[PATCH net-next 0/6 v9] Open vSwitch zercopy upcall optimiziation

[PATCH net-next 0/6 v9] Open vSwitch zercopy upcall optimiziation

[Thomas Graf]

Series implementing a zerocopy method for OVS upcall messages. Based
on top of commit: (''openvswitch: Enable memory mapped Netlink i/o'')

Thomas Graf (6):
  net: Export skb_zerocopy() to zerocopy from one skb to another
  openvswitch: Allow user space to announce ability to accept unaligned
    Netlink messages
  openvswitch: Drop user features if old user space attempted to create
    datapath
  openvswitch: Pass datapath into userspace queue functions
  openvswitch: Use skb_zerocopy() for upcall
  openvswitch: Compute checksum in skb_gso_segment() if needed

 include/linux/skbuff.h               |   3 +
 include/uapi/linux/openvswitch.h     |  14 ++++-
 net/core/skbuff.c                    |  85 ++++++++++++++++++++++++++++
 net/netfilter/nfnetlink_queue_core.c |  59 ++-----------------
 net/openvswitch/datapath.c           | 106 ++++++++++++++++++++++++++---------
 net/openvswitch/datapath.h           |   2 +
 6 files changed, 185 insertions(+), 84 deletions(-)

---
V9: - Dropped patches 1-3 (merged)
    - Dropped skb argument from upcall_msg_size()
    - Dropped dp_ifindex and net argument from all queue functions
    - Added patch to remove NETIF_F_HW_CSUM from __skb_gso_segment()
V8: - Dropped patch adding NLM_F_REPLACE support, I'll pursue this in a
      separate patch series. Addresses Jesse's comments.
    - Improved comment describing OVS_DATAPATH_VERSION bump.
V7: - removed unintential kernel-doc comment
    - WARN_ONCE() -> WARN(), message on single line, added \n
V6: - Added memory mapped netlink i/o support
    - Drop user_features if old user space not aware of user features
      reuses an existing datapath
V5: - Removed padding requirement in user space
    - Added OVS_DP_F_UNALIGNED flag let user space signal ability to
      receive unaligned Netlink messages, fall back to linear copy
      otherwise.
V4: - Daniel Borkmann pointed out that the style in skbuff.h has changed
      in net-next, adapted to no longer using extern in headers.
V3: - Removed unneeded alignment of nlmsg_len after padding
V2: - Added skb_zerocopy_headlen() to calculate headroom of destination
      buffer. This also takes care of the from->head_frag issue.
    - Attribute alignment for frag_list case
    - API documentation
    - performance data for CHECKSUM_PARTIAL tx case

[PATCH net-next 1/6] net: Export skb_zerocopy() to zerocopy from one skb to another

[Thomas Graf]

Make the skb zerocopy logic written for nfnetlink queue available for
use by other modules.

Signed-off-by: Thomas Graf <tgraf@suug.ch>
Reviewed-by: Daniel Borkmann <dborkman@redhat.com>
---
 include/linux/skbuff.h               |  3 ++
 net/core/skbuff.c                    | 85 ++++++++++++++++++++++++++++++++++++
 net/netfilter/nfnetlink_queue_core.c | 59 ++-----------------------
 3 files changed, 92 insertions(+), 55 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 77c7aae..a6781af 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -2363,6 +2363,9 @@ int skb_splice_bits(struct sk_buff *skb, unsigned int offset,
 		    struct pipe_inode_info *pipe, unsigned int len,
 		    unsigned int flags);
 void skb_copy_and_csum_dev(const struct sk_buff *skb, u8 *to);
+unsigned int skb_zerocopy_headlen(const struct sk_buff *from);
+void skb_zerocopy(struct sk_buff *to, const struct sk_buff *from,
+		  int len, int hlen);
 void skb_split(struct sk_buff *skb, struct sk_buff *skb1, const u32 len);
 int skb_shift(struct sk_buff *tgt, struct sk_buff *skb, int shiftlen);
 void skb_scrub_packet(struct sk_buff *skb, bool xnet);
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 06e72d3..63116d7 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -2122,6 +2122,91 @@ __wsum skb_copy_and_csum_bits(const struct sk_buff *skb, int offset,
 }
 EXPORT_SYMBOL(skb_copy_and_csum_bits);
 
+ /**
+ *	skb_zerocopy_headlen - Calculate headroom needed for skb_zerocopy()
+ *	@from: source buffer
+ *
+ *	Calculates the amount of linear headroom needed in the 'to' skb passed
+ *	into skb_zerocopy().
+ */
+unsigned int
+skb_zerocopy_headlen(const struct sk_buff *from)
+{
+	unsigned int hlen = 0;
+
+	if (!from->head_frag ||
+	    skb_headlen(from) < L1_CACHE_BYTES ||
+	    skb_shinfo(from)->nr_frags >= MAX_SKB_FRAGS)
+		hlen = skb_headlen(from);
+
+	if (skb_has_frag_list(from))
+		hlen = from->len;
+
+	return hlen;
+}
+EXPORT_SYMBOL_GPL(skb_zerocopy_headlen);
+
+/**
+ *	skb_zerocopy - Zero copy skb to skb
+ *	@to: destination buffer
+ *	@source: source buffer
+ *	@len: number of bytes to copy from source buffer
+ *	@hlen: size of linear headroom in destination buffer
+ *
+ *	Copies up to `len` bytes from `from` to `to` by creating references
+ *	to the frags in the source buffer.
+ *
+ *	The `hlen` as calculated by skb_zerocopy_headlen() specifies the
+ *	headroom in the `to` buffer.
+ */
+void
+skb_zerocopy(struct sk_buff *to, const struct sk_buff *from, int len, int hlen)
+{
+	int i, j = 0;
+	int plen = 0; /* length of skb->head fragment */
+	struct page *page;
+	unsigned int offset;
+
+	BUG_ON(!from->head_frag && !hlen);
+
+	/* dont bother with small payloads */
+	if (len <= skb_tailroom(to)) {
+		skb_copy_bits(from, 0, skb_put(to, len), len);
+		return;
+	}
+
+	if (hlen) {
+		skb_copy_bits(from, 0, skb_put(to, hlen), hlen);
+		len -= hlen;
+	} else {
+		plen = min_t(int, skb_headlen(from), len);
+		if (plen) {
+			page = virt_to_head_page(from->head);
+			offset = from->data - (unsigned char *)page_address(page);
+			__skb_fill_page_desc(to, 0, page, offset, plen);
+			get_page(page);
+			j = 1;
+			len -= plen;
+		}
+	}
+
+	to->truesize += len + plen;
+	to->len += len + plen;
+	to->data_len += len + plen;
+
+	for (i = 0; i < skb_shinfo(from)->nr_frags; i++) {
+		if (!len)
+			break;
+		skb_shinfo(to)->frags[j] = skb_shinfo(from)->frags[i];
+		skb_shinfo(to)->frags[j].size = min_t(int, skb_shinfo(to)->frags[j].size, len);
+		len -= skb_shinfo(to)->frags[j].size;
+		skb_frag_ref(to, j);
+		j++;
+	}
+	skb_shinfo(to)->nr_frags = j;
+}
+EXPORT_SYMBOL_GPL(skb_zerocopy);
+
 void skb_copy_and_csum_dev(const struct sk_buff *skb, u8 *to)
 {
 	__wsum csum;
diff --git a/net/netfilter/nfnetlink_queue_core.c b/net/netfilter/nfnetlink_queue_core.c
index 21258cf..615ee12 100644
--- a/net/netfilter/nfnetlink_queue_core.c
+++ b/net/netfilter/nfnetlink_queue_core.c
@@ -235,51 +235,6 @@ nfqnl_flush(struct nfqnl_instance *queue, nfqnl_cmpfn cmpfn, unsigned long data)
 	spin_unlock_bh(&queue->lock);
 }
 
-static void
-nfqnl_zcopy(struct sk_buff *to, const struct sk_buff *from, int len, int hlen)
-{
-	int i, j = 0;
-	int plen = 0; /* length of skb->head fragment */
-	struct page *page;
-	unsigned int offset;
-
-	/* dont bother with small payloads */
-	if (len <= skb_tailroom(to)) {
-		skb_copy_bits(from, 0, skb_put(to, len), len);
-		return;
-	}
-
-	if (hlen) {
-		skb_copy_bits(from, 0, skb_put(to, hlen), hlen);
-		len -= hlen;
-	} else {
-		plen = min_t(int, skb_headlen(from), len);
-		if (plen) {
-			page = virt_to_head_page(from->head);
-			offset = from->data - (unsigned char *)page_address(page);
-			__skb_fill_page_desc(to, 0, page, offset, plen);
-			get_page(page);
-			j = 1;
-			len -= plen;
-		}
-	}
-
-	to->truesize += len + plen;
-	to->len += len + plen;
-	to->data_len += len + plen;
-
-	for (i = 0; i < skb_shinfo(from)->nr_frags; i++) {
-		if (!len)
-			break;
-		skb_shinfo(to)->frags[j] = skb_shinfo(from)->frags[i];
-		skb_shinfo(to)->frags[j].size = min_t(int, skb_shinfo(to)->frags[j].size, len);
-		len -= skb_shinfo(to)->frags[j].size;
-		skb_frag_ref(to, j);
-		j++;
-	}
-	skb_shinfo(to)->nr_frags = j;
-}
-
 static int
 nfqnl_put_packet_info(struct sk_buff *nlskb, struct sk_buff *packet,
 		      bool csum_verify)
@@ -304,7 +259,7 @@ nfqnl_build_packet_message(struct net *net, struct nfqnl_instance *queue,
 {
 	size_t size;
 	size_t data_len = 0, cap_len = 0;
-	int hlen = 0;
+	unsigned int hlen = 0;
 	struct sk_buff *skb;
 	struct nlattr *nla;
 	struct nfqnl_msg_packet_hdr *pmsg;
@@ -356,14 +311,8 @@ nfqnl_build_packet_message(struct net *net, struct nfqnl_instance *queue,
 		if (data_len > entskb->len)
 			data_len = entskb->len;
 
-		if (!entskb->head_frag ||
-		    skb_headlen(entskb) < L1_CACHE_BYTES ||
-		    skb_shinfo(entskb)->nr_frags >= MAX_SKB_FRAGS)
-			hlen = skb_headlen(entskb);
-
-		if (skb_has_frag_list(entskb))
-			hlen = entskb->len;
-		hlen = min_t(int, data_len, hlen);
+		hlen = skb_zerocopy_headlen(entskb);
+		hlen = min_t(unsigned int, hlen, data_len);
 		size += sizeof(struct nlattr) + hlen;
 		cap_len = entskb->len;
 		break;
@@ -504,7 +453,7 @@ nfqnl_build_packet_message(struct net *net, struct nfqnl_instance *queue,
 		nla->nla_type = NFQA_PAYLOAD;
 		nla->nla_len = nla_attr_size(data_len);
 
-		nfqnl_zcopy(skb, entskb, data_len, hlen);
+		skb_zerocopy(skb, entskb, data_len, hlen);
 	}
 
 	nlh->nlmsg_len = skb->len;
-- 
1.8.3.1

[PATCH net-next 2/6] openvswitch: Allow user space to announce ability to accept unaligned Netlink messages

[Thomas Graf]

Signed-off-by: Thomas Graf <tgraf@suug.ch>
Reviewed-by: Daniel Borkmann <dborkman@redhat.com>
---
 include/uapi/linux/openvswitch.h |  4 ++++
 net/openvswitch/datapath.c       | 14 ++++++++++++++
 net/openvswitch/datapath.h       |  2 ++
 3 files changed, 20 insertions(+)

diff --git a/include/uapi/linux/openvswitch.h b/include/uapi/linux/openvswitch.h
index d120f9f..07ef2c3 100644
--- a/include/uapi/linux/openvswitch.h
+++ b/include/uapi/linux/openvswitch.h
@@ -75,6 +75,7 @@ enum ovs_datapath_attr {
 	OVS_DP_ATTR_UPCALL_PID,		/* Netlink PID to receive upcalls */
 	OVS_DP_ATTR_STATS,		/* struct ovs_dp_stats */
 	OVS_DP_ATTR_MEGAFLOW_STATS,	/* struct ovs_dp_megaflow_stats */
+	OVS_DP_ATTR_USER_FEATURES,	/* OVS_DP_F_*  */
 	__OVS_DP_ATTR_MAX
 };
 
@@ -106,6 +107,9 @@ struct ovs_vport_stats {
 	__u64   tx_dropped;		/* no space available in linux  */
 };
 
+/* Allow last Netlink attribute to be unaligned */
+#define OVS_DP_F_UNALIGNED	(1 << 0)
+
 /* Fixed logical ports. */
 #define OVSP_LOCAL      ((__u32)0)
 
diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
index 0ac9cde..95d4424 100644
--- a/net/openvswitch/datapath.c
+++ b/net/openvswitch/datapath.c
@@ -1067,6 +1067,7 @@ static const struct genl_ops dp_flow_genl_ops[] = {
 static const struct nla_policy datapath_policy[OVS_DP_ATTR_MAX + 1] = {
 	[OVS_DP_ATTR_NAME] = { .type = NLA_NUL_STRING, .len = IFNAMSIZ - 1 },
 	[OVS_DP_ATTR_UPCALL_PID] = { .type = NLA_U32 },
+	[OVS_DP_ATTR_USER_FEATURES] = { .type = NLA_U32 },
 };
 
 static struct genl_family dp_datapath_genl_family = {
@@ -1125,6 +1126,9 @@ static int ovs_dp_cmd_fill_info(struct datapath *dp, struct sk_buff *skb,
 			&dp_megaflow_stats))
 		goto nla_put_failure;
 
+	if (nla_put_u32(skb, OVS_DP_ATTR_USER_FEATURES, dp->user_features))
+		goto nla_put_failure;
+
 	return genlmsg_end(skb, ovs_header);
 
 nla_put_failure:
@@ -1171,6 +1175,12 @@ static struct datapath *lookup_datapath(struct net *net,
 	return dp ? dp : ERR_PTR(-ENODEV);
 }
 
+static void ovs_dp_change(struct datapath *dp, struct nlattr **a)
+{
+	if (a[OVS_DP_ATTR_USER_FEATURES])
+		dp->user_features = nla_get_u32(a[OVS_DP_ATTR_USER_FEATURES]);
+}
+
 static int ovs_dp_cmd_new(struct sk_buff *skb, struct genl_info *info)
 {
 	struct nlattr **a = info->attrs;
@@ -1229,6 +1239,8 @@ static int ovs_dp_cmd_new(struct sk_buff *skb, struct genl_info *info)
 	parms.port_no = OVSP_LOCAL;
 	parms.upcall_portid = nla_get_u32(a[OVS_DP_ATTR_UPCALL_PID]);
 
+	ovs_dp_change(dp, a);
+
 	vport = new_vport(&parms);
 	if (IS_ERR(vport)) {
 		err = PTR_ERR(vport);
@@ -1332,6 +1344,8 @@ static int ovs_dp_cmd_set(struct sk_buff *skb, struct genl_info *info)
 	if (IS_ERR(dp))
 		goto unlock;
 
+	ovs_dp_change(dp, info->attrs);
+
 	reply = ovs_dp_cmd_build_info(dp, info, OVS_DP_CMD_NEW);
 	if (IS_ERR(reply)) {
 		err = PTR_ERR(reply);
diff --git a/net/openvswitch/datapath.h b/net/openvswitch/datapath.h
index 4067ea4..193e2e0 100644
--- a/net/openvswitch/datapath.h
+++ b/net/openvswitch/datapath.h
@@ -88,6 +88,8 @@ struct datapath {
 	/* Network namespace ref. */
 	struct net *net;
 #endif
+
+	u32 user_features;
 };
 
 /**
-- 
1.8.3.1

[PATCH net-next 3/6] openvswitch: Drop user features if old user space attempted to create datapath

[Thomas Graf]

Drop user features if an outdated user space instance that does not
understand the concept of user_features attempted to create a new
datapath.

Signed-off-by: Thomas Graf <tgraf@suug.ch>
---
 include/uapi/linux/openvswitch.h | 10 +++++++++-
 net/openvswitch/datapath.c       | 21 +++++++++++++++++++++
 2 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/include/uapi/linux/openvswitch.h b/include/uapi/linux/openvswitch.h
index 07ef2c3..970553c 100644
--- a/include/uapi/linux/openvswitch.h
+++ b/include/uapi/linux/openvswitch.h
@@ -40,7 +40,15 @@ struct ovs_header {
 
 #define OVS_DATAPATH_FAMILY  "ovs_datapath"
 #define OVS_DATAPATH_MCGROUP "ovs_datapath"
-#define OVS_DATAPATH_VERSION 0x1
+
+/* V2:
+ *   - API users are expected to provide OVS_DP_ATTR_USER_FEATURES
+ *     when creating the datapath.
+ */
+#define OVS_DATAPATH_VERSION 2
+
+/* First OVS datapath version to support features */
+#define OVS_DP_VER_FEATURES 2
 
 enum ovs_datapath_cmd {
 	OVS_DP_CMD_UNSPEC,
diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
index 95d4424..8eaa39a 100644
--- a/net/openvswitch/datapath.c
+++ b/net/openvswitch/datapath.c
@@ -1175,6 +1175,18 @@ static struct datapath *lookup_datapath(struct net *net,
 	return dp ? dp : ERR_PTR(-ENODEV);
 }
 
+static void ovs_dp_reset_user_features(struct sk_buff *skb, struct genl_info *info)
+{
+	struct datapath *dp;
+
+	dp = lookup_datapath(sock_net(skb->sk), info->userhdr, info->attrs);
+	if (!dp)
+		return;
+
+	WARN(dp->user_features, "Dropping previously announced user features\n");
+	dp->user_features = 0;
+}
+
 static void ovs_dp_change(struct datapath *dp, struct nlattr **a)
 {
 	if (a[OVS_DP_ATTR_USER_FEATURES])
@@ -1247,6 +1259,15 @@ static int ovs_dp_cmd_new(struct sk_buff *skb, struct genl_info *info)
 		if (err == -EBUSY)
 			err = -EEXIST;
 
+		if (err == -EEXIST) {
+			/* An outdated user space instance that does not understand
+			 * the concept of user_features has attempted to create a new
+			 * datapath and is likely to reuse it. Drop all user features.
+			 */
+			if (info->genlhdr->version < OVS_DP_VER_FEATURES)
+				ovs_dp_reset_user_features(skb, info);
+		}
+
 		goto err_destroy_ports_array;
 	}
 
-- 
1.8.3.1

[PATCH net-next 4/6] openvswitch: Pass datapath into userspace queue functions

[Thomas Graf]

Allows removing the net and dp_ifindex argument and simplify the
code.

Signed-off-by: Thomas Graf <tgraf@suug.ch>
---
 net/openvswitch/datapath.c | 34 ++++++++++++++--------------------
 1 file changed, 14 insertions(+), 20 deletions(-)

diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
index 8eaa39a..8f6318c 100644
--- a/net/openvswitch/datapath.c
+++ b/net/openvswitch/datapath.c
@@ -108,10 +108,9 @@ int lockdep_ovsl_is_held(void)
 #endif
 
 static struct vport *new_vport(const struct vport_parms *);
-static int queue_gso_packets(struct net *, int dp_ifindex, struct sk_buff *,
+static int queue_gso_packets(struct datapath *dp, struct sk_buff *,
 			     const struct dp_upcall_info *);
-static int queue_userspace_packet(struct net *, int dp_ifindex,
-				  struct sk_buff *,
+static int queue_userspace_packet(struct datapath *dp, struct sk_buff *,
 				  const struct dp_upcall_info *);
 
 /* Must be called with rcu_read_lock or ovs_mutex. */
@@ -277,7 +276,6 @@ int ovs_dp_upcall(struct datapath *dp, struct sk_buff *skb,
 		  const struct dp_upcall_info *upcall_info)
 {
 	struct dp_stats_percpu *stats;
-	int dp_ifindex;
 	int err;
 
 	if (upcall_info->portid == 0) {
@@ -285,16 +283,10 @@ int ovs_dp_upcall(struct datapath *dp, struct sk_buff *skb,
 		goto err;
 	}
 
-	dp_ifindex = get_dpifindex(dp);
-	if (!dp_ifindex) {
-		err = -ENODEV;
-		goto err;
-	}
-
 	if (!skb_is_gso(skb))
-		err = queue_userspace_packet(ovs_dp_get_net(dp), dp_ifindex, skb, upcall_info);
+		err = queue_userspace_packet(dp, skb, upcall_info);
 	else
-		err = queue_gso_packets(ovs_dp_get_net(dp), dp_ifindex, skb, upcall_info);
+		err = queue_gso_packets(dp, skb, upcall_info);
 	if (err)
 		goto err;
 
@@ -310,8 +302,7 @@ err:
 	return err;
 }
 
-static int queue_gso_packets(struct net *net, int dp_ifindex,
-			     struct sk_buff *skb,
+static int queue_gso_packets(struct datapath *dp, struct sk_buff *skb,
 			     const struct dp_upcall_info *upcall_info)
 {
 	unsigned short gso_type = skb_shinfo(skb)->gso_type;
@@ -327,7 +318,7 @@ static int queue_gso_packets(struct net *net, int dp_ifindex,
 	/* Queue all of the segments. */
 	skb = segs;
 	do {
-		err = queue_userspace_packet(net, dp_ifindex, skb, upcall_info);
+		err = queue_userspace_packet(dp, skb, upcall_info);
 		if (err)
 			break;
 
@@ -394,8 +385,7 @@ static size_t upcall_msg_size(const struct sk_buff *skb,
 	return size;
 }
 
-static int queue_userspace_packet(struct net *net, int dp_ifindex,
-				  struct sk_buff *skb,
+static int queue_userspace_packet(struct datapath *dp, struct sk_buff *skb,
 				  const struct dp_upcall_info *upcall_info)
 {
 	struct ovs_header *upcall;
@@ -403,11 +393,15 @@ static int queue_userspace_packet(struct net *net, int dp_ifindex,
 	struct sk_buff *user_skb; /* to be queued to userspace */
 	struct nlattr *nla;
 	struct genl_info info = {
-		.dst_sk = net->genl_sock,
+		.dst_sk = ovs_dp_get_net(dp)->genl_sock,
 		.snd_portid = upcall_info->portid,
 	};
 	size_t len;
-	int err;
+	int err, dp_ifindex;
+
+	dp_ifindex = get_dpifindex(dp);
+	if (!dp_ifindex)
+		return -ENODEV;
 
 	if (vlan_tx_tag_present(skb)) {
 		nskb = skb_clone(skb, GFP_ATOMIC);
@@ -452,7 +446,7 @@ static int queue_userspace_packet(struct net *net, int dp_ifindex,
 	skb_copy_and_csum_dev(skb, nla_data(nla));
 
 	genlmsg_end(user_skb, upcall);
-	err = genlmsg_unicast(net, user_skb, upcall_info->portid);
+	err = genlmsg_unicast(ovs_dp_get_net(dp), user_skb, upcall_info->portid);
 
 out:
 	kfree_skb(nskb);
-- 
1.8.3.1

[PATCH net-next 5/6] openvswitch: Use skb_zerocopy() for upcall

[Thomas Graf]

Use of skb_zerocopy() can avoid the expensive call to memcpy()
when copying the packet data into the Netlink skb. Completes
checksum through skb_checksum_help() if not already done in
GSO segmentation.

Zerocopy is only performed if user space supported unaligned
Netlink messages. memory mapped netlink i/o is preferred over
zerocopy if it is set up.

Cost of upcall is significantly reduced from:
+   7.48%       vhost-8471  [k] memcpy
+   5.57%     ovs-vswitchd  [k] memcpy
+   2.81%       vhost-8471  [k] csum_partial_copy_generic

to:
+   5.72%     ovs-vswitchd  [k] memcpy
+   3.32%       vhost-5153  [k] memcpy
+   0.68%       vhost-5153  [k] skb_zerocopy

(megaflows disabled)

Signed-off-by: Thomas Graf <tgraf@suug.ch>
---
 net/openvswitch/datapath.c | 37 +++++++++++++++++++++++++++++--------
 1 file changed, 29 insertions(+), 8 deletions(-)

diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
index 8f6318c..ffed1cd 100644
--- a/net/openvswitch/datapath.c
+++ b/net/openvswitch/datapath.c
@@ -371,11 +371,11 @@ static size_t key_attr_size(void)
 		+ nla_total_size(28); /* OVS_KEY_ATTR_ND */
 }
 
-static size_t upcall_msg_size(const struct sk_buff *skb,
-			      const struct nlattr *userdata)
+static size_t upcall_msg_size(const struct nlattr *userdata,
+			      unsigned int hdrlen)
 {
 	size_t size = NLMSG_ALIGN(sizeof(struct ovs_header))
-		+ nla_total_size(skb->len) /* OVS_PACKET_ATTR_PACKET */
+		+ nla_total_size(hdrlen) /* OVS_PACKET_ATTR_PACKET */
 		+ nla_total_size(key_attr_size()); /* OVS_PACKET_ATTR_KEY */
 
 	/* OVS_PACKET_ATTR_USERDATA */
@@ -397,6 +397,7 @@ static int queue_userspace_packet(struct datapath *dp, struct sk_buff *skb,
 		.snd_portid = upcall_info->portid,
 	};
 	size_t len;
+	unsigned int hlen;
 	int err, dp_ifindex;
 
 	dp_ifindex = get_dpifindex(dp);
@@ -421,7 +422,21 @@ static int queue_userspace_packet(struct datapath *dp, struct sk_buff *skb,
 		goto out;
 	}
 
-	len = upcall_msg_size(skb, upcall_info->userdata);
+	/* Complete checksum if needed */
+	if (skb->ip_summed == CHECKSUM_PARTIAL &&
+	    (err = skb_checksum_help(skb)))
+		goto out;
+
+	/* Older versions of OVS user space enforce alignment of the last
+	 * Netlink attribute to NLA_ALIGNTO which would require extensive
+	 * padding logic. Only perform zerocopy if padding is not required.
+	 */
+	if (dp->user_features & OVS_DP_F_UNALIGNED)
+		hlen = skb_zerocopy_headlen(skb);
+	else
+		hlen = skb->len;
+
+	len = upcall_msg_size(upcall_info->userdata, hlen);
 	user_skb = genlmsg_new_unicast(len, &info, GFP_ATOMIC);
 	if (!user_skb) {
 		err = -ENOMEM;
@@ -441,13 +456,19 @@ static int queue_userspace_packet(struct datapath *dp, struct sk_buff *skb,
 			  nla_len(upcall_info->userdata),
 			  nla_data(upcall_info->userdata));
 
-	nla = __nla_reserve(user_skb, OVS_PACKET_ATTR_PACKET, skb->len);
+	/* Only reserve room for attribute header, packet data is added
+	 * in skb_zerocopy() */
+	if (!(nla = nla_reserve(user_skb, OVS_PACKET_ATTR_PACKET, 0))) {
+		err = -ENOBUFS;
+		goto out;
+	}
+	nla->nla_len = nla_attr_size(skb->len);
 
-	skb_copy_and_csum_dev(skb, nla_data(nla));
+	skb_zerocopy(user_skb, skb, skb->len, hlen);
 
-	genlmsg_end(user_skb, upcall);
-	err = genlmsg_unicast(ovs_dp_get_net(dp), user_skb, upcall_info->portid);
+	((struct nlmsghdr *) user_skb->data)->nlmsg_len = user_skb->len;
 
+	err = genlmsg_unicast(ovs_dp_get_net(dp), user_skb, upcall_info->portid);
 out:
 	kfree_skb(nskb);
 	return err;
-- 
1.8.3.1

[PATCH net-next 6/6] openvswitch: Compute checksum in skb_gso_segment() if needed

[Thomas Graf]

The copy & csum optimization is no longer present with zerocopy
enabled. Compute the checksum in skb_gso_segment() directly by
dropping the HW CSUM capability from the features passed in.

Signed-off-by: Thomas Graf <tgraf@suug.ch>
---
 net/openvswitch/datapath.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
index ffed1cd..20ac30e 100644
--- a/net/openvswitch/datapath.c
+++ b/net/openvswitch/datapath.c
@@ -311,7 +311,7 @@ static int queue_gso_packets(struct datapath *dp, struct sk_buff *skb,
 	struct sk_buff *segs, *nskb;
 	int err;
 
-	segs = __skb_gso_segment(skb, NETIF_F_SG | NETIF_F_HW_CSUM, false);
+	segs = __skb_gso_segment(skb, NETIF_F_SG, false);
 	if (IS_ERR(segs))
 		return PTR_ERR(segs);
 
-- 
1.8.3.1

Re: [PATCH net-next 0/6 v9] Open vSwitch zercopy upcall optimiziation

[Jesse Gross]

On Fri, Dec 13, 2013 at 6:22 AM, Thomas Graf <tgraf@suug.ch> wrote:
> Series implementing a zerocopy method for OVS upcall messages. Based
> on top of commit: (''openvswitch: Enable memory mapped Netlink i/o'')

Series applied, thanks.