check the remap error code. */
>> -		if (unlikely(xenvif_tx_check_gop(vif, skb, &gop_map))) {
>> +		if (unlikely(xenvif_tx_check_gop(vif, skb, &gop_map,
>> &gop_copy))) {
>>   			netdev_dbg(vif->dev, "netback grant failed.\n");
>
> It could have been the copy that failed. You should probably change the error message.
I've changed it to "netback grant op failed.\n"

>> @@ -1588,22 +1588,26 @@ static inline void xenvif_tx_dealloc_action(struct
>> xenvif *vif)
>>   /* Called after netfront has transmitted */
>>   int xenvif_tx_action(struct xenvif *vif, int budget)
>>   {
>> -	unsigned nr_mops;
>> +	unsigned nr_mops, nr_cops = 0;
>>   	int work_done, ret;
>>
>>   	if (unlikely(!tx_work_todo(vif)))
>>   		return 0;
>>
>> -	nr_mops = xenvif_tx_build_gops(vif, budget);
>> +	xenvif_tx_build_gops(vif, budget, &nr_cops, &nr_mops);
>>
>> -	if (nr_mops == 0)
>> +	if (nr_cops == 0)
>>   		return 0;
>> -
>> -	ret = gnttab_map_refs(vif->tx_map_ops,
>> -			      NULL,
>> -			      vif->pages_to_map,
>> -			      nr_mops);
>> -	BUG_ON(ret);
>> +	else {
>
> Do you need an 'else' here? Unless I'm misreading the diff your previous clause returns.
Indeed, it's not necessary there

Re: [PATCH net-next v2 2/2] xen-netback: Grant copy the header instead of map and memcpy

[Zoltan Kiss]

On 01/04/14 10:40, Paul Durrant wrote:
>> diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-
>> netback/netback.c
>> index e781366..ba11ff5 100644
>> --- a/drivers/net/xen-netback/netback.c
>> +++ b/drivers/net/xen-netback/netback.c
>> @@ -915,35 +915,30 @@ static inline void xenvif_grant_handle_reset(struct
>> xenvif *vif,
>>
>>   static int xenvif_tx_check_gop(struct xenvif *vif,
>>   			       struct sk_buff *skb,
>> -			       struct gnttab_map_grant_ref **gopp_map)
>> +			       struct gnttab_map_grant_ref **gopp_map,
>> +			       struct gnttab_copy **gopp_copy)
>>   {
>>   	struct gnttab_map_grant_ref *gop_map = *gopp_map;
>>   	u16 pending_idx = XENVIF_TX_CB(skb)->pending_idx;
>>   	struct skb_shared_info *shinfo = skb_shinfo(skb);
>> -	struct pending_tx_info *tx_info;
>>   	int nr_frags = shinfo->nr_frags;
>> -	int i, err, start;
>> +	int i, err;
>>   	struct sk_buff *first_skb = NULL;
>>
>>   	/* Check status of header. */
>> -	err = gop_map->status;
>> +	err = (*gopp_copy)->status;
>> +	(*gopp_copy)++;
>
> I guess there's no undo work in the case of a copy op so you can bump the copy count here, but it might have been nicer to pair it with the update to the map count.
I rather prefer to group related operations on the same variable to stay 
close to each other.


>> @@ -1067,9 +1051,9 @@ static int xenvif_get_extras(struct xenvif *vif,
>>
>>   		memcpy(&extra, RING_GET_REQUEST(&vif->tx, cons),
>>   		       sizeof(extra));
>> +		vif->tx.req_cons = ++cons;
>>   		if (unlikely(!extra.type ||
>>   			     extra.type >= XEN_NETIF_EXTRA_TYPE_MAX)) {
>> -			vif->tx.req_cons = ++cons;
>>   			netdev_err(vif->dev,
>>   				   "Invalid extra type: %d\n", extra.type);
>>   			xenvif_fatal_tx_err(vif);
>> @@ -1077,7 +1061,6 @@ static int xenvif_get_extras(struct xenvif *vif,
>>   		}
>>
>>   		memcpy(&extras[extra.type - 1], &extra, sizeof(extra));
>> -		vif->tx.req_cons = ++cons;
>
> I know you called this out as unrelated, but I still think it would be better in a separate patch.
Ok


>> @@ -1269,24 +1255,39 @@ static unsigned xenvif_tx_build_gops(struct
>> xenvif *vif, int budget)
>>   			}
>>   		}
>>
>> -		xenvif_tx_create_gop(vif, pending_idx, &txreq, gop);
>> -
>> -		gop++;
>> -
>>   		XENVIF_TX_CB(skb)->pending_idx = pending_idx;
>>
>>   		__skb_put(skb, data_len);
>> +		vif->tx_copy_ops[*copy_ops].source.u.ref = txreq.gref;
>> +		vif->tx_copy_ops[*copy_ops].source.domid = vif->domid;
>> +		vif->tx_copy_ops[*copy_ops].source.offset = txreq.offset;
>> +
>> +		vif->tx_copy_ops[*copy_ops].dest.u.gmfn =
>> +			virt_to_mfn(skb->data);
>> +		vif->tx_copy_ops[*copy_ops].dest.domid = DOMID_SELF;
>> +		vif->tx_copy_ops[*copy_ops].dest.offset =
>> +			offset_in_page(skb->data);
>> +
>> +		vif->tx_copy_ops[*copy_ops].len = data_len;
>> +		vif->tx_copy_ops[*copy_ops].flags =
>> GNTCOPY_source_gref;
>> +
>> +		(*copy_ops)++;
>>
>>   		skb_shinfo(skb)->nr_frags = ret;
>>   		if (data_len < txreq.size) {
>>   			skb_shinfo(skb)->nr_frags++;
>>   			frag_set_pending_idx(&skb_shinfo(skb)->frags[0],
>>   					     pending_idx);
>> +			xenvif_tx_create_gop(vif, pending_idx, &txreq,
>> gop);
>> +			gop++;
>>   		} else {
>>   			frag_set_pending_idx(&skb_shinfo(skb)->frags[0],
>>   					     INVALID_PENDING_IDX);
>> +			memcpy(&vif->pending_tx_info[pending_idx].req,
>> &txreq,
>> +			       sizeof(txreq));
>>   		}
>>
>> +
>
> Unnecessary whitespace change.
Ok

>
>>   		vif->pending_cons++;
>>
>>   		request_gop = xenvif_get_requests(vif, skb, txfrags, gop);
>> @@ -1301,11 +1302,13 @@ static unsigned xenvif_tx_build_gops(struct
>> xenvif *vif, int budget)
>>
>>   		vif->tx.req_cons = idx;
>>
>> -		if ((gop-vif->tx_map_ops) >= ARRAY_SIZE(vif-
>>> tx_map_ops))
>> +		if (((gop-vif->tx_map_ops) >= ARRAY_SIZE(vif-
>>> tx_map_ops)) ||
>> +		    (*copy_ops >= ARRAY_SIZE(vif->tx_map_ops)))
>
> Do you mean ARRAY_SIZE(vif->tx_copy_ops) here?
Yes, I'll correct it.

>
>>   			break;
>>   	}
>>
>> -	return gop - vif->tx_map_ops;
>> +	(*map_ops) = gop - vif->tx_map_ops;
>> +	return;
>>   }
>>
>>   /* Consolidate skb with a frag_list into a brand new one with local pages on
>> @@ -1377,6 +1380,7 @@ static int xenvif_handle_frag_list(struct xenvif *vif,
>> struct sk_buff *skb)
>>   static int xenvif_tx_submit(struct xenvif *vif)
>>   {
>>   	struct gnttab_map_grant_ref *gop_map = vif->tx_map_ops;
>> +	struct gnttab_copy *gop_copy = vif->tx_copy_ops;
>>   	struct sk_buff *skb;
>>   	int work_done = 0;
>>
>> @@ -1389,7 +1393,7 @@ static int xenvif_tx_submit(struct xenvif *vif)
>>   		txp = &vif->pending_tx_info[pending_idx].req;
>>
>>   		/* Check the remap error code. */
>> -		if (unlikely(xenvif_tx_check_gop(vif, skb, &gop_map))) {
>> +		if (unlikely(xenvif_tx_check_gop(vif, skb, &gop_map,
>> &gop_copy))) {
>>   			netdev_dbg(vif->dev, "netback grant failed.\n");
>
> It could have been the copy that failed. You should probably change the error message.
I've changed it to "netback grant op failed.\n"

>> @@ -1588,22 +1588,26 @@ static inline void xenvif_tx_dealloc_action(struct
>> xenvif *vif)
>>   /* Called after netfront has transmitted */
>>   int xenvif_tx_action(struct xenvif *vif, int budget)
>>   {
>> -	unsigned nr_mops;
>> +	unsigned nr_mops, nr_cops = 0;
>>   	int work_done, ret;
>>
>>   	if (unlikely(!tx_work_todo(vif)))
>>   		return 0;
>>
>> -	nr_mops = xenvif_tx_build_gops(vif, budget);
>> +	xenvif_tx_build_gops(vif, budget, &nr_cops, &nr_mops);
>>
>> -	if (nr_mops == 0)
>> +	if (nr_cops == 0)
>>   		return 0;
>> -
>> -	ret = gnttab_map_refs(vif->tx_map_ops,
>> -			      NULL,
>> -			      vif->pages_to_map,
>> -			      nr_mops);
>> -	BUG_ON(ret);
>> +	else {
>
> Do you need an 'else' here? Unless I'm misreading the diff your previous clause returns.
Indeed, it's not necessary there

Re: [PATCH net-next v2 2/2] xen-netback: Grant copy the header instead of map and memcpy

[Zoltan Kiss]

On 01/04/14 12:40, Ian Campbell wrote:
> On Mon, 2014-03-31 at 16:08 +0100, Zoltan Kiss wrote:
>>
>>   check_frags:
>> -	for (i = start; i < nr_frags; i++) {
>> +	for (i = 0; i < nr_frags; i++, gop_map++) {
>>   		int j, newerr;
>>
>>   		pending_idx = frag_get_pending_idx(&shinfo->frags[i]);
>> -		tx_info = &vif->pending_tx_info[pending_idx];
>>
>>   		/* Check error status: if okay then remember grant handle. */
>> -		newerr = (++gop_map)->status;
>> +		newerr = (gop_map)->status;
>
> You've reworked the handling of gop_map and when and where it is
> incremented, which might be a legit cleanup but does it relate to the
> bulk of this change somehow that I'm missing?
That original "++gop_map" assumed the header was also grant mapped, and 
incremented the pointer first here, which is wrong now.

>
>>   [...]
>>   		__skb_put(skb, data_len);
>> +		vif->tx_copy_ops[*copy_ops].source.u.ref = txreq.gref;
>> +		vif->tx_copy_ops[*copy_ops].source.domid = vif->domid;
>> +		vif->tx_copy_ops[*copy_ops].source.offset = txreq.offset;
>> +
>> +		vif->tx_copy_ops[*copy_ops].dest.u.gmfn =
>> +			virt_to_mfn(skb->data);
>> +		vif->tx_copy_ops[*copy_ops].dest.domid = DOMID_SELF;
>> +		vif->tx_copy_ops[*copy_ops].dest.offset =
>> +			offset_in_page(skb->data);
>> +
>> +		vif->tx_copy_ops[*copy_ops].len = data_len;
>> +		vif->tx_copy_ops[*copy_ops].flags = GNTCOPY_source_gref;
>
> We have gnttab_set_map_op. Should we have gnttap_set_copy_op too?
This is the only place at the moment when we do this, so I wouldn't 
bother to do it.

>
>> -	BUG_ON(ret);
>> +	else {
>> +		gnttab_batch_copy(vif->tx_copy_ops, nr_cops);
>> +		if (nr_mops != 0) {
>
>
> if (nr_mops) would do.
>
>> +			ret = gnttab_map_refs(vif->tx_map_ops,
>
> So we use gnttab_batch_copy and gnttab_map_refs.
>
> Shouldn't we either use gnttab_batch_copy and gnttab_batch_map or
> gnttab_copy gnttab_map_refs. (where gnttab_copy might be a bare
> GNTTABOP_copy or might be a helper wrapper).
>
> The point of the batch interface is to handle page unsharing etc, but
> doing it only for copies seems like a waste one way or another.
The difference between gnttab_batch_map and gnttab_map_refs is that the 
latter calls set_foreign_p2m_mapping, which we need for sure.
gnttab_batch_copy calls the hypercall and tries again if op->status == 
GNTST_eagain. I think that's exactly what we need here as well.
The naming might be confusing indeed, but that should be the topic of an 
another patch.

Zoli

Re: [PATCH net-next v2 2/2] xen-netback: Grant copy the header instead of map and memcpy

[Zoltan Kiss]

On 01/04/14 12:40, Ian Campbell wrote:
> On Mon, 2014-03-31 at 16:08 +0100, Zoltan Kiss wrote:
>>
>>   check_frags:
>> -	for (i = start; i < nr_frags; i++) {
>> +	for (i = 0; i < nr_frags; i++, gop_map++) {
>>   		int j, newerr;
>>
>>   		pending_idx = frag_get_pending_idx(&shinfo->frags[i]);
>> -		tx_info = &vif->pending_tx_info[pending_idx];
>>
>>   		/* Check error status: if okay then remember grant handle. */
>> -		newerr = (++gop_map)->status;
>> +		newerr = (gop_map)->status;
>
> You've reworked the handling of gop_map and when and where it is
> incremented, which might be a legit cleanup but does it relate to the
> bulk of this change somehow that I'm missing?
That original "++gop_map" assumed the header was also grant mapped, and 
incremented the pointer first here, which is wrong now.

>
>>   [...]
>>   		__skb_put(skb, data_len);
>> +		vif->tx_copy_ops[*copy_ops].source.u.ref = txreq.gref;
>> +		vif->tx_copy_ops[*copy_ops].source.domid = vif->domid;
>> +		vif->tx_copy_ops[*copy_ops].source.offset = txreq.offset;
>> +
>> +		vif->tx_copy_ops[*copy_ops].dest.u.gmfn =
>> +			virt_to_mfn(skb->data);
>> +		vif->tx_copy_ops[*copy_ops].dest.domid = DOMID_SELF;
>> +		vif->tx_copy_ops[*copy_ops].dest.offset =
>> +			offset_in_page(skb->data);
>> +
>> +		vif->tx_copy_ops[*copy_ops].len = data_len;
>> +		vif->tx_copy_ops[*copy_ops].flags = GNTCOPY_source_gref;
>
> We have gnttab_set_map_op. Should we have gnttap_set_copy_op too?
This is the only place at the moment when we do this, so I wouldn't 
bother to do it.

>
>> -	BUG_ON(ret);
>> +	else {
>> +		gnttab_batch_copy(vif->tx_copy_ops, nr_cops);
>> +		if (nr_mops != 0) {
>
>
> if (nr_mops) would do.
>
>> +			ret = gnttab_map_refs(vif->tx_map_ops,
>
> So we use gnttab_batch_copy and gnttab_map_refs.
>
> Shouldn't we either use gnttab_batch_copy and gnttab_batch_map or
> gnttab_copy gnttab_map_refs. (where gnttab_copy might be a bare
> GNTTABOP_copy or might be a helper wrapper).
>
> The point of the batch interface is to handle page unsharing etc, but
> doing it only for copies seems like a waste one way or another.
The difference between gnttab_batch_map and gnttab_map_refs is that the 
latter calls set_foreign_p2m_mapping, which we need for sure.
gnttab_batch_copy calls the hypercall and tries again if op->status == 
GNTST_eagain. I think that's exactly what we need here as well.
The naming might be confusing indeed, but that should be the topic of an 
another patch.

Zoli

Re: [PATCH net-next v2 2/2] xen-netback: Grant copy the header instead of map and memcpy

[Ian Campbell]

On Tue, 2014-04-01 at 19:55 +0100, Zoltan Kiss wrote:
> >> @@ -1389,7 +1393,7 @@ static int xenvif_tx_submit(struct xenvif
> *vif)
> >>              txp = &vif->pending_tx_info[pending_idx].req;
> >>
> >>              /* Check the remap error code. */
> >> -            if (unlikely(xenvif_tx_check_gop(vif, skb, &gop_map)))
> {
> >> +            if (unlikely(xenvif_tx_check_gop(vif, skb, &gop_map,
> >> &gop_copy))) {
> >>                      netdev_dbg(vif->dev, "netback grant
> failed.\n");
> >
> > It could have been the copy that failed. You should probably change
> the error message.
> I've changed it to "netback grant op failed.\n"

Perhaps xenvif_tx_check_gop is in a position to log something more
specific about the failure? (maybe it already does, I didn't look).

Ian.

Re: [PATCH net-next v2 2/2] xen-netback: Grant copy the header instead of map and memcpy

[Ian Campbell]

On Tue, 2014-04-01 at 19:55 +0100, Zoltan Kiss wrote:
> >> @@ -1389,7 +1393,7 @@ static int xenvif_tx_submit(struct xenvif
> *vif)
> >>              txp = &vif->pending_tx_info[pending_idx].req;
> >>
> >>              /* Check the remap error code. */
> >> -            if (unlikely(xenvif_tx_check_gop(vif, skb, &gop_map)))
> {
> >> +            if (unlikely(xenvif_tx_check_gop(vif, skb, &gop_map,
> >> &gop_copy))) {
> >>                      netdev_dbg(vif->dev, "netback grant
> failed.\n");
> >
> > It could have been the copy that failed. You should probably change
> the error message.
> I've changed it to "netback grant op failed.\n"

Perhaps xenvif_tx_check_gop is in a position to log something more
specific about the failure? (maybe it already does, I didn't look).

Ian.

Re: [PATCH net-next v2 2/2] xen-netback: Grant copy the header instead of map and memcpy

[Ian Campbell]

On Tue, 2014-04-01 at 20:09 +0100, Zoltan Kiss wrote:
> On 01/04/14 12:40, Ian Campbell wrote:
> > On Mon, 2014-03-31 at 16:08 +0100, Zoltan Kiss wrote:
> >>
> >>   check_frags:
> >> -	for (i = start; i < nr_frags; i++) {
> >> +	for (i = 0; i < nr_frags; i++, gop_map++) {
> >>   		int j, newerr;
> >>
> >>   		pending_idx = frag_get_pending_idx(&shinfo->frags[i]);
> >> -		tx_info = &vif->pending_tx_info[pending_idx];
> >>
> >>   		/* Check error status: if okay then remember grant handle. */
> >> -		newerr = (++gop_map)->status;
> >> +		newerr = (gop_map)->status;
> >
> > You've reworked the handling of gop_map and when and where it is
> > incremented, which might be a legit cleanup but does it relate to the
> > bulk of this change somehow that I'm missing?
> That original "++gop_map" assumed the header was also grant mapped, and 
> incremented the pointer first here, which is wrong now.

OK, that makes sense.

> >>   [...]
> >>   		__skb_put(skb, data_len);
> >> +		vif->tx_copy_ops[*copy_ops].source.u.ref = txreq.gref;
> >> +		vif->tx_copy_ops[*copy_ops].source.domid = vif->domid;
> >> +		vif->tx_copy_ops[*copy_ops].source.offset = txreq.offset;
> >> +
> >> +		vif->tx_copy_ops[*copy_ops].dest.u.gmfn =
> >> +			virt_to_mfn(skb->data);
> >> +		vif->tx_copy_ops[*copy_ops].dest.domid = DOMID_SELF;
> >> +		vif->tx_copy_ops[*copy_ops].dest.offset =
> >> +			offset_in_page(skb->data);
> >> +
> >> +		vif->tx_copy_ops[*copy_ops].len = data_len;
> >> +		vif->tx_copy_ops[*copy_ops].flags = GNTCOPY_source_gref;
> >
> > We have gnttab_set_map_op. Should we have gnttap_set_copy_op too?
> This is the only place at the moment when we do this, so I wouldn't 
> bother to do it.

It's not only about multiple uses of the pattern but about code clarity
and API consistency.

> >> -	BUG_ON(ret);
> >> +	else {
> >> +		gnttab_batch_copy(vif->tx_copy_ops, nr_cops);
> >> +		if (nr_mops != 0) {
> >
> >
> > if (nr_mops) would do.
> >
> >> +			ret = gnttab_map_refs(vif->tx_map_ops,
> >
> > So we use gnttab_batch_copy and gnttab_map_refs.
> >
> > Shouldn't we either use gnttab_batch_copy and gnttab_batch_map or
> > gnttab_copy gnttab_map_refs. (where gnttab_copy might be a bare
> > GNTTABOP_copy or might be a helper wrapper).
> >
> > The point of the batch interface is to handle page unsharing etc, but
> > doing it only for copies seems like a waste one way or another.
> The difference between gnttab_batch_map and gnttab_map_refs is that the 
> latter calls set_foreign_p2m_mapping, which we need for sure.
> gnttab_batch_copy calls the hypercall and tries again if op->status == 
> GNTST_eagain. I think that's exactly what we need here as well.
> The naming might be confusing indeed, but that should be the topic of an 
> another patch.

Whether you choose to do it now or later this code should use a
consistent set of ops, either gnttab_batch_* or gnttab_*_refs, from day
one.

Ian.

Re: [PATCH net-next v2 2/2] xen-netback: Grant copy the header instead of map and memcpy

[Ian Campbell]

On Tue, 2014-04-01 at 20:09 +0100, Zoltan Kiss wrote:
> On 01/04/14 12:40, Ian Campbell wrote:
> > On Mon, 2014-03-31 at 16:08 +0100, Zoltan Kiss wrote:
> >>
> >>   check_frags:
> >> -	for (i = start; i < nr_frags; i++) {
> >> +	for (i = 0; i < nr_frags; i++, gop_map++) {
> >>   		int j, newerr;
> >>
> >>   		pending_idx = frag_get_pending_idx(&shinfo->frags[i]);
> >> -		tx_info = &vif->pending_tx_info[pending_idx];
> >>
> >>   		/* Check error status: if okay then remember grant handle. */
> >> -		newerr = (++gop_map)->status;
> >> +		newerr = (gop_map)->status;
> >
> > You've reworked the handling of gop_map and when and where it is
> > incremented, which might be a legit cleanup but does it relate to the
> > bulk of this change somehow that I'm missing?
> That original "++gop_map" assumed the header was also grant mapped, and 
> incremented the pointer first here, which is wrong now.

OK, that makes sense.

> >>   [...]
> >>   		__skb_put(skb, data_len);
> >> +		vif->tx_copy_ops[*copy_ops].source.u.ref = txreq.gref;
> >> +		vif->tx_copy_ops[*copy_ops].source.domid = vif->domid;
> >> +		vif->tx_copy_ops[*copy_ops].source.offset = txreq.offset;
> >> +
> >> +		vif->tx_copy_ops[*copy_ops].dest.u.gmfn =
> >> +			virt_to_mfn(skb->data);
> >> +		vif->tx_copy_ops[*copy_ops].dest.domid = DOMID_SELF;
> >> +		vif->tx_copy_ops[*copy_ops].dest.offset =
> >> +			offset_in_page(skb->data);
> >> +
> >> +		vif->tx_copy_ops[*copy_ops].len = data_len;
> >> +		vif->tx_copy_ops[*copy_ops].flags = GNTCOPY_source_gref;
> >
> > We have gnttab_set_map_op. Should we have gnttap_set_copy_op too?
> This is the only place at the moment when we do this, so I wouldn't 
> bother to do it.

It's not only about multiple uses of the pattern but about code clarity
and API consistency.

> >> -	BUG_ON(ret);
> >> +	else {
> >> +		gnttab_batch_copy(vif->tx_copy_ops, nr_cops);
> >> +		if (nr_mops != 0) {
> >
> >
> > if (nr_mops) would do.
> >
> >> +			ret = gnttab_map_refs(vif->tx_map_ops,
> >
> > So we use gnttab_batch_copy and gnttab_map_refs.
> >
> > Shouldn't we either use gnttab_batch_copy and gnttab_batch_map or
> > gnttab_copy gnttab_map_refs. (where gnttab_copy might be a bare
> > GNTTABOP_copy or might be a helper wrapper).
> >
> > The point of the batch interface is to handle page unsharing etc, but
> > doing it only for copies seems like a waste one way or another.
> The difference between gnttab_batch_map and gnttab_map_refs is that the 
> latter calls set_foreign_p2m_mapping, which we need for sure.
> gnttab_batch_copy calls the hypercall and tries again if op->status == 
> GNTST_eagain. I think that's exactly what we need here as well.
> The naming might be confusing indeed, but that should be the topic of an 
> another patch.

Whether you choose to do it now or later this code should use a
consistent set of ops, either gnttab_batch_* or gnttab_*_refs, from day
one.

Ian.

Re: [Xen-devel] [PATCH net-next v2 2/2] xen-netback: Grant copy the header instead of map and memcpy

[David Vrabel]

On 01/04/14 12:40, Ian Campbell wrote:
> On Mon, 2014-03-31 at 16:08 +0100, Zoltan Kiss wrote:
>>  
>>  		__skb_put(skb, data_len);
>> +		vif->tx_copy_ops[*copy_ops].source.u.ref = txreq.gref;
>> +		vif->tx_copy_ops[*copy_ops].source.domid = vif->domid;
>> +		vif->tx_copy_ops[*copy_ops].source.offset = txreq.offset;
>> +
>> +		vif->tx_copy_ops[*copy_ops].dest.u.gmfn =
>> +			virt_to_mfn(skb->data);
>> +		vif->tx_copy_ops[*copy_ops].dest.domid = DOMID_SELF;
>> +		vif->tx_copy_ops[*copy_ops].dest.offset =
>> +			offset_in_page(skb->data);
>> +
>> +		vif->tx_copy_ops[*copy_ops].len = data_len;
>> +		vif->tx_copy_ops[*copy_ops].flags = GNTCOPY_source_gref;
> 
> We have gnttab_set_map_op. Should we have gnttap_set_copy_op too?

A set of 3 might be useful I think.

gnttab_set_copy_op_ref_to_gfn()
gnttab_set_copy_op_gfn_to_ref()
gnttab_set_copy_op_ref_to_ref()

> 
>> -	BUG_ON(ret);
>> +	else {
>> +		gnttab_batch_copy(vif->tx_copy_ops, nr_cops);
>> +		if (nr_mops != 0) {
> 
> 
> if (nr_mops) would do.
> 
>> +			ret = gnttab_map_refs(vif->tx_map_ops,
> 
> So we use gnttab_batch_copy and gnttab_map_refs.
> 
> Shouldn't we either use gnttab_batch_copy and gnttab_batch_map or
> gnttab_copy gnttab_map_refs. (where gnttab_copy might be a bare
> GNTTABOP_copy or might be a helper wrapper).

gnttab_batch_map() is not correct here since it does not update the p2m.
 There is only one copy API (gnttab_batch_copy()).

> The point of the batch interface is to handle page unsharing etc, but
> doing it only for copies seems like a waste one way or another.

Both mapping and copy need to handle (hypervisor) paging/shaing and the
two calls Zoli has used do this.

gnttab_map_refs() is basically gnttab_batch_map() +
set_foreign_p2m_mapping().

I'd be in favour of a patch that:

- renamed gnttab_map_refs() to gnttab_batch_map_pages()
- refactored it to call gnttab_batch_map().
- added documentation

But I don't see why this would be a prerequisite for this series.

David

Re: [PATCH net-next v2 2/2] xen-netback: Grant copy the header instead of map and memcpy

[David Vrabel]

On 01/04/14 12:40, Ian Campbell wrote:
> On Mon, 2014-03-31 at 16:08 +0100, Zoltan Kiss wrote:
>>  
>>  		__skb_put(skb, data_len);
>> +		vif->tx_copy_ops[*copy_ops].source.u.ref = txreq.gref;
>> +		vif->tx_copy_ops[*copy_ops].source.domid = vif->domid;
>> +		vif->tx_copy_ops[*copy_ops].source.offset = txreq.offset;
>> +
>> +		vif->tx_copy_ops[*copy_ops].dest.u.gmfn =
>> +			virt_to_mfn(skb->data);
>> +		vif->tx_copy_ops[*copy_ops].dest.domid = DOMID_SELF;
>> +		vif->tx_copy_ops[*copy_ops].dest.offset =
>> +			offset_in_page(skb->data);
>> +
>> +		vif->tx_copy_ops[*copy_ops].len = data_len;
>> +		vif->tx_copy_ops[*copy_ops].flags = GNTCOPY_source_gref;
> 
> We have gnttab_set_map_op. Should we have gnttap_set_copy_op too?

A set of 3 might be useful I think.

gnttab_set_copy_op_ref_to_gfn()
gnttab_set_copy_op_gfn_to_ref()
gnttab_set_copy_op_ref_to_ref()

> 
>> -	BUG_ON(ret);
>> +	else {
>> +		gnttab_batch_copy(vif->tx_copy_ops, nr_cops);
>> +		if (nr_mops != 0) {
> 
> 
> if (nr_mops) would do.
> 
>> +			ret = gnttab_map_refs(vif->tx_map_ops,
> 
> So we use gnttab_batch_copy and gnttab_map_refs.
> 
> Shouldn't we either use gnttab_batch_copy and gnttab_batch_map or
> gnttab_copy gnttab_map_refs. (where gnttab_copy might be a bare
> GNTTABOP_copy or might be a helper wrapper).

gnttab_batch_map() is not correct here since it does not update the p2m.
 There is only one copy API (gnttab_batch_copy()).

> The point of the batch interface is to handle page unsharing etc, but
> doing it only for copies seems like a waste one way or another.

Both mapping and copy need to handle (hypervisor) paging/shaing and the
two calls Zoli has used do this.

gnttab_map_refs() is basically gnttab_batch_map() +
set_foreign_p2m_mapping().

I'd be in favour of a patch that:

- renamed gnttab_map_refs() to gnttab_batch_map_pages()
- refactored it to call gnttab_batch_map().
- added documentation

But I don't see why this would be a prerequisite for this series.

David

Re: [Xen-devel] [PATCH net-next v2 2/2] xen-netback: Grant copy the header instead of map and memcpy

[Ian Campbell]

On Wed, 2014-04-02 at 14:11 +0100, David Vrabel wrote:

> I'd be in favour of a patch that:
> 
> - renamed gnttab_map_refs() to gnttab_batch_map_pages()
> - refactored it to call gnttab_batch_map().
> - added documentation
> 
> But I don't see why this would be a prerequisite for this series.

No, I think I misunderstoopd the API (because it is confusingly
named...)
> 
> David

Re: [PATCH net-next v2 2/2] xen-netback: Grant copy the header instead of map and memcpy

[Ian Campbell]

On Wed, 2014-04-02 at 14:11 +0100, David Vrabel wrote:

> I'd be in favour of a patch that:
> 
> - renamed gnttab_map_refs() to gnttab_batch_map_pages()
> - refactored it to call gnttab_batch_map().
> - added documentation
> 
> But I don't see why this would be a prerequisite for this series.

No, I think I misunderstoopd the API (because it is confusingly
named...)
> 
> David

Re: [Xen-devel] [PATCH net-next v2 2/2] xen-netback: Grant copy the header instead of map and memcpy

[Zoltan Kiss]

On 02/04/14 14:11, David Vrabel wrote:
> On 01/04/14 12:40, Ian Campbell wrote:
>> On Mon, 2014-03-31 at 16:08 +0100, Zoltan Kiss wrote:
>>>
>>>   		__skb_put(skb, data_len);
>>> +		vif->tx_copy_ops[*copy_ops].source.u.ref = txreq.gref;
>>> +		vif->tx_copy_ops[*copy_ops].source.domid = vif->domid;
>>> +		vif->tx_copy_ops[*copy_ops].source.offset = txreq.offset;
>>> +
>>> +		vif->tx_copy_ops[*copy_ops].dest.u.gmfn =
>>> +			virt_to_mfn(skb->data);
>>> +		vif->tx_copy_ops[*copy_ops].dest.domid = DOMID_SELF;
>>> +		vif->tx_copy_ops[*copy_ops].dest.offset =
>>> +			offset_in_page(skb->data);
>>> +
>>> +		vif->tx_copy_ops[*copy_ops].len = data_len;
>>> +		vif->tx_copy_ops[*copy_ops].flags = GNTCOPY_source_gref;
>>
>> We have gnttab_set_map_op. Should we have gnttap_set_copy_op too?
>
> A set of 3 might be useful I think.
>
> gnttab_set_copy_op_ref_to_gfn()
> gnttab_set_copy_op_gfn_to_ref()
> gnttab_set_copy_op_ref_to_ref()
I doubt it would increase clarity in any way, but I'll send a patch on 
top of these.

Zoli

Re: [PATCH net-next v2 2/2] xen-netback: Grant copy the header instead of map and memcpy

[Zoltan Kiss]

On 02/04/14 14:11, David Vrabel wrote:
> On 01/04/14 12:40, Ian Campbell wrote:
>> On Mon, 2014-03-31 at 16:08 +0100, Zoltan Kiss wrote:
>>>
>>>   		__skb_put(skb, data_len);
>>> +		vif->tx_copy_ops[*copy_ops].source.u.ref = txreq.gref;
>>> +		vif->tx_copy_ops[*copy_ops].source.domid = vif->domid;
>>> +		vif->tx_copy_ops[*copy_ops].source.offset = txreq.offset;
>>> +
>>> +		vif->tx_copy_ops[*copy_ops].dest.u.gmfn =
>>> +			virt_to_mfn(skb->data);
>>> +		vif->tx_copy_ops[*copy_ops].dest.domid = DOMID_SELF;
>>> +		vif->tx_copy_ops[*copy_ops].dest.offset =
>>> +			offset_in_page(skb->data);
>>> +
>>> +		vif->tx_copy_ops[*copy_ops].len = data_len;
>>> +		vif->tx_copy_ops[*copy_ops].flags = GNTCOPY_source_gref;
>>
>> We have gnttab_set_map_op. Should we have gnttap_set_copy_op too?
>
> A set of 3 might be useful I think.
>
> gnttab_set_copy_op_ref_to_gfn()
> gnttab_set_copy_op_gfn_to_ref()
> gnttab_set_copy_op_ref_to_ref()
I doubt it would increase clarity in any way, but I'll send a patch on 
top of these.

Zoli

[PATCH net-next v2 1/2] xen-netback: Rename map ops

[Zoltan Kiss]

Rename identifiers to state explicitly that they refer to map ops.

Signed-off-by: Zoltan Kiss <zoltan.kiss@citrix.com>
---
diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index 0efa32d..a650899 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -915,9 +915,9 @@ static inline void xenvif_grant_handle_reset(struct xenvif *vif,
 
 static int xenvif_tx_check_gop(struct xenvif *vif,
 			       struct sk_buff *skb,
-			       struct gnttab_map_grant_ref **gopp)
+			       struct gnttab_map_grant_ref **gopp_map)
 {
-	struct gnttab_map_grant_ref *gop = *gopp;
+	struct gnttab_map_grant_ref *gop_map = *gopp_map;
 	u16 pending_idx = XENVIF_TX_CB(skb)->pending_idx;
 	struct skb_shared_info *shinfo = skb_shinfo(skb);
 	struct pending_tx_info *tx_info;
@@ -926,11 +926,11 @@ static int xenvif_tx_check_gop(struct xenvif *vif,
 	struct sk_buff *first_skb = NULL;
 
 	/* Check status of header. */
-	err = gop->status;
+	err = gop_map->status;
 	if (unlikely(err))
 		xenvif_idx_release(vif, pending_idx, XEN_NETIF_RSP_ERROR);
 	else
-		xenvif_grant_handle_set(vif, pending_idx , gop->handle);
+		xenvif_grant_handle_set(vif, pending_idx , gop_map->handle);
 
 	/* Skip first skb fragment if it is on same page as header fragment. */
 	start = (frag_get_pending_idx(&shinfo->frags[0]) == pending_idx);
@@ -943,10 +943,12 @@ check_frags:
 		tx_info = &vif->pending_tx_info[pending_idx];
 
 		/* Check error status: if okay then remember grant handle. */
-		newerr = (++gop)->status;
+		newerr = (++gop_map)->status;
 
 		if (likely(!newerr)) {
-			xenvif_grant_handle_set(vif, pending_idx , gop->handle);
+			xenvif_grant_handle_set(vif,
+						pending_idx,
+						gop_map->handle);
 			/* Had a previous error? Invalidate this fragment. */
 			if (unlikely(err))
 				xenvif_idx_unmap(vif, pending_idx);
@@ -998,7 +1000,7 @@ check_frags:
 		}
 	}
 
-	*gopp = gop + 1;
+	*gopp_map = gop_map + 1;
 	return err;
 }
 
@@ -1374,7 +1376,7 @@ static int xenvif_handle_frag_list(struct xenvif *vif, struct sk_buff *skb)
 
 static int xenvif_tx_submit(struct xenvif *vif)
 {
-	struct gnttab_map_grant_ref *gop = vif->tx_map_ops;
+	struct gnttab_map_grant_ref *gop_map = vif->tx_map_ops;
 	struct sk_buff *skb;
 	int work_done = 0;
 
@@ -1387,7 +1389,7 @@ static int xenvif_tx_submit(struct xenvif *vif)
 		txp = &vif->pending_tx_info[pending_idx].req;
 
 		/* Check the remap error code. */
-		if (unlikely(xenvif_tx_check_gop(vif, skb, &gop))) {
+		if (unlikely(xenvif_tx_check_gop(vif, skb, &gop_map))) {
 			netdev_dbg(vif->dev, "netback grant failed.\n");
 			skb_shinfo(skb)->nr_frags = 0;
 			kfree_skb(skb);
@@ -1586,21 +1588,21 @@ static inline void xenvif_tx_dealloc_action(struct xenvif *vif)
 /* Called after netfront has transmitted */
 int xenvif_tx_action(struct xenvif *vif, int budget)
 {
-	unsigned nr_gops;
+	unsigned nr_mops;
 	int work_done, ret;
 
 	if (unlikely(!tx_work_todo(vif)))
 		return 0;
 
-	nr_gops = xenvif_tx_build_gops(vif, budget);
+	nr_mops = xenvif_tx_build_gops(vif, budget);
 
-	if (nr_gops == 0)
+	if (nr_mops == 0)
 		return 0;
 
 	ret = gnttab_map_refs(vif->tx_map_ops,
 			      NULL,
 			      vif->pages_to_map,
-			      nr_gops);
+			      nr_mops);
 	BUG_ON(ret);
 
 	work_done = xenvif_tx_submit(vif);