[PATCH bpf-next v6 0/2] Optimize bpf_redirect_map()/xdp_do_redirect()

[PATCH bpf-next v6 0/2] Optimize bpf_redirect_map()/xdp_do_redirect()

[Björn Töpel]

Hi XDP-folks,

This two patch series contain two optimizations for the
bpf_redirect_map() helper and the xdp_do_redirect() function.

The bpf_redirect_map() optimization is about avoiding the map lookup
dispatching. Instead of having a switch-statement and selecting the
correct lookup function, we let bpf_redirect_map() be a map operation,
where each map has its own bpf_redirect_map() implementation. This way
the run-time lookup is avoided.

The xdp_do_redirect() patch restructures the code, so that the map
pointer indirection can be avoided.

Performance-wise I got 4% improvement for XSKMAP
(sample:xdpsock/rx-drop), and 8% (sample:xdp_redirect_map) on my
machine.

@Jesper/@Toke I kept your Acked-by: for patch 2. Let me know, if you
don't agree with that decision.

More details in each commit.

Changelog:
v5->v6:  Removed REDIR enum, and instead use map_id and map_type. (Daniel)
         Applied Daniel's fixups on patch 1. (Daniel)
v4->v5:  Renamed map operation to map_redirect. (Daniel)
v3->v4:  Made bpf_redirect_map() a map operation. (Daniel)
v2->v3:  Fix build when CONFIG_NET is not set. (lkp)
v1->v2:  Removed warning when CONFIG_BPF_SYSCALL was not set. (lkp)
         Cleaned up case-clause in xdp_do_generic_redirect_map(). (Toke)
         Re-added comment. (Toke)
rfc->v1: Use map_id, and remove bpf_clear_redirect_map(). (Toke)
         Get rid of the macro and use __always_inline. (Jesper)

rfc: https://lore.kernel.org/bpf/87im7fy9nc.fsf@toke.dk/ (Cover not on lore!)
v1:  https://lore.kernel.org/bpf/20210219145922.63655-1-bjorn.topel@gmail.com/
v2:  https://lore.kernel.org/bpf/20210220153056.111968-1-bjorn.topel@gmail.com/
v3:  https://lore.kernel.org/bpf/20210221200954.164125-3-bjorn.topel@gmail.com/
v4:  https://lore.kernel.org/bpf/20210226112322.144927-1-bjorn.topel@gmail.com/
v5:  https://lore.kernel.org/bpf/20210227122139.183284-1-bjorn.topel@gmail.com/

Björn Töpel (2):
  bpf, xdp: make bpf_redirect_map() a map operation
  bpf, xdp: restructure redirect actions

 include/linux/bpf.h        |  26 ++---
 include/linux/filter.h     |  31 +++++-
 include/net/xdp_sock.h     |  19 ----
 include/trace/events/xdp.h |  62 ++++++-----
 kernel/bpf/cpumap.c        |   9 +-
 kernel/bpf/devmap.c        |  17 ++-
 kernel/bpf/verifier.c      |  13 ++-
 net/core/filter.c          | 209 ++++++++++++++-----------------------
 net/xdp/xskmap.c           |  17 ++-
 9 files changed, 195 insertions(+), 208 deletions(-)


base-commit: 5e6d87315279db3abe69e2ebfd05fa8f5c014295
-- 
2.27.0

[PATCH bpf-next v6 1/2] bpf, xdp: make bpf_redirect_map() a map operation

[Björn Töpel]

From: Björn Töpel <bjorn.topel@intel.com>

Currently the bpf_redirect_map() implementation dispatches to the
correct map-lookup function via a switch-statement. To avoid the
dispatching, this change adds bpf_redirect_map() as a map
operation. Each map provides its bpf_redirect_map() version, and
correct function is automatically selected by the BPF verifier.

A nice side-effect of the code movement is that the map lookup
functions are now local to the map implementation files, which removes
one additional function call.

Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Acked-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Björn Töpel <bjorn.topel@intel.com>
---
 include/linux/bpf.h    | 26 ++++++--------------------
 include/linux/filter.h | 27 +++++++++++++++++++++++++++
 include/net/xdp_sock.h | 19 -------------------
 kernel/bpf/cpumap.c    |  8 +++++++-
 kernel/bpf/devmap.c    | 16 ++++++++++++++--
 kernel/bpf/verifier.c  | 13 +++++++++++--
 net/core/filter.c      | 39 +--------------------------------------
 net/xdp/xskmap.c       | 16 ++++++++++++++++
 8 files changed, 82 insertions(+), 82 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index c931bc97019d..a25730eaa148 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -118,6 +118,9 @@ struct bpf_map_ops {
 					   void *owner, u32 size);
 	struct bpf_local_storage __rcu ** (*map_owner_storage_ptr)(void *owner);
 
+	/* Misc helpers.*/
+	int (*map_redirect)(struct bpf_map *map, u32 ifindex, u64 flags);
+
 	/* map_meta_equal must be implemented for maps that can be
 	 * used as an inner map.  It is a runtime check to ensure
 	 * an inner map can be inserted to an outer map.
@@ -1450,9 +1453,9 @@ struct btf *bpf_get_btf_vmlinux(void);
 /* Map specifics */
 struct xdp_buff;
 struct sk_buff;
+struct bpf_dtab_netdev;
+struct bpf_cpu_map_entry;
 
-struct bpf_dtab_netdev *__dev_map_lookup_elem(struct bpf_map *map, u32 key);
-struct bpf_dtab_netdev *__dev_map_hash_lookup_elem(struct bpf_map *map, u32 key);
 void __dev_flush(void);
 int dev_xdp_enqueue(struct net_device *dev, struct xdp_buff *xdp,
 		    struct net_device *dev_rx);
@@ -1462,7 +1465,6 @@ int dev_map_generic_redirect(struct bpf_dtab_netdev *dst, struct sk_buff *skb,
 			     struct bpf_prog *xdp_prog);
 bool dev_map_can_have_prog(struct bpf_map *map);
 
-struct bpf_cpu_map_entry *__cpu_map_lookup_elem(struct bpf_map *map, u32 key);
 void __cpu_map_flush(void);
 int cpu_map_enqueue(struct bpf_cpu_map_entry *rcpu, struct xdp_buff *xdp,
 		    struct net_device *dev_rx);
@@ -1593,17 +1595,6 @@ static inline int bpf_obj_get_user(const char __user *pathname, int flags)
 	return -EOPNOTSUPP;
 }
 
-static inline struct net_device  *__dev_map_lookup_elem(struct bpf_map *map,
-						       u32 key)
-{
-	return NULL;
-}
-
-static inline struct net_device  *__dev_map_hash_lookup_elem(struct bpf_map *map,
-							     u32 key)
-{
-	return NULL;
-}
 static inline bool dev_map_can_have_prog(struct bpf_map *map)
 {
 	return false;
@@ -1615,6 +1606,7 @@ static inline void __dev_flush(void)
 
 struct xdp_buff;
 struct bpf_dtab_netdev;
+struct bpf_cpu_map_entry;
 
 static inline
 int dev_xdp_enqueue(struct net_device *dev, struct xdp_buff *xdp,
@@ -1639,12 +1631,6 @@ static inline int dev_map_generic_redirect(struct bpf_dtab_netdev *dst,
 	return 0;
 }
 
-static inline
-struct bpf_cpu_map_entry *__cpu_map_lookup_elem(struct bpf_map *map, u32 key)
-{
-	return NULL;
-}
-
 static inline void __cpu_map_flush(void)
 {
 }
diff --git a/include/linux/filter.h b/include/linux/filter.h
index 3b00fc906ccd..008691fd3b58 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -1472,4 +1472,31 @@ static inline bool bpf_sk_lookup_run_v6(struct net *net, int protocol,
 }
 #endif /* IS_ENABLED(CONFIG_IPV6) */
 
+static __always_inline int __bpf_xdp_redirect_map(struct bpf_map *map, u32 ifindex, u64 flags,
+						  void *lookup_elem(struct bpf_map *map, u32 key))
+{
+	struct bpf_redirect_info *ri = this_cpu_ptr(&bpf_redirect_info);
+
+	/* Lower bits of the flags are used as return code on lookup failure */
+	if (unlikely(flags > XDP_TX))
+		return XDP_ABORTED;
+
+	ri->tgt_value = lookup_elem(map, ifindex);
+	if (unlikely(!ri->tgt_value)) {
+		/* If the lookup fails we want to clear out the state in the
+		 * redirect_info struct completely, so that if an eBPF program
+		 * performs multiple lookups, the last one always takes
+		 * precedence.
+		 */
+		WRITE_ONCE(ri->map, NULL);
+		return flags;
+	}
+
+	ri->flags = flags;
+	ri->tgt_index = ifindex;
+	WRITE_ONCE(ri->map, map);
+
+	return XDP_REDIRECT;
+}
+
 #endif /* __LINUX_FILTER_H__ */
diff --git a/include/net/xdp_sock.h b/include/net/xdp_sock.h
index cc17bc957548..9c0722c6d7ac 100644
--- a/include/net/xdp_sock.h
+++ b/include/net/xdp_sock.h
@@ -80,19 +80,6 @@ int xsk_generic_rcv(struct xdp_sock *xs, struct xdp_buff *xdp);
 int __xsk_map_redirect(struct xdp_sock *xs, struct xdp_buff *xdp);
 void __xsk_map_flush(void);
 
-static inline struct xdp_sock *__xsk_map_lookup_elem(struct bpf_map *map,
-						     u32 key)
-{
-	struct xsk_map *m = container_of(map, struct xsk_map, map);
-	struct xdp_sock *xs;
-
-	if (key >= map->max_entries)
-		return NULL;
-
-	xs = READ_ONCE(m->xsk_map[key]);
-	return xs;
-}
-
 #else
 
 static inline int xsk_generic_rcv(struct xdp_sock *xs, struct xdp_buff *xdp)
@@ -109,12 +96,6 @@ static inline void __xsk_map_flush(void)
 {
 }
 
-static inline struct xdp_sock *__xsk_map_lookup_elem(struct bpf_map *map,
-						     u32 key)
-{
-	return NULL;
-}
-
 #endif /* CONFIG_XDP_SOCKETS */
 
 #endif /* _LINUX_XDP_SOCK_H */
diff --git a/kernel/bpf/cpumap.c b/kernel/bpf/cpumap.c
index 5d1469de6921..7352d4160b7f 100644
--- a/kernel/bpf/cpumap.c
+++ b/kernel/bpf/cpumap.c
@@ -563,7 +563,7 @@ static void cpu_map_free(struct bpf_map *map)
 	kfree(cmap);
 }
 
-struct bpf_cpu_map_entry *__cpu_map_lookup_elem(struct bpf_map *map, u32 key)
+static void *__cpu_map_lookup_elem(struct bpf_map *map, u32 key)
 {
 	struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
 	struct bpf_cpu_map_entry *rcpu;
@@ -600,6 +600,11 @@ static int cpu_map_get_next_key(struct bpf_map *map, void *key, void *next_key)
 	return 0;
 }
 
+static int cpu_map_redirect(struct bpf_map *map, u32 ifindex, u64 flags)
+{
+	return __bpf_xdp_redirect_map(map, ifindex, flags, __cpu_map_lookup_elem);
+}
+
 static int cpu_map_btf_id;
 const struct bpf_map_ops cpu_map_ops = {
 	.map_meta_equal		= bpf_map_meta_equal,
@@ -612,6 +617,7 @@ const struct bpf_map_ops cpu_map_ops = {
 	.map_check_btf		= map_check_no_btf,
 	.map_btf_name		= "bpf_cpu_map",
 	.map_btf_id		= &cpu_map_btf_id,
+	.map_redirect		= cpu_map_redirect,
 };
 
 static void bq_flush_to_queue(struct xdp_bulk_queue *bq)
diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
index 85d9d1b72a33..f7f42448259f 100644
--- a/kernel/bpf/devmap.c
+++ b/kernel/bpf/devmap.c
@@ -258,7 +258,7 @@ static int dev_map_get_next_key(struct bpf_map *map, void *key, void *next_key)
 	return 0;
 }
 
-struct bpf_dtab_netdev *__dev_map_hash_lookup_elem(struct bpf_map *map, u32 key)
+static void *__dev_map_hash_lookup_elem(struct bpf_map *map, u32 key)
 {
 	struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
 	struct hlist_head *head = dev_map_index_hash(dtab, key);
@@ -392,7 +392,7 @@ void __dev_flush(void)
  * update happens in parallel here a dev_put wont happen until after reading the
  * ifindex.
  */
-struct bpf_dtab_netdev *__dev_map_lookup_elem(struct bpf_map *map, u32 key)
+static void *__dev_map_lookup_elem(struct bpf_map *map, u32 key)
 {
 	struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
 	struct bpf_dtab_netdev *obj;
@@ -735,6 +735,16 @@ static int dev_map_hash_update_elem(struct bpf_map *map, void *key, void *value,
 					 map, key, value, map_flags);
 }
 
+static int dev_map_redirect(struct bpf_map *map, u32 ifindex, u64 flags)
+{
+	return __bpf_xdp_redirect_map(map, ifindex, flags, __dev_map_lookup_elem);
+}
+
+static int dev_hash_map_redirect(struct bpf_map *map, u32 ifindex, u64 flags)
+{
+	return __bpf_xdp_redirect_map(map, ifindex, flags, __dev_map_hash_lookup_elem);
+}
+
 static int dev_map_btf_id;
 const struct bpf_map_ops dev_map_ops = {
 	.map_meta_equal = bpf_map_meta_equal,
@@ -747,6 +757,7 @@ const struct bpf_map_ops dev_map_ops = {
 	.map_check_btf = map_check_no_btf,
 	.map_btf_name = "bpf_dtab",
 	.map_btf_id = &dev_map_btf_id,
+	.map_redirect = dev_map_redirect,
 };
 
 static int dev_map_hash_map_btf_id;
@@ -761,6 +772,7 @@ const struct bpf_map_ops dev_map_hash_ops = {
 	.map_check_btf = map_check_no_btf,
 	.map_btf_name = "bpf_dtab",
 	.map_btf_id = &dev_map_hash_map_btf_id,
+	.map_redirect = dev_hash_map_redirect,
 };
 
 static void dev_map_hash_remove_netdev(struct bpf_dtab *dtab,
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 9fe90ce52a65..97eb0b2435b8 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -5582,7 +5582,8 @@ record_func_map(struct bpf_verifier_env *env, struct bpf_call_arg_meta *meta,
 	    func_id != BPF_FUNC_map_push_elem &&
 	    func_id != BPF_FUNC_map_pop_elem &&
 	    func_id != BPF_FUNC_map_peek_elem &&
-	    func_id != BPF_FUNC_for_each_map_elem)
+	    func_id != BPF_FUNC_for_each_map_elem &&
+	    func_id != BPF_FUNC_redirect_map)
 		return 0;
 
 	if (map == NULL) {
@@ -12017,7 +12018,8 @@ static int do_misc_fixups(struct bpf_verifier_env *env)
 		     insn->imm == BPF_FUNC_map_delete_elem ||
 		     insn->imm == BPF_FUNC_map_push_elem   ||
 		     insn->imm == BPF_FUNC_map_pop_elem    ||
-		     insn->imm == BPF_FUNC_map_peek_elem)) {
+		     insn->imm == BPF_FUNC_map_peek_elem   ||
+		     insn->imm == BPF_FUNC_redirect_map)) {
 			aux = &env->insn_aux_data[i + delta];
 			if (bpf_map_ptr_poisoned(aux))
 				goto patch_call_imm;
@@ -12059,6 +12061,9 @@ static int do_misc_fixups(struct bpf_verifier_env *env)
 				     (int (*)(struct bpf_map *map, void *value))NULL));
 			BUILD_BUG_ON(!__same_type(ops->map_peek_elem,
 				     (int (*)(struct bpf_map *map, void *value))NULL));
+			BUILD_BUG_ON(!__same_type(ops->map_redirect,
+				     (int (*)(struct bpf_map *map, u32 ifindex, u64 flags))NULL));
+
 patch_map_ops_generic:
 			switch (insn->imm) {
 			case BPF_FUNC_map_lookup_elem:
@@ -12085,6 +12090,10 @@ static int do_misc_fixups(struct bpf_verifier_env *env)
 				insn->imm = BPF_CAST_CALL(ops->map_peek_elem) -
 					    __bpf_call_base;
 				continue;
+			case BPF_FUNC_redirect_map:
+				insn->imm = BPF_CAST_CALL(ops->map_redirect) -
+					    __bpf_call_base;
+				continue;
 			}
 
 			goto patch_call_imm;
diff --git a/net/core/filter.c b/net/core/filter.c
index 588b19ba0da8..183b0aa6b027 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -3943,22 +3943,6 @@ void xdp_do_flush(void)
 }
 EXPORT_SYMBOL_GPL(xdp_do_flush);
 
-static inline void *__xdp_map_lookup_elem(struct bpf_map *map, u32 index)
-{
-	switch (map->map_type) {
-	case BPF_MAP_TYPE_DEVMAP:
-		return __dev_map_lookup_elem(map, index);
-	case BPF_MAP_TYPE_DEVMAP_HASH:
-		return __dev_map_hash_lookup_elem(map, index);
-	case BPF_MAP_TYPE_CPUMAP:
-		return __cpu_map_lookup_elem(map, index);
-	case BPF_MAP_TYPE_XSKMAP:
-		return __xsk_map_lookup_elem(map, index);
-	default:
-		return NULL;
-	}
-}
-
 void bpf_clear_redirect_map(struct bpf_map *map)
 {
 	struct bpf_redirect_info *ri;
@@ -4112,28 +4096,7 @@ static const struct bpf_func_proto bpf_xdp_redirect_proto = {
 BPF_CALL_3(bpf_xdp_redirect_map, struct bpf_map *, map, u32, ifindex,
 	   u64, flags)
 {
-	struct bpf_redirect_info *ri = this_cpu_ptr(&bpf_redirect_info);
-
-	/* Lower bits of the flags are used as return code on lookup failure */
-	if (unlikely(flags > XDP_TX))
-		return XDP_ABORTED;
-
-	ri->tgt_value = __xdp_map_lookup_elem(map, ifindex);
-	if (unlikely(!ri->tgt_value)) {
-		/* If the lookup fails we want to clear out the state in the
-		 * redirect_info struct completely, so that if an eBPF program
-		 * performs multiple lookups, the last one always takes
-		 * precedence.
-		 */
-		WRITE_ONCE(ri->map, NULL);
-		return flags;
-	}
-
-	ri->flags = flags;
-	ri->tgt_index = ifindex;
-	WRITE_ONCE(ri->map, map);
-
-	return XDP_REDIRECT;
+	return map->ops->map_redirect(map, ifindex, flags);
 }
 
 static const struct bpf_func_proto bpf_xdp_redirect_map_proto = {
diff --git a/net/xdp/xskmap.c b/net/xdp/xskmap.c
index 113fd9017203..fbeb4870f798 100644
--- a/net/xdp/xskmap.c
+++ b/net/xdp/xskmap.c
@@ -125,6 +125,16 @@ static int xsk_map_gen_lookup(struct bpf_map *map, struct bpf_insn *insn_buf)
 	return insn - insn_buf;
 }
 
+static void *__xsk_map_lookup_elem(struct bpf_map *map, u32 key)
+{
+	struct xsk_map *m = container_of(map, struct xsk_map, map);
+
+	if (key >= map->max_entries)
+		return NULL;
+
+	return READ_ONCE(m->xsk_map[key]);
+}
+
 static void *xsk_map_lookup_elem(struct bpf_map *map, void *key)
 {
 	WARN_ON_ONCE(!rcu_read_lock_held());
@@ -215,6 +225,11 @@ static int xsk_map_delete_elem(struct bpf_map *map, void *key)
 	return 0;
 }
 
+static int xsk_map_redirect(struct bpf_map *map, u32 ifindex, u64 flags)
+{
+	return __bpf_xdp_redirect_map(map, ifindex, flags, __xsk_map_lookup_elem);
+}
+
 void xsk_map_try_sock_delete(struct xsk_map *map, struct xdp_sock *xs,
 			     struct xdp_sock **map_entry)
 {
@@ -247,4 +262,5 @@ const struct bpf_map_ops xsk_map_ops = {
 	.map_check_btf = map_check_no_btf,
 	.map_btf_name = "xsk_map",
 	.map_btf_id = &xsk_map_btf_id,
+	.map_redirect = xsk_map_redirect,
 };
-- 
2.27.0

[PATCH bpf-next v6 2/2] bpf, xdp: restructure redirect actions

[Björn Töpel]

From: Björn Töpel <bjorn.topel@intel.com>

The XDP_REDIRECT implementations for maps and non-maps are fairly
similar, but obviously need to take different code paths depending on
if the target is using a map or not. Today, the redirect targets for
XDP either uses a map, or is based on ifindex.

Here, the map type and id are added to bpf_redirect_info, instead of
the actual map. Map type, map item/ifindex, and the map_id (if any) is
passed to xdp_do_redirect().

For ifindex-based redirect, used by the bpf_redirect() XDP BFP helper,
a special map type/id are used. Map type of UNSPEC together with map id
equal to INT_MAX has the special meaning of an ifindex based
redirect. Note that valid map ids are 1 inclusive, INT_MAX exclusive
([1,INT_MAX[).

In addition to making the code easier to follow, using explicit type
and id in bpf_redirect_info has a slight positive performance impact
by avoiding a pointer indirection for the map type lookup, and instead
use the cacheline for bpf_redirect_info.

Since the actual map is not passed via bpf_redirect_info anymore, the
map lookup is only done in the BPF helper. This means that the
bpf_clear_redirect_map() function can be removed. The actual map item
is RCU protected.

The bpf_redirect_info flags member is not used by XDP, and not
read/written any more. The map member is only written to when
required/used, and not unconditionally.

Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Acked-by: Toke Høiland-Jørgensen <toke@redhat.com>
Reviewed-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Signed-off-by: Björn Töpel <bjorn.topel@intel.com>
---
 include/linux/filter.h     |  10 ++-
 include/trace/events/xdp.h |  62 ++++++++------
 kernel/bpf/cpumap.c        |   1 -
 kernel/bpf/devmap.c        |   1 -
 net/core/filter.c          | 170 ++++++++++++++++---------------------
 net/xdp/xskmap.c           |   1 -
 6 files changed, 116 insertions(+), 129 deletions(-)

diff --git a/include/linux/filter.h b/include/linux/filter.h
index 008691fd3b58..b2b85b2cad8e 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -646,7 +646,8 @@ struct bpf_redirect_info {
 	u32 flags;
 	u32 tgt_index;
 	void *tgt_value;
-	struct bpf_map *map;
+	u32 map_id;
+	enum bpf_map_type map_type;
 	u32 kern_flags;
 	struct bpf_nh_params nh;
 };
@@ -1488,13 +1489,14 @@ static __always_inline int __bpf_xdp_redirect_map(struct bpf_map *map, u32 ifind
 		 * performs multiple lookups, the last one always takes
 		 * precedence.
 		 */
-		WRITE_ONCE(ri->map, NULL);
+		ri->map_id = INT_MAX; /* Valid map id idr range: [1,INT_MAX[ */
+		ri->map_type = BPF_MAP_TYPE_UNSPEC;
 		return flags;
 	}
 
-	ri->flags = flags;
 	ri->tgt_index = ifindex;
-	WRITE_ONCE(ri->map, map);
+	ri->map_id = map->id;
+	ri->map_type = map->map_type;
 
 	return XDP_REDIRECT;
 }
diff --git a/include/trace/events/xdp.h b/include/trace/events/xdp.h
index 76a97176ab81..fcad3645a70b 100644
--- a/include/trace/events/xdp.h
+++ b/include/trace/events/xdp.h
@@ -86,19 +86,15 @@ struct _bpf_dtab_netdev {
 };
 #endif /* __DEVMAP_OBJ_TYPE */
 
-#define devmap_ifindex(tgt, map)				\
-	(((map->map_type == BPF_MAP_TYPE_DEVMAP ||	\
-		  map->map_type == BPF_MAP_TYPE_DEVMAP_HASH)) ? \
-	  ((struct _bpf_dtab_netdev *)tgt)->dev->ifindex : 0)
-
 DECLARE_EVENT_CLASS(xdp_redirect_template,
 
 	TP_PROTO(const struct net_device *dev,
 		 const struct bpf_prog *xdp,
 		 const void *tgt, int err,
-		 const struct bpf_map *map, u32 index),
+		 enum bpf_map_type map_type,
+		 u32 map_id, u32 index),
 
-	TP_ARGS(dev, xdp, tgt, err, map, index),
+	TP_ARGS(dev, xdp, tgt, err, map_type, map_id, index),
 
 	TP_STRUCT__entry(
 		__field(int, prog_id)
@@ -111,14 +107,22 @@ DECLARE_EVENT_CLASS(xdp_redirect_template,
 	),
 
 	TP_fast_assign(
+		u32 ifindex = 0, map_index = index;
+
+		if (map_type == BPF_MAP_TYPE_DEVMAP || map_type == BPF_MAP_TYPE_DEVMAP_HASH) {
+			ifindex = ((struct _bpf_dtab_netdev *)tgt)->dev->ifindex;
+		} else if (map_type == BPF_MAP_TYPE_UNSPEC && map_id == INT_MAX) {
+			ifindex = index;
+			map_index = 0;
+		}
+
 		__entry->prog_id	= xdp->aux->id;
 		__entry->act		= XDP_REDIRECT;
 		__entry->ifindex	= dev->ifindex;
 		__entry->err		= err;
-		__entry->to_ifindex	= map ? devmap_ifindex(tgt, map) :
-						index;
-		__entry->map_id		= map ? map->id : 0;
-		__entry->map_index	= map ? index : 0;
+		__entry->to_ifindex	= ifindex;
+		__entry->map_id		= map_id;
+		__entry->map_index	= map_index;
 	),
 
 	TP_printk("prog_id=%d action=%s ifindex=%d to_ifindex=%d err=%d"
@@ -133,45 +137,49 @@ DEFINE_EVENT(xdp_redirect_template, xdp_redirect,
 	TP_PROTO(const struct net_device *dev,
 		 const struct bpf_prog *xdp,
 		 const void *tgt, int err,
-		 const struct bpf_map *map, u32 index),
-	TP_ARGS(dev, xdp, tgt, err, map, index)
+		 enum bpf_map_type map_type,
+		 u32 map_id, u32 index),
+	TP_ARGS(dev, xdp, tgt, err, map_type, map_id, index)
 );
 
 DEFINE_EVENT(xdp_redirect_template, xdp_redirect_err,
 	TP_PROTO(const struct net_device *dev,
 		 const struct bpf_prog *xdp,
 		 const void *tgt, int err,
-		 const struct bpf_map *map, u32 index),
-	TP_ARGS(dev, xdp, tgt, err, map, index)
+		 enum bpf_map_type map_type,
+		 u32 map_id, u32 index),
+	TP_ARGS(dev, xdp, tgt, err, map_type, map_id, index)
 );
 
-#define _trace_xdp_redirect(dev, xdp, to)				\
-	 trace_xdp_redirect(dev, xdp, NULL, 0, NULL, to)
+#define _trace_xdp_redirect(dev, xdp, to)						\
+	 trace_xdp_redirect(dev, xdp, NULL, 0, BPF_MAP_TYPE_UNSPEC, INT_MAX, to)
 
-#define _trace_xdp_redirect_err(dev, xdp, to, err)			\
-	 trace_xdp_redirect_err(dev, xdp, NULL, err, NULL, to)
+#define _trace_xdp_redirect_err(dev, xdp, to, err)					\
+	 trace_xdp_redirect_err(dev, xdp, NULL, err, BPF_MAP_TYPE_UNSPEC, INT_MAX, to)
 
-#define _trace_xdp_redirect_map(dev, xdp, to, map, index)		\
-	 trace_xdp_redirect(dev, xdp, to, 0, map, index)
+#define _trace_xdp_redirect_map(dev, xdp, to, map_type, map_id, index) \
+	 trace_xdp_redirect(dev, xdp, to, 0, map_type, map_id, index)
 
-#define _trace_xdp_redirect_map_err(dev, xdp, to, map, index, err)	\
-	 trace_xdp_redirect_err(dev, xdp, to, err, map, index)
+#define _trace_xdp_redirect_map_err(dev, xdp, to, map_type, map_id, index, err) \
+	 trace_xdp_redirect_err(dev, xdp, to, err, map_type, map_id, index)
 
 /* not used anymore, but kept around so as not to break old programs */
 DEFINE_EVENT(xdp_redirect_template, xdp_redirect_map,
 	TP_PROTO(const struct net_device *dev,
 		 const struct bpf_prog *xdp,
 		 const void *tgt, int err,
-		 const struct bpf_map *map, u32 index),
-	TP_ARGS(dev, xdp, tgt, err, map, index)
+		 enum bpf_map_type map_type,
+		 u32 map_id, u32 index),
+	TP_ARGS(dev, xdp, tgt, err, map_type, map_id, index)
 );
 
 DEFINE_EVENT(xdp_redirect_template, xdp_redirect_map_err,
 	TP_PROTO(const struct net_device *dev,
 		 const struct bpf_prog *xdp,
 		 const void *tgt, int err,
-		 const struct bpf_map *map, u32 index),
-	TP_ARGS(dev, xdp, tgt, err, map, index)
+		 enum bpf_map_type map_type,
+		 u32 map_id, u32 index),
+	TP_ARGS(dev, xdp, tgt, err, map_type, map_id, index)
 );
 
 TRACE_EVENT(xdp_cpumap_kthread,
diff --git a/kernel/bpf/cpumap.c b/kernel/bpf/cpumap.c
index 7352d4160b7f..0cf2791d5099 100644
--- a/kernel/bpf/cpumap.c
+++ b/kernel/bpf/cpumap.c
@@ -543,7 +543,6 @@ static void cpu_map_free(struct bpf_map *map)
 	 * complete.
 	 */
 
-	bpf_clear_redirect_map(map);
 	synchronize_rcu();
 
 	/* For cpu_map the remote CPUs can still be using the entries
diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
index f7f42448259f..7a5ad7331c3b 100644
--- a/kernel/bpf/devmap.c
+++ b/kernel/bpf/devmap.c
@@ -197,7 +197,6 @@ static void dev_map_free(struct bpf_map *map)
 	list_del_rcu(&dtab->list);
 	spin_unlock(&dev_map_lock);
 
-	bpf_clear_redirect_map(map);
 	synchronize_rcu();
 
 	/* Make sure prior __dev_map_entry_free() have completed. */
diff --git a/net/core/filter.c b/net/core/filter.c
index 183b0aa6b027..b6732000d8a2 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -3918,23 +3918,6 @@ static const struct bpf_func_proto bpf_xdp_adjust_meta_proto = {
 	.arg2_type	= ARG_ANYTHING,
 };
 
-static int __bpf_tx_xdp_map(struct net_device *dev_rx, void *fwd,
-			    struct bpf_map *map, struct xdp_buff *xdp)
-{
-	switch (map->map_type) {
-	case BPF_MAP_TYPE_DEVMAP:
-	case BPF_MAP_TYPE_DEVMAP_HASH:
-		return dev_map_enqueue(fwd, xdp, dev_rx);
-	case BPF_MAP_TYPE_CPUMAP:
-		return cpu_map_enqueue(fwd, xdp, dev_rx);
-	case BPF_MAP_TYPE_XSKMAP:
-		return __xsk_map_redirect(fwd, xdp);
-	default:
-		return -EBADRQC;
-	}
-	return 0;
-}
-
 void xdp_do_flush(void)
 {
 	__dev_flush();
@@ -3943,55 +3926,52 @@ void xdp_do_flush(void)
 }
 EXPORT_SYMBOL_GPL(xdp_do_flush);
 
-void bpf_clear_redirect_map(struct bpf_map *map)
-{
-	struct bpf_redirect_info *ri;
-	int cpu;
-
-	for_each_possible_cpu(cpu) {
-		ri = per_cpu_ptr(&bpf_redirect_info, cpu);
-		/* Avoid polluting remote cacheline due to writes if
-		 * not needed. Once we pass this test, we need the
-		 * cmpxchg() to make sure it hasn't been changed in
-		 * the meantime by remote CPU.
-		 */
-		if (unlikely(READ_ONCE(ri->map) == map))
-			cmpxchg(&ri->map, map, NULL);
-	}
-}
-
 int xdp_do_redirect(struct net_device *dev, struct xdp_buff *xdp,
 		    struct bpf_prog *xdp_prog)
 {
 	struct bpf_redirect_info *ri = this_cpu_ptr(&bpf_redirect_info);
-	struct bpf_map *map = READ_ONCE(ri->map);
-	u32 index = ri->tgt_index;
+	enum bpf_map_type map_type = ri->map_type;
 	void *fwd = ri->tgt_value;
+	u32 map_id = ri->map_id;
 	int err;
 
-	ri->tgt_index = 0;
-	ri->tgt_value = NULL;
-	WRITE_ONCE(ri->map, NULL);
+	ri->map_id = 0; /* Valid map id idr range: [1,INT_MAX[ */
+	ri->map_type = BPF_MAP_TYPE_UNSPEC;
 
-	if (unlikely(!map)) {
-		fwd = dev_get_by_index_rcu(dev_net(dev), index);
-		if (unlikely(!fwd)) {
-			err = -EINVAL;
-			goto err;
+	switch (map_type) {
+	case BPF_MAP_TYPE_DEVMAP:
+		fallthrough;
+	case BPF_MAP_TYPE_DEVMAP_HASH:
+		err = dev_map_enqueue(fwd, xdp, dev);
+		break;
+	case BPF_MAP_TYPE_CPUMAP:
+		err = cpu_map_enqueue(fwd, xdp, dev);
+		break;
+	case BPF_MAP_TYPE_XSKMAP:
+		err = __xsk_map_redirect(fwd, xdp);
+		break;
+	case BPF_MAP_TYPE_UNSPEC:
+		if (map_id == INT_MAX) {
+			fwd = dev_get_by_index_rcu(dev_net(dev), ri->tgt_index);
+			if (unlikely(!fwd)) {
+				err = -EINVAL;
+				break;
+			}
+			err = dev_xdp_enqueue(fwd, xdp, dev);
+			break;
 		}
-
-		err = dev_xdp_enqueue(fwd, xdp, dev);
-	} else {
-		err = __bpf_tx_xdp_map(dev, fwd, map, xdp);
+		fallthrough;
+	default:
+		err = -EBADRQC;
 	}
 
 	if (unlikely(err))
 		goto err;
 
-	_trace_xdp_redirect_map(dev, xdp_prog, fwd, map, index);
+	_trace_xdp_redirect_map(dev, xdp_prog, fwd, map_type, map_id, ri->tgt_index);
 	return 0;
 err:
-	_trace_xdp_redirect_map_err(dev, xdp_prog, fwd, map, index, err);
+	_trace_xdp_redirect_map_err(dev, xdp_prog, fwd, map_type, map_id, ri->tgt_index, err);
 	return err;
 }
 EXPORT_SYMBOL_GPL(xdp_do_redirect);
@@ -4000,41 +3980,36 @@ static int xdp_do_generic_redirect_map(struct net_device *dev,
 				       struct sk_buff *skb,
 				       struct xdp_buff *xdp,
 				       struct bpf_prog *xdp_prog,
-				       struct bpf_map *map)
+				       void *fwd,
+				       enum bpf_map_type map_type, u32 map_id)
 {
 	struct bpf_redirect_info *ri = this_cpu_ptr(&bpf_redirect_info);
-	u32 index = ri->tgt_index;
-	void *fwd = ri->tgt_value;
-	int err = 0;
-
-	ri->tgt_index = 0;
-	ri->tgt_value = NULL;
-	WRITE_ONCE(ri->map, NULL);
-
-	if (map->map_type == BPF_MAP_TYPE_DEVMAP ||
-	    map->map_type == BPF_MAP_TYPE_DEVMAP_HASH) {
-		struct bpf_dtab_netdev *dst = fwd;
+	int err;
 
-		err = dev_map_generic_redirect(dst, skb, xdp_prog);
+	switch (map_type) {
+	case BPF_MAP_TYPE_DEVMAP:
+		fallthrough;
+	case BPF_MAP_TYPE_DEVMAP_HASH:
+		err = dev_map_generic_redirect(fwd, skb, xdp_prog);
 		if (unlikely(err))
 			goto err;
-	} else if (map->map_type == BPF_MAP_TYPE_XSKMAP) {
-		struct xdp_sock *xs = fwd;
-
-		err = xsk_generic_rcv(xs, xdp);
+		break;
+	case BPF_MAP_TYPE_XSKMAP:
+		err = xsk_generic_rcv(fwd, xdp);
 		if (err)
 			goto err;
 		consume_skb(skb);
-	} else {
+		break;
+	default:
 		/* TODO: Handle BPF_MAP_TYPE_CPUMAP */
 		err = -EBADRQC;
 		goto err;
 	}
 
-	_trace_xdp_redirect_map(dev, xdp_prog, fwd, map, index);
+	_trace_xdp_redirect_map(dev, xdp_prog, fwd, map_type, map_id, ri->tgt_index);
 	return 0;
 err:
-	_trace_xdp_redirect_map_err(dev, xdp_prog, fwd, map, index, err);
+	_trace_xdp_redirect_map_err(dev, xdp_prog, fwd, map_type, map_id, ri->tgt_index, err);
 	return err;
 }
 
@@ -4042,31 +4017,34 @@ int xdp_do_generic_redirect(struct net_device *dev, struct sk_buff *skb,
 			    struct xdp_buff *xdp, struct bpf_prog *xdp_prog)
 {
 	struct bpf_redirect_info *ri = this_cpu_ptr(&bpf_redirect_info);
-	struct bpf_map *map = READ_ONCE(ri->map);
-	u32 index = ri->tgt_index;
-	struct net_device *fwd;
-	int err = 0;
-
-	if (map)
-		return xdp_do_generic_redirect_map(dev, skb, xdp, xdp_prog,
-						   map);
-	ri->tgt_index = 0;
-	fwd = dev_get_by_index_rcu(dev_net(dev), index);
-	if (unlikely(!fwd)) {
-		err = -EINVAL;
-		goto err;
-	}
+	enum bpf_map_type map_type = ri->map_type;
+	void *fwd = ri->tgt_value;
+	u32 map_id = ri->map_id;
+	int err;
 
-	err = xdp_ok_fwd_dev(fwd, skb->len);
-	if (unlikely(err))
-		goto err;
+	ri->map_id = 0; /* Valid map id idr range: [1,INT_MAX[ */
+	ri->map_type = BPF_MAP_TYPE_UNSPEC;
 
-	skb->dev = fwd;
-	_trace_xdp_redirect(dev, xdp_prog, index);
-	generic_xdp_tx(skb, xdp_prog);
-	return 0;
+	if (map_type == BPF_MAP_TYPE_UNSPEC && map_id == INT_MAX) {
+		fwd = dev_get_by_index_rcu(dev_net(dev), ri->tgt_index);
+		if (unlikely(!fwd)) {
+			err = -EINVAL;
+			goto err;
+		}
+
+		err = xdp_ok_fwd_dev(fwd, skb->len);
+		if (unlikely(err))
+			goto err;
+
+		skb->dev = fwd;
+		_trace_xdp_redirect(dev, xdp_prog, ri->tgt_index);
+		generic_xdp_tx(skb, xdp_prog);
+		return 0;
+	}
+
+	return xdp_do_generic_redirect_map(dev, skb, xdp, xdp_prog, fwd, map_type, map_id);
 err:
-	_trace_xdp_redirect_err(dev, xdp_prog, index, err);
+	_trace_xdp_redirect_err(dev, xdp_prog, ri->tgt_index, err);
 	return err;
 }
 
@@ -4077,10 +4055,12 @@ BPF_CALL_2(bpf_xdp_redirect, u32, ifindex, u64, flags)
 	if (unlikely(flags))
 		return XDP_ABORTED;
 
-	ri->flags = flags;
+	/* NB! Map type UNSPEC and map_id == INT_MAX (never generated
+	 * by map_idr) is used for ifindex based XDP redirect.
+	 */
 	ri->tgt_index = ifindex;
-	ri->tgt_value = NULL;
-	WRITE_ONCE(ri->map, NULL);
+	ri->map_id = INT_MAX;
+	ri->map_type = BPF_MAP_TYPE_UNSPEC;
 
 	return XDP_REDIRECT;
 }
diff --git a/net/xdp/xskmap.c b/net/xdp/xskmap.c
index fbeb4870f798..67b4ce504852 100644
--- a/net/xdp/xskmap.c
+++ b/net/xdp/xskmap.c
@@ -87,7 +87,6 @@ static void xsk_map_free(struct bpf_map *map)
 {
 	struct xsk_map *m = container_of(map, struct xsk_map, map);
 
-	bpf_clear_redirect_map(map);
 	synchronize_net();
 	bpf_map_area_free(m);
 }
-- 
2.27.0

Re: [PATCH bpf-next v6 0/2] Optimize bpf_redirect_map()/xdp_do_redirect()

[Daniel Borkmann]

On 3/8/21 12:29 PM, Björn Töpel wrote:
> Hi XDP-folks,
> 
> This two patch series contain two optimizations for the
> bpf_redirect_map() helper and the xdp_do_redirect() function.
> 
> The bpf_redirect_map() optimization is about avoiding the map lookup
> dispatching. Instead of having a switch-statement and selecting the
> correct lookup function, we let bpf_redirect_map() be a map operation,
> where each map has its own bpf_redirect_map() implementation. This way
> the run-time lookup is avoided.
> 
> The xdp_do_redirect() patch restructures the code, so that the map
> pointer indirection can be avoided.
> 
> Performance-wise I got 4% improvement for XSKMAP
> (sample:xdpsock/rx-drop), and 8% (sample:xdp_redirect_map) on my
> machine.
> 
> @Jesper/@Toke I kept your Acked-by: for patch 2. Let me know, if you
> don't agree with that decision.
> 
> More details in each commit.
> 
> Changelog:
> v5->v6:  Removed REDIR enum, and instead use map_id and map_type. (Daniel)
>           Applied Daniel's fixups on patch 1. (Daniel)
> v4->v5:  Renamed map operation to map_redirect. (Daniel)
> v3->v4:  Made bpf_redirect_map() a map operation. (Daniel)
> v2->v3:  Fix build when CONFIG_NET is not set. (lkp)
> v1->v2:  Removed warning when CONFIG_BPF_SYSCALL was not set. (lkp)
>           Cleaned up case-clause in xdp_do_generic_redirect_map(). (Toke)
>           Re-added comment. (Toke)
> rfc->v1: Use map_id, and remove bpf_clear_redirect_map(). (Toke)
>           Get rid of the macro and use __always_inline. (Jesper)

Applied, thanks!

Re: [PATCH bpf-next v6 0/2] Optimize bpf_redirect_map()/xdp_do_redirect()

[patchwork-bot+netdevbpf]

Hello:

This series was applied to bpf/bpf-next.git (refs/heads/master):

On Mon,  8 Mar 2021 12:29:05 +0100 you wrote:
> Hi XDP-folks,
> 
> This two patch series contain two optimizations for the
> bpf_redirect_map() helper and the xdp_do_redirect() function.
> 
> The bpf_redirect_map() optimization is about avoiding the map lookup
> dispatching. Instead of having a switch-statement and selecting the
> correct lookup function, we let bpf_redirect_map() be a map operation,
> where each map has its own bpf_redirect_map() implementation. This way
> the run-time lookup is avoided.
> 
> [...]

Here is the summary with links:
  - [bpf-next,v6,1/2] bpf, xdp: make bpf_redirect_map() a map operation
    https://git.kernel.org/bpf/bpf-next/c/e6a4750ffe9d
  - [bpf-next,v6,2/2] bpf, xdp: restructure redirect actions
    https://git.kernel.org/bpf/bpf-next/c/ee75aef23afe

You are awesome, thank you!
--
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html