bpf: Add BPF_F_CPU and BPF_F_ALL_CPUS flags support for percpu_hash and lru_percpu_hash maps

Introduce BPF_F_ALL_CPUS flag support for percpu_hash and lru_percpu_hash
maps to allow updating values for all CPUs with a single value for both
update_elem and update_batch APIs.

Introduce BPF_F_CPU flag support for percpu_hash and lru_percpu_hash
maps to allow:

* update value for specified CPU for both update_elem and update_batch
APIs.
* lookup value for specified CPU for both lookup_elem and lookup_batch
APIs.

The BPF_F_CPU flag is passed via:

* map_flags along with embedded cpu info.
* elem_flags along with embedded cpu info.

Signed-off-by: Leon Hwang <[email protected]>

Author: Asphaltt

include/linux/bpf.h

@@ -2697,7 +2697,7 @@ int map_set_for_each_callback_args(struct bpf_verifier_env *env,
 				   struct bpf_func_state *caller,
 				   struct bpf_func_state *callee);
 
-int bpf_percpu_hash_copy(struct bpf_map *map, void *key, void *value);
+int bpf_percpu_hash_copy(struct bpf_map *map, void *key, void *value, u64 flags);
 int bpf_percpu_array_copy(struct bpf_map *map, void *key, void *value, u64 flags);
 int bpf_percpu_hash_update(struct bpf_map *map, void *key, void *value,
 			   u64 flags);
@@ -3720,6 +3720,8 @@ static inline bool bpf_map_supports_cpu_flags(enum bpf_map_type map_type)
 {
 	switch (map_type) {
 	case BPF_MAP_TYPE_PERCPU_ARRAY:
+	case BPF_MAP_TYPE_PERCPU_HASH:
+	case BPF_MAP_TYPE_LRU_PERCPU_HASH:
 		return true;
 	default:
 		return false;

kernel/bpf/hashtab.c

@@ -937,7 +937,7 @@ static void free_htab_elem(struct bpf_htab *htab, struct htab_elem *l)
 }
 
 static void pcpu_copy_value(struct bpf_htab *htab, void __percpu *pptr,
-			    void *value, bool onallcpus)
+			    void *value, bool onallcpus, u64 map_flags)
 {
 	if (!onallcpus) {
 		/* copy true value_size bytes */
@@ -946,15 +946,26 @@ static void pcpu_copy_value(struct bpf_htab *htab, void __percpu *pptr,
 		u32 size = round_up(htab->map.value_size, 8);
 		int off = 0, cpu;
 
+		if (map_flags & BPF_F_CPU) {
+			cpu = map_flags >> 32;
+			copy_map_value_long(&htab->map, per_cpu_ptr(pptr, cpu), value);
+			return;
+		}
+
 		for_each_possible_cpu(cpu) {
 			copy_map_value_long(&htab->map, per_cpu_ptr(pptr, cpu), value + off);
-			off += size;
+			/* same user-provided value is used if BPF_F_ALL_CPUS
+			 * is specified, otherwise value is an array of per-CPU
+			 * values.
+			 */
+			if (!(map_flags & BPF_F_ALL_CPUS))
+				off += size;
 		}
 	}
 }
 
 static void pcpu_init_value(struct bpf_htab *htab, void __percpu *pptr,
-			    void *value, bool onallcpus)
+			    void *value, bool onallcpus, u64 map_flags)
 {
 	/* When not setting the initial value on all cpus, zero-fill element
 	 * values for other cpus. Otherwise, bpf program has no way to ensure
@@ -972,7 +983,7 @@ static void pcpu_init_value(struct bpf_htab *htab, void __percpu *pptr,
 				zero_map_value(&htab->map, per_cpu_ptr(pptr, cpu));
 		}
 	} else {
-		pcpu_copy_value(htab, pptr, value, onallcpus);
+		pcpu_copy_value(htab, pptr, value, onallcpus, map_flags);
 	}
 }
 
@@ -984,7 +995,7 @@ static bool fd_htab_map_needs_adjust(const struct bpf_htab *htab)
 static struct htab_elem *alloc_htab_elem(struct bpf_htab *htab, void *key,
 					 void *value, u32 key_size, u32 hash,
 					 bool percpu, bool onallcpus,
-					 struct htab_elem *old_elem)
+					 struct htab_elem *old_elem, u64 map_flags)
 {
 	u32 size = htab->map.value_size;
 	bool prealloc = htab_is_prealloc(htab);
@@ -1042,7 +1053,7 @@ static struct htab_elem *alloc_htab_elem(struct bpf_htab *htab, void *key,
 			pptr = *(void __percpu **)ptr;
 		}
 
-		pcpu_init_value(htab, pptr, value, onallcpus);
+		pcpu_init_value(htab, pptr, value, onallcpus, map_flags);
 
 		if (!prealloc)
 			htab_elem_set_ptr(l_new, key_size, pptr);
@@ -1147,7 +1158,7 @@ static long htab_map_update_elem(struct bpf_map *map, void *key, void *value,
 	}
 
 	l_new = alloc_htab_elem(htab, key, value, key_size, hash, false, false,
-				l_old);
+				l_old, map_flags);
 	if (IS_ERR(l_new)) {
 		/* all pre-allocated elements are in use or memory exhausted */
 		ret = PTR_ERR(l_new);
@@ -1263,7 +1274,7 @@ static long htab_map_update_elem_in_place(struct bpf_map *map, void *key,
 	u32 key_size, hash;
 	int ret;
 
-	if (unlikely(map_flags > BPF_EXIST))
+	if (unlikely(!onallcpus && map_flags > BPF_EXIST))
 		/* unknown flags */
 		return -EINVAL;
 
@@ -1291,7 +1302,7 @@ static long htab_map_update_elem_in_place(struct bpf_map *map, void *key,
 		/* Update value in-place */
 		if (percpu) {
 			pcpu_copy_value(htab, htab_elem_get_ptr(l_old, key_size),
-					value, onallcpus);
+					value, onallcpus, map_flags);
 		} else {
 			void **inner_map_pptr = htab_elem_value(l_old, key_size);
 
@@ -1300,7 +1311,7 @@ static long htab_map_update_elem_in_place(struct bpf_map *map, void *key,
 		}
 	} else {
 		l_new = alloc_htab_elem(htab, key, value, key_size,
-					hash, percpu, onallcpus, NULL);
+					hash, percpu, onallcpus, NULL, map_flags);
 		if (IS_ERR(l_new)) {
 			ret = PTR_ERR(l_new);
 			goto err;
@@ -1326,7 +1337,7 @@ static long __htab_lru_percpu_map_update_elem(struct bpf_map *map, void *key,
 	u32 key_size, hash;
 	int ret;
 
-	if (unlikely(map_flags > BPF_EXIST))
+	if (unlikely(!onallcpus && map_flags > BPF_EXIST))
 		/* unknown flags */
 		return -EINVAL;
 
@@ -1366,10 +1377,10 @@ static long __htab_lru_percpu_map_update_elem(struct bpf_map *map, void *key,
 
 		/* per-cpu hash map can update value in-place */
 		pcpu_copy_value(htab, htab_elem_get_ptr(l_old, key_size),
-				value, onallcpus);
+				value, onallcpus, map_flags);
 	} else {
 		pcpu_init_value(htab, htab_elem_get_ptr(l_new, key_size),
-				value, onallcpus);
+				value, onallcpus, map_flags);
 		hlist_nulls_add_head_rcu(&l_new->hash_node, head);
 		l_new = NULL;
 	}
@@ -1698,9 +1709,16 @@ __htab_map_lookup_and_delete_batch(struct bpf_map *map,
 	int ret = 0;
 
 	elem_map_flags = attr->batch.elem_flags;
-	if ((elem_map_flags & ~BPF_F_LOCK) ||
-	    ((elem_map_flags & BPF_F_LOCK) && !btf_record_has_field(map->record, BPF_SPIN_LOCK)))
-		return -EINVAL;
+	if (!do_delete && is_percpu) {
+		ret = bpf_map_check_op_flags(map, elem_map_flags, BPF_F_LOCK | BPF_F_CPU);
+		if (ret)
+			return ret;
+	} else {
+		if ((elem_map_flags & ~BPF_F_LOCK) ||
+		    ((elem_map_flags & BPF_F_LOCK) &&
+		     !btf_record_has_field(map->record, BPF_SPIN_LOCK)))
+			return -EINVAL;
+	}
 
 	map_flags = attr->batch.flags;
 	if (map_flags)
@@ -1724,7 +1742,7 @@ __htab_map_lookup_and_delete_batch(struct bpf_map *map,
 	value_size = htab->map.value_size;
 	size = round_up(value_size, 8);
 	if (is_percpu)
-		value_size = size * num_possible_cpus();
+		value_size = (elem_map_flags & BPF_F_CPU) ? size : size * num_possible_cpus();
 	total = 0;
 	/* while experimenting with hash tables with sizes ranging from 10 to
 	 * 1000, it was observed that a bucket can have up to 5 entries.
@@ -1806,10 +1824,17 @@ __htab_map_lookup_and_delete_batch(struct bpf_map *map,
 			void __percpu *pptr;
 
 			pptr = htab_elem_get_ptr(l, map->key_size);
-			for_each_possible_cpu(cpu) {
-				copy_map_value_long(&htab->map, dst_val + off, per_cpu_ptr(pptr, cpu));
-				check_and_init_map_value(&htab->map, dst_val + off);
-				off += size;
+			if (elem_map_flags & BPF_F_CPU) {
+				cpu = elem_map_flags >> 32;
+				copy_map_value_long(&htab->map, dst_val, per_cpu_ptr(pptr, cpu));
+				check_and_init_map_value(&htab->map, dst_val);
+			} else {
+				for_each_possible_cpu(cpu) {
+					copy_map_value_long(&htab->map, dst_val + off,
+							    per_cpu_ptr(pptr, cpu));
+					check_and_init_map_value(&htab->map, dst_val + off);
+					off += size;
+				}
 			}
 		} else {
 			value = htab_elem_value(l, key_size);
@@ -2365,7 +2390,7 @@ static void *htab_lru_percpu_map_lookup_percpu_elem(struct bpf_map *map, void *k
 	return NULL;
 }
 
-int bpf_percpu_hash_copy(struct bpf_map *map, void *key, void *value)
+int bpf_percpu_hash_copy(struct bpf_map *map, void *key, void *value, u64 map_flags)
 {
 	struct htab_elem *l;
 	void __percpu *pptr;
@@ -2382,16 +2407,22 @@ int bpf_percpu_hash_copy(struct bpf_map *map, void *key, void *value)
 	l = __htab_map_lookup_elem(map, key);
 	if (!l)
 		goto out;
+	ret = 0;
 	/* We do not mark LRU map element here in order to not mess up
 	 * eviction heuristics when user space does a map walk.
 	 */
 	pptr = htab_elem_get_ptr(l, map->key_size);
+	if (map_flags & BPF_F_CPU) {
+		cpu = map_flags >> 32;
+		copy_map_value_long(map, value, per_cpu_ptr(pptr, cpu));
+		check_and_init_map_value(map, value);
+		goto out;
+	}
 	for_each_possible_cpu(cpu) {
 		copy_map_value_long(map, value + off, per_cpu_ptr(pptr, cpu));
 		check_and_init_map_value(map, value + off);
 		off += size;
 	}
-	ret = 0;
 out:
 	rcu_read_unlock();
 	return ret;

kernel/bpf/syscall.c

@@ -314,7 +314,7 @@ static int bpf_map_copy_value(struct bpf_map *map, void *key, void *value,
 	bpf_disable_instrumentation();
 	if (map->map_type == BPF_MAP_TYPE_PERCPU_HASH ||
 	    map->map_type == BPF_MAP_TYPE_LRU_PERCPU_HASH) {
-		err = bpf_percpu_hash_copy(map, key, value);
+		err = bpf_percpu_hash_copy(map, key, value, flags);
 	} else if (map->map_type == BPF_MAP_TYPE_PERCPU_ARRAY) {
 		err = bpf_percpu_array_copy(map, key, value, flags);
 	} else if (map->map_type == BPF_MAP_TYPE_PERCPU_CGROUP_STORAGE) {