From: Leon Hwang <leon.hwang@linux.dev>
To: bpf@vger.kernel.org
Cc: ast@kernel.org, andrii@kernel.org, daniel@iogearbox.net,
olsajiri@gmail.com, yonghong.song@linux.dev, song@kernel.org,
eddyz87@gmail.com, dxu@dxuuu.xyz, deso@posteo.net,
leon.hwang@linux.dev, kernel-patches-bot@fb.com
Subject: [PATCH bpf-next v3 3/6] bpf: Introduce BPF_F_CPU flag for percpu_hash and lru_percpu_hash maps
Date: Fri, 22 Aug 2025 00:08:14 +0800 [thread overview]
Message-ID: <20250821160817.70285-4-leon.hwang@linux.dev> (raw)
In-Reply-To: <20250821160817.70285-1-leon.hwang@linux.dev>
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.
Introduce BPF_F_CPU flag support for percpu_hash and lru_percpu_hash
maps to allow updating value for specified CPU.
This enhancement enables:
* Efficient update values across all CPUs with a single value when
BPF_F_ALL_CPUS is set for update_elem and update_batch APIs.
* Targeted update or lookup for a specified CPU when BPF_F_CPU is set.
The BPF_F_CPU flag is passed via:
* map_flags of lookup_elem and update_elem APIs along with embedded cpu
field.
* elem_flags of lookup_batch and update_batch APIs along with embedded
cpu field.
Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
---
include/linux/bpf.h | 54 +++++++++++++++++++-
kernel/bpf/arraymap.c | 29 ++++-------
kernel/bpf/hashtab.c | 111 +++++++++++++++++++++++++++++-------------
kernel/bpf/syscall.c | 30 +++---------
4 files changed, 147 insertions(+), 77 deletions(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index b2191b1e455a6..dc715eef9cbf4 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -2696,7 +2696,7 @@ 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,
@@ -3710,4 +3710,56 @@ int bpf_prog_get_file_line(struct bpf_prog *prog, unsigned long ip, const char *
const char **linep, int *nump);
struct bpf_prog *bpf_prog_find_from_stack(void);
+static inline int bpf_map_check_cpu_flags(u64 flags, bool check_all_cpus)
+{
+ const u64 cpu_flags = BPF_F_CPU | BPF_F_ALL_CPUS;
+ u32 cpu;
+
+ if (check_all_cpus) {
+ if (unlikely((u32)flags > BPF_F_ALL_CPUS))
+ /* unknown flags */
+ return -EINVAL;
+ if (unlikely((flags & cpu_flags) == cpu_flags))
+ return -EINVAL;
+ } else {
+ if (unlikely((u32)flags & ~BPF_F_CPU))
+ return -EINVAL;
+ }
+
+ cpu = flags >> 32;
+ if (unlikely((flags & BPF_F_CPU) && cpu >= num_possible_cpus()))
+ return -ERANGE;
+
+ return 0;
+}
+
+static inline bool bpf_map_support_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;
+ }
+}
+
+static inline int bpf_map_check_flags(struct bpf_map *map, u64 flags, bool check_flag)
+{
+ if (check_flag && ((u32)flags & ~(BPF_F_LOCK | BPF_F_CPU | BPF_F_ALL_CPUS)))
+ return -EINVAL;
+
+ if ((flags & BPF_F_LOCK) && !btf_record_has_field(map->record, BPF_SPIN_LOCK))
+ return -EINVAL;
+
+ if (!(flags & BPF_F_CPU) && flags >> 32)
+ return -EINVAL;
+
+ if ((flags & (BPF_F_CPU | BPF_F_ALL_CPUS)) && !bpf_map_support_cpu_flags(map->map_type))
+ return -EINVAL;
+
+ return 0;
+}
+
#endif /* _LINUX_BPF_H */
diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
index 1efa730105e24..f7646bcabb3c8 100644
--- a/kernel/bpf/arraymap.c
+++ b/kernel/bpf/arraymap.c
@@ -300,18 +300,15 @@ int bpf_percpu_array_copy(struct bpf_map *map, void *key, void *value, u64 flags
struct bpf_array *array = container_of(map, struct bpf_array, map);
u32 index = *(u32 *)key;
void __percpu *pptr;
+ int off = 0, err;
u32 size, cpu;
- int off = 0;
if (unlikely(index >= array->map.max_entries))
return -ENOENT;
- if (unlikely((u32)flags & ~BPF_F_CPU))
- return -EINVAL;
-
- cpu = flags >> 32;
- if (unlikely((flags & BPF_F_CPU) && cpu >= num_possible_cpus()))
- return -ERANGE;
+ err = bpf_map_check_cpu_flags(flags, false);
+ if (unlikely(err))
+ return err;
/* per_cpu areas are zero-filled and bpf programs can only
* access 'value_size' of them, so copying rounded areas
@@ -321,6 +318,7 @@ int bpf_percpu_array_copy(struct bpf_map *map, void *key, void *value, u64 flags
rcu_read_lock();
pptr = array->pptrs[index & array->index_mask];
if (flags & BPF_F_CPU) {
+ cpu = flags >> 32;
copy_map_value_long(map, value, per_cpu_ptr(pptr, cpu));
check_and_init_map_value(map, value);
} else {
@@ -397,22 +395,14 @@ int bpf_percpu_array_update(struct bpf_map *map, void *key, void *value,
u64 map_flags)
{
struct bpf_array *array = container_of(map, struct bpf_array, map);
- const u64 cpu_flags = BPF_F_CPU | BPF_F_ALL_CPUS;
u32 index = *(u32 *)key;
void __percpu *pptr;
+ int off = 0, err;
u32 size, cpu;
- int off = 0;
-
- if (unlikely((u32)map_flags > BPF_F_ALL_CPUS))
- /* unknown flags */
- return -EINVAL;
- if (unlikely((map_flags & cpu_flags) == cpu_flags))
- return -EINVAL;
- cpu = map_flags >> 32;
- if (unlikely((map_flags & BPF_F_CPU) && cpu >= num_possible_cpus()))
- /* invalid cpu */
- return -ERANGE;
+ err = bpf_map_check_cpu_flags(map_flags, true);
+ if (unlikely(err))
+ return err;
if (unlikely(index >= array->map.max_entries))
/* all elements were pre-allocated, cannot insert a new one */
@@ -432,6 +422,7 @@ int bpf_percpu_array_update(struct bpf_map *map, void *key, void *value,
rcu_read_lock();
pptr = array->pptrs[index & array->index_mask];
if (map_flags & BPF_F_CPU) {
+ cpu = map_flags >> 32;
copy_map_value_long(map, per_cpu_ptr(pptr, cpu), value);
bpf_obj_free_fields(array->map.record, per_cpu_ptr(pptr, cpu));
} else {
diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
index 71f9931ac64cd..34a35cdade425 100644
--- a/kernel/bpf/hashtab.c
+++ b/kernel/bpf/hashtab.c
@@ -937,24 +937,39 @@ 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)
{
+ int cpu = map_flags & BPF_F_CPU ? map_flags >> 32 : 0;
+ int current_cpu = raw_smp_processor_id();
+
if (!onallcpus) {
/* copy true value_size bytes */
- copy_map_value(&htab->map, this_cpu_ptr(pptr), value);
+ copy_map_value(&htab->map, (map_flags & BPF_F_CPU) && cpu != current_cpu ?
+ per_cpu_ptr(pptr, cpu) : this_cpu_ptr(pptr), value);
} else {
u32 size = round_up(htab->map.value_size, 8);
- int off = 0, cpu;
+ int off = 0;
+
+ if (map_flags & BPF_F_CPU) {
+ copy_map_value_long(&htab->map, cpu != current_cpu ?
+ per_cpu_ptr(pptr, cpu) : this_cpu_ptr(pptr), 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 +987,7 @@ 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 +999,7 @@ 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 +1057,7 @@ 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 +1162,7 @@ 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);
@@ -1263,9 +1278,15 @@ 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))
- /* unknown flags */
- return -EINVAL;
+ if (percpu) {
+ ret = bpf_map_check_cpu_flags(map_flags, true);
+ if (unlikely(ret))
+ return ret;
+ } else {
+ if (unlikely(map_flags > BPF_EXIST))
+ /* unknown flags */
+ return -EINVAL;
+ }
WARN_ON_ONCE(!rcu_read_lock_held() && !rcu_read_lock_trace_held() &&
!rcu_read_lock_bh_held());
@@ -1291,7 +1312,7 @@ 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 +1321,7 @@ 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;
@@ -1326,9 +1347,9 @@ 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))
- /* unknown flags */
- return -EINVAL;
+ ret = bpf_map_check_cpu_flags(map_flags, true);
+ if (unlikely(ret))
+ return ret;
WARN_ON_ONCE(!rcu_read_lock_held() && !rcu_read_lock_trace_held() &&
!rcu_read_lock_bh_held());
@@ -1366,10 +1387,10 @@ 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 +1719,16 @@ __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_flags(map, elem_map_flags, false);
+ 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)
@@ -1806,10 +1834,17 @@ __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 (!do_delete && (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);
@@ -2365,14 +2400,18 @@ 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)
{
+ int ret, cpu, off = 0;
struct htab_elem *l;
void __percpu *pptr;
- int ret = -ENOENT;
- int cpu, off = 0;
u32 size;
+ ret = bpf_map_check_cpu_flags(map_flags, false);
+ if (unlikely(ret))
+ return ret;
+ ret = -ENOENT;
+
/* per_cpu areas are zero-filled and bpf programs can only
* access 'value_size' of them, so copying rounded areas
* will not leak any kernel data
@@ -2386,10 +2425,16 @@ int bpf_percpu_hash_copy(struct bpf_map *map, void *key, void *value)
* eviction heuristics when user space does a map walk.
*/
pptr = htab_elem_get_ptr(l, map->key_size);
- 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;
+ 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);
+ } else {
+ 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:
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 6251ac9bc7e42..430f013f38f06 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -133,7 +133,7 @@ bool bpf_map_write_active(const struct bpf_map *map)
static u32 bpf_map_value_size(const struct bpf_map *map, u64 flags)
{
- if (map->map_type == BPF_MAP_TYPE_PERCPU_ARRAY && (flags & (BPF_F_CPU | BPF_F_ALL_CPUS)))
+ if (bpf_map_support_cpu_flags(map->map_type) && (flags & (BPF_F_CPU | BPF_F_ALL_CPUS)))
return round_up(map->value_size, 8);
else if (map->map_type == BPF_MAP_TYPE_PERCPU_HASH ||
map->map_type == BPF_MAP_TYPE_LRU_PERCPU_HASH ||
@@ -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) {
@@ -1656,24 +1656,6 @@ static void *___bpf_copy_key(bpfptr_t ukey, u64 key_size)
return NULL;
}
-static int check_map_flags(struct bpf_map *map, u64 flags, bool check_flag)
-{
- if (check_flag && ((u32)flags & ~(BPF_F_LOCK | BPF_F_CPU | BPF_F_ALL_CPUS)))
- return -EINVAL;
-
- if ((flags & BPF_F_LOCK) && !btf_record_has_field(map->record, BPF_SPIN_LOCK))
- return -EINVAL;
-
- if (!(flags & BPF_F_CPU) && flags >> 32)
- return -EINVAL;
-
- if ((flags & (BPF_F_CPU | BPF_F_ALL_CPUS)) &&
- map->map_type != BPF_MAP_TYPE_PERCPU_ARRAY)
- return -EINVAL;
-
- return 0;
-}
-
/* last field in 'union bpf_attr' used by this command */
#define BPF_MAP_LOOKUP_ELEM_LAST_FIELD flags
@@ -1696,7 +1678,7 @@ static int map_lookup_elem(union bpf_attr *attr)
if (!(map_get_sys_perms(map, f) & FMODE_CAN_READ))
return -EPERM;
- err = check_map_flags(map, attr->flags, true);
+ err = bpf_map_check_flags(map, attr->flags, true);
if (err)
return err;
@@ -1761,7 +1743,7 @@ static int map_update_elem(union bpf_attr *attr, bpfptr_t uattr)
goto err_put;
}
- err = check_map_flags(map, attr->flags, false);
+ err = bpf_map_check_flags(map, attr->flags, false);
if (err)
goto err_put;
@@ -1967,7 +1949,7 @@ int generic_map_update_batch(struct bpf_map *map, struct file *map_file,
void *key, *value;
int err = 0;
- err = check_map_flags(map, attr->batch.elem_flags, true);
+ err = bpf_map_check_flags(map, attr->batch.elem_flags, true);
if (err)
return err;
@@ -2026,7 +2008,7 @@ int generic_map_lookup_batch(struct bpf_map *map,
u32 value_size, cp, max_count;
int err;
- err = check_map_flags(map, attr->batch.elem_flags, true);
+ err = bpf_map_check_flags(map, attr->batch.elem_flags, true);
if (err)
return err;
--
2.50.1
next prev parent reply other threads:[~2025-08-21 16:08 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-08-21 16:08 [PATCH bpf-next v3 0/6] Introduce BPF_F_CPU flag for percpu maps Leon Hwang
2025-08-21 16:08 ` [PATCH bpf-next v3 1/6] bpf: Introduce internal check_map_flags helper function Leon Hwang
2025-08-22 22:14 ` Andrii Nakryiko
2025-08-26 15:24 ` Leon Hwang
2025-08-26 22:50 ` Andrii Nakryiko
2025-08-21 16:08 ` [PATCH bpf-next v3 2/6] bpf: Introduce BPF_F_CPU flag for percpu_array maps Leon Hwang
2025-08-22 22:14 ` Andrii Nakryiko
2025-08-26 14:45 ` Leon Hwang
2025-08-21 16:08 ` Leon Hwang [this message]
2025-08-22 22:14 ` [PATCH bpf-next v3 3/6] bpf: Introduce BPF_F_CPU flag for percpu_hash and lru_percpu_hash maps Andrii Nakryiko
2025-08-26 15:14 ` Leon Hwang
2025-08-21 16:08 ` [PATCH bpf-next v3 4/6] bpf: Introduce BPF_F_CPU flag for percpu_cgroup_storage maps Leon Hwang
2025-08-21 16:08 ` [PATCH bpf-next v3 5/6] libbpf: Support BPF_F_CPU for percpu maps Leon Hwang
2025-08-22 22:20 ` Andrii Nakryiko
2025-08-26 15:35 ` Leon Hwang
2025-08-26 22:50 ` Andrii Nakryiko
2025-08-21 16:08 ` [PATCH bpf-next v3 6/6] selftests/bpf: Add cases to test BPF_F_CPU flag Leon Hwang
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