From: Leon Hwang <leon.hwang@linux.dev>
To: bpf@vger.kernel.org
Cc: ast@kernel.org, andrii@kernel.org, daniel@iogearbox.net,
Leon Hwang <leon.hwang@linux.dev>
Subject: [RFC PATCH bpf-next v2 1/3] bpf: Introduce BPF_F_CPU flag for percpu_array map
Date: Tue, 8 Jul 2025 00:04:02 +0800 [thread overview]
Message-ID: <20250707160404.64933-2-leon.hwang@linux.dev> (raw)
In-Reply-To: <20250707160404.64933-1-leon.hwang@linux.dev>
This patch introduces support for the BPF_F_CPU flag in percpu_array maps
to allow updating or looking up values for specified CPUs or for all CPUs
with a single value.
This enhancement enables:
* Efficient update of all CPUs using a single value when cpu == (u32)~0.
* Targeted update or lookup for a specified CPU otherwise.
The flag is passed via:
* map_flags in bpf_percpu_array_update() along with embedded cpu field.
* elem_flags in generic_map_update_batch() along with separated cpu field.
Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
---
include/linux/bpf.h | 3 +-
include/uapi/linux/bpf.h | 7 +++++
kernel/bpf/arraymap.c | 56 ++++++++++++++++++++++++++--------
kernel/bpf/syscall.c | 52 +++++++++++++++++++------------
tools/include/uapi/linux/bpf.h | 7 +++++
5 files changed, 92 insertions(+), 33 deletions(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 34dd90ec7fad..6ea5fe7fa0d5 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -2662,7 +2662,8 @@ int map_set_for_each_callback_args(struct bpf_verifier_env *env,
struct bpf_func_state *callee);
int bpf_percpu_hash_copy(struct bpf_map *map, void *key, void *value);
-int bpf_percpu_array_copy(struct bpf_map *map, void *key, void *value);
+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);
int bpf_percpu_array_update(struct bpf_map *map, void *key, void *value,
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 0670e15a6100..0d3469cb7a06 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -1371,6 +1371,12 @@ enum {
BPF_NOEXIST = 1, /* create new element if it didn't exist */
BPF_EXIST = 2, /* update existing element */
BPF_F_LOCK = 4, /* spin_lock-ed map_lookup/map_update */
+ BPF_F_CPU = 8, /* map_update for percpu_array */
+};
+
+enum {
+ /* indicate updating value across all CPUs for percpu maps. */
+ BPF_ALL_CPUS = (__u32)~0,
};
/* flags for BPF_MAP_CREATE command */
@@ -1548,6 +1554,7 @@ union bpf_attr {
__u32 map_fd;
__u64 elem_flags;
__u64 flags;
+ __u32 cpu;
} batch;
struct { /* anonymous struct used by BPF_PROG_LOAD command */
diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
index 3d080916faf9..5c5376b89930 100644
--- a/kernel/bpf/arraymap.c
+++ b/kernel/bpf/arraymap.c
@@ -295,17 +295,24 @@ static void *percpu_array_map_lookup_percpu_elem(struct bpf_map *map, void *key,
return per_cpu_ptr(array->pptrs[index & array->index_mask], cpu);
}
-int bpf_percpu_array_copy(struct bpf_map *map, void *key, void *value)
+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 cpu, off = 0;
- u32 size;
+ u32 size, cpu;
+ int off = 0;
if (unlikely(index >= array->map.max_entries))
return -ENOENT;
+ cpu = (u32)(flags >> 32);
+ flags &= (u32)~0;
+ if (unlikely(flags > BPF_F_CPU))
+ return -EINVAL;
+ if (unlikely((flags & BPF_F_CPU) && cpu >= num_possible_cpus()))
+ return -E2BIG;
+
/* 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
@@ -313,10 +320,15 @@ int bpf_percpu_array_copy(struct bpf_map *map, void *key, void *value)
size = array->elem_size;
rcu_read_lock();
pptr = array->pptrs[index & array->index_mask];
- 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 (flags & BPF_F_CPU) {
+ 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;
+ }
}
rcu_read_unlock();
return 0;
@@ -387,13 +399,21 @@ int bpf_percpu_array_update(struct bpf_map *map, void *key, void *value,
struct bpf_array *array = container_of(map, struct bpf_array, map);
u32 index = *(u32 *)key;
void __percpu *pptr;
- int cpu, off = 0;
- u32 size;
+ bool reuse_value;
+ u32 size, cpu;
+ int off = 0;
- if (unlikely(map_flags > BPF_EXIST))
+ cpu = (u32)(map_flags >> 32);
+ map_flags = map_flags & (u32)~0;
+ if (unlikely(map_flags > BPF_F_CPU))
/* unknown flags */
return -EINVAL;
+ if (unlikely((map_flags & BPF_F_CPU) && cpu != BPF_ALL_CPUS &&
+ cpu >= num_possible_cpus()))
+ /* invalid cpu */
+ return -E2BIG;
+
if (unlikely(index >= array->map.max_entries))
/* all elements were pre-allocated, cannot insert a new one */
return -E2BIG;
@@ -409,12 +429,22 @@ int bpf_percpu_array_update(struct bpf_map *map, void *key, void *value,
* so no kernel data leaks possible
*/
size = array->elem_size;
+ reuse_value = (map_flags & BPF_F_CPU) && cpu == BPF_ALL_CPUS;
rcu_read_lock();
pptr = array->pptrs[index & array->index_mask];
- for_each_possible_cpu(cpu) {
- copy_map_value_long(map, per_cpu_ptr(pptr, cpu), value + off);
+ if ((map_flags & BPF_F_CPU) && cpu != BPF_ALL_CPUS) {
+ copy_map_value_long(map, per_cpu_ptr(pptr, cpu), value);
bpf_obj_free_fields(array->map.record, per_cpu_ptr(pptr, cpu));
- off += size;
+ } else {
+ for_each_possible_cpu(cpu) {
+ if (!reuse_value) {
+ copy_map_value_long(map, per_cpu_ptr(pptr, cpu), value + off);
+ off += size;
+ } else {
+ copy_map_value_long(map, per_cpu_ptr(pptr, cpu), value);
+ }
+ bpf_obj_free_fields(array->map.record, per_cpu_ptr(pptr, cpu));
+ }
}
rcu_read_unlock();
return 0;
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 7db7182a3057..a3ce0cdecb3c 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -129,8 +129,12 @@ bool bpf_map_write_active(const struct bpf_map *map)
return atomic64_read(&map->writecnt) != 0;
}
-static u32 bpf_map_value_size(const struct bpf_map *map)
+static u32 bpf_map_value_size(const struct bpf_map *map, u64 flags)
{
+ if ((flags & BPF_F_CPU) &&
+ map->map_type == BPF_MAP_TYPE_PERCPU_ARRAY)
+ return round_up(map->value_size, 8);
+
if (map->map_type == BPF_MAP_TYPE_PERCPU_HASH ||
map->map_type == BPF_MAP_TYPE_LRU_PERCPU_HASH ||
map->map_type == BPF_MAP_TYPE_PERCPU_ARRAY ||
@@ -312,7 +316,7 @@ static int bpf_map_copy_value(struct bpf_map *map, void *key, void *value,
map->map_type == BPF_MAP_TYPE_LRU_PERCPU_HASH) {
err = bpf_percpu_hash_copy(map, key, value);
} else if (map->map_type == BPF_MAP_TYPE_PERCPU_ARRAY) {
- err = bpf_percpu_array_copy(map, key, value);
+ err = bpf_percpu_array_copy(map, key, value, flags);
} else if (map->map_type == BPF_MAP_TYPE_PERCPU_CGROUP_STORAGE) {
err = bpf_percpu_cgroup_storage_copy(map, key, value);
} else if (map->map_type == BPF_MAP_TYPE_STACK_TRACE) {
@@ -1662,7 +1666,7 @@ static int map_lookup_elem(union bpf_attr *attr)
if (CHECK_ATTR(BPF_MAP_LOOKUP_ELEM))
return -EINVAL;
- if (attr->flags & ~BPF_F_LOCK)
+ if ((attr->flags & (u32)~0) & ~(BPF_F_LOCK | BPF_F_CPU))
return -EINVAL;
CLASS(fd, f)(attr->map_fd);
@@ -1680,7 +1684,7 @@ static int map_lookup_elem(union bpf_attr *attr)
if (IS_ERR(key))
return PTR_ERR(key);
- value_size = bpf_map_value_size(map);
+ value_size = bpf_map_value_size(map, attr->flags);
err = -ENOMEM;
value = kvmalloc(value_size, GFP_USER | __GFP_NOWARN);
@@ -1749,7 +1753,7 @@ static int map_update_elem(union bpf_attr *attr, bpfptr_t uattr)
goto err_put;
}
- value_size = bpf_map_value_size(map);
+ value_size = bpf_map_value_size(map, attr->flags);
value = kvmemdup_bpfptr(uvalue, value_size);
if (IS_ERR(value)) {
err = PTR_ERR(value);
@@ -1941,19 +1945,25 @@ int generic_map_update_batch(struct bpf_map *map, struct file *map_file,
{
void __user *values = u64_to_user_ptr(attr->batch.values);
void __user *keys = u64_to_user_ptr(attr->batch.keys);
- u32 value_size, cp, max_count;
+ u32 value_size, cp, max_count, cpu = attr->batch.cpu;
+ u64 elem_flags = attr->batch.elem_flags;
void *key, *value;
int err = 0;
- if (attr->batch.elem_flags & ~BPF_F_LOCK)
+ if (elem_flags & ~(BPF_F_LOCK | BPF_F_CPU))
return -EINVAL;
- if ((attr->batch.elem_flags & BPF_F_LOCK) &&
+ if ((elem_flags & BPF_F_LOCK) &&
!btf_record_has_field(map->record, BPF_SPIN_LOCK)) {
return -EINVAL;
}
- value_size = bpf_map_value_size(map);
+ if ((elem_flags & BPF_F_CPU) &&
+ map->map_type != BPF_MAP_TYPE_PERCPU_ARRAY)
+ return -EINVAL;
+
+ value_size = bpf_map_value_size(map, elem_flags);
+ elem_flags = (((u64)cpu) << 32) | elem_flags;
max_count = attr->batch.count;
if (!max_count)
@@ -1979,8 +1989,7 @@ int generic_map_update_batch(struct bpf_map *map, struct file *map_file,
copy_from_user(value, values + cp * value_size, value_size))
break;
- err = bpf_map_update_value(map, map_file, key, value,
- attr->batch.elem_flags);
+ err = bpf_map_update_value(map, map_file, key, value, elem_flags);
if (err)
break;
@@ -2004,18 +2013,24 @@ int generic_map_lookup_batch(struct bpf_map *map,
void __user *ubatch = u64_to_user_ptr(attr->batch.in_batch);
void __user *values = u64_to_user_ptr(attr->batch.values);
void __user *keys = u64_to_user_ptr(attr->batch.keys);
+ u32 value_size, cp, max_count, cpu = attr->batch.cpu;
void *buf, *buf_prevkey, *prev_key, *key, *value;
- u32 value_size, cp, max_count;
+ u64 elem_flags = attr->batch.elem_flags;
int err;
- if (attr->batch.elem_flags & ~BPF_F_LOCK)
+ if (elem_flags & ~(BPF_F_LOCK | BPF_F_CPU))
return -EINVAL;
- if ((attr->batch.elem_flags & BPF_F_LOCK) &&
+ if ((elem_flags & BPF_F_LOCK) &&
!btf_record_has_field(map->record, BPF_SPIN_LOCK))
return -EINVAL;
- value_size = bpf_map_value_size(map);
+ if ((elem_flags & BPF_F_CPU) &&
+ map->map_type != BPF_MAP_TYPE_PERCPU_ARRAY)
+ return -EINVAL;
+
+ value_size = bpf_map_value_size(map, elem_flags);
+ elem_flags = (((u64)cpu) << 32) | elem_flags;
max_count = attr->batch.count;
if (!max_count)
@@ -2049,8 +2064,7 @@ int generic_map_lookup_batch(struct bpf_map *map,
rcu_read_unlock();
if (err)
break;
- err = bpf_map_copy_value(map, key, value,
- attr->batch.elem_flags);
+ err = bpf_map_copy_value(map, key, value, elem_flags);
if (err == -ENOENT)
goto next_key;
@@ -2137,7 +2151,7 @@ static int map_lookup_and_delete_elem(union bpf_attr *attr)
goto err_put;
}
- value_size = bpf_map_value_size(map);
+ value_size = bpf_map_value_size(map, attr->flags);
err = -ENOMEM;
value = kvmalloc(value_size, GFP_USER | __GFP_NOWARN);
@@ -5445,7 +5459,7 @@ static int bpf_task_fd_query(const union bpf_attr *attr,
return err;
}
-#define BPF_MAP_BATCH_LAST_FIELD batch.flags
+#define BPF_MAP_BATCH_LAST_FIELD batch.cpu
#define BPF_DO_BATCH(fn, ...) \
do { \
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 0670e15a6100..0d3469cb7a06 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -1371,6 +1371,12 @@ enum {
BPF_NOEXIST = 1, /* create new element if it didn't exist */
BPF_EXIST = 2, /* update existing element */
BPF_F_LOCK = 4, /* spin_lock-ed map_lookup/map_update */
+ BPF_F_CPU = 8, /* map_update for percpu_array */
+};
+
+enum {
+ /* indicate updating value across all CPUs for percpu maps. */
+ BPF_ALL_CPUS = (__u32)~0,
};
/* flags for BPF_MAP_CREATE command */
@@ -1548,6 +1554,7 @@ union bpf_attr {
__u32 map_fd;
__u64 elem_flags;
__u64 flags;
+ __u32 cpu;
} batch;
struct { /* anonymous struct used by BPF_PROG_LOAD command */
--
2.50.0
next prev parent reply other threads:[~2025-07-07 16:04 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-07-07 16:04 [RFC PATCH bpf-next v2 0/3] bpf: Introduce BPF_F_CPU flag for percpu_array map Leon Hwang
2025-07-07 16:04 ` Leon Hwang [this message]
2025-07-11 18:10 ` [RFC PATCH bpf-next v2 1/3] " Andrii Nakryiko
2025-07-14 12:47 ` Leon Hwang
2025-07-07 16:04 ` [RFC PATCH bpf-next v2 2/3] bpf, libbpf: Support BPF_F_CPU " Leon Hwang
2025-07-11 18:10 ` Andrii Nakryiko
2025-07-14 12:48 ` Leon Hwang
2025-07-07 16:04 ` [RFC PATCH bpf-next v2 3/3] selftests/bpf: Add case to test BPF_F_CPU Leon Hwang
2025-07-11 18:11 ` Andrii Nakryiko
2025-07-14 12:49 ` Leon Hwang
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