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libbpf: Add BPF_F_CPU and BPF_F_ALL_CPUS flags support for percpu maps

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Add libbpf support for the BPF_F_CPU flag for percpu maps by embedding the
cpu info into the high 32 bits of:

1. **flags**: bpf_map_lookup_elem_flags(), bpf_map__lookup_elem(),
   bpf_map_update_elem() and bpf_map__update_elem()
2. **opts->elem_flags**: bpf_map_lookup_batch() and
   bpf_map_update_batch()

And the flag can be BPF_F_ALL_CPUS, but cannot be
'BPF_F_CPU | BPF_F_ALL_CPUS'.

Behavior:

* If the flag is BPF_F_ALL_CPUS, the update is applied across all CPUs.
* If the flag is BPF_F_CPU, it updates value only to the specified CPU.
* If the flag is BPF_F_CPU, lookup value only from the specified CPU.
* lookup does not support BPF_F_ALL_CPUS.

Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
Link: https://lore.kernel.org/r/20260107022022.12843-7-leon.hwang@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Leon Hwang
2026-01-07 10:20:21 +08:00
committed by Andrii Nakryiko
parent a6d7ceaaeb
commit dc8673b28b
3 changed files with 36 additions and 19 deletions
Download Patch File Download Diff File Expand all files Collapse all files

8
src/bpf.h
View File

@@ -289,6 +289,14 @@ LIBBPF_API int bpf_map_lookup_and_delete_batch(int fd, void *in_batch,
* Update spin_lock-ed map elements. This must be
* specified if the map value contains a spinlock.
*
* **BPF_F_CPU**
* As for percpu maps, update value on the specified CPU. And the cpu
* info is embedded into the high 32 bits of **opts->elem_flags**.
*
* **BPF_F_ALL_CPUS**
* As for percpu maps, update value across all CPUs. This flag cannot
* be used with BPF_F_CPU at the same time.
*
* @param fd BPF map file descriptor
* @param keys pointer to an array of *count* keys
* @param values pointer to an array of *count* values

26
src/libbpf.c
View File

@@ -10919,7 +10919,7 @@ bpf_object__find_map_fd_by_name(const struct bpf_object *obj, const char *name)
}
static int validate_map_op(const struct bpf_map *map, size_t key_sz,
size_t value_sz, bool check_value_sz)
size_t value_sz, bool check_value_sz, __u64 flags)
{
if (!map_is_created(map)) /* map is not yet created */
return -ENOENT;
@@ -10946,6 +10946,20 @@ static int validate_map_op(const struct bpf_map *map, size_t key_sz,
int num_cpu = libbpf_num_possible_cpus();
size_t elem_sz = roundup(map->def.value_size, 8);
if (flags & (BPF_F_CPU | BPF_F_ALL_CPUS)) {
if ((flags & BPF_F_CPU) && (flags & BPF_F_ALL_CPUS)) {
pr_warn("map '%s': BPF_F_CPU and BPF_F_ALL_CPUS are mutually exclusive\n",
map->name);
return -EINVAL;
}
if (map->def.value_size != value_sz) {
pr_warn("map '%s': unexpected value size %zu provided for either BPF_F_CPU or BPF_F_ALL_CPUS, expected %u\n",
map->name, value_sz, map->def.value_size);
return -EINVAL;
}
break;
}
if (value_sz != num_cpu * elem_sz) {
pr_warn("map '%s': unexpected value size %zu provided for per-CPU map, expected %d * %zu = %zd\n",
map->name, value_sz, num_cpu, elem_sz, num_cpu * elem_sz);
@@ -10970,7 +10984,7 @@ int bpf_map__lookup_elem(const struct bpf_map *map,
{
int err;
err = validate_map_op(map, key_sz, value_sz, true);
err = validate_map_op(map, key_sz, value_sz, true, flags);
if (err)
return libbpf_err(err);
@@ -10983,7 +10997,7 @@ int bpf_map__update_elem(const struct bpf_map *map,
{
int err;
err = validate_map_op(map, key_sz, value_sz, true);
err = validate_map_op(map, key_sz, value_sz, true, flags);
if (err)
return libbpf_err(err);
@@ -10995,7 +11009,7 @@ int bpf_map__delete_elem(const struct bpf_map *map,
{
int err;
err = validate_map_op(map, key_sz, 0, false /* check_value_sz */);
err = validate_map_op(map, key_sz, 0, false /* check_value_sz */, flags);
if (err)
return libbpf_err(err);
@@ -11008,7 +11022,7 @@ int bpf_map__lookup_and_delete_elem(const struct bpf_map *map,
{
int err;
err = validate_map_op(map, key_sz, value_sz, true);
err = validate_map_op(map, key_sz, value_sz, true, flags);
if (err)
return libbpf_err(err);
@@ -11020,7 +11034,7 @@ int bpf_map__get_next_key(const struct bpf_map *map,
{
int err;
err = validate_map_op(map, key_sz, 0, false /* check_value_sz */);
err = validate_map_op(map, key_sz, 0, false /* check_value_sz */, 0);
if (err)
return libbpf_err(err);

21
src/libbpf.h
View File

@@ -1216,12 +1216,13 @@ LIBBPF_API struct bpf_map *bpf_map__inner_map(struct bpf_map *map);
* @param key_sz size in bytes of key data, needs to match BPF map definition's **key_size**
* @param value pointer to memory in which looked up value will be stored
* @param value_sz size in byte of value data memory; it has to match BPF map
* definition's **value_size**. For per-CPU BPF maps value size has to be
* a product of BPF map value size and number of possible CPUs in the system
* (could be fetched with **libbpf_num_possible_cpus()**). Note also that for
* per-CPU values value size has to be aligned up to closest 8 bytes for
* alignment reasons, so expected size is: `round_up(value_size, 8)
* * libbpf_num_possible_cpus()`.
* definition's **value_size**. For per-CPU BPF maps, value size can be
* `value_size` if either **BPF_F_CPU** or **BPF_F_ALL_CPUS** is specified
* in **flags**, otherwise a product of BPF map value size and number of
* possible CPUs in the system (could be fetched with
* **libbpf_num_possible_cpus()**). Note also that for per-CPU values value
* size has to be aligned up to closest 8 bytes, so expected size is:
* `round_up(value_size, 8) * libbpf_num_possible_cpus()`.
* @param flags extra flags passed to kernel for this operation
* @return 0, on success; negative error, otherwise
*
@@ -1239,13 +1240,7 @@ LIBBPF_API int bpf_map__lookup_elem(const struct bpf_map *map,
* @param key pointer to memory containing bytes of the key
* @param key_sz size in bytes of key data, needs to match BPF map definition's **key_size**
* @param value pointer to memory containing bytes of the value
* @param value_sz size in byte of value data memory; it has to match BPF map
* definition's **value_size**. For per-CPU BPF maps value size has to be
* a product of BPF map value size and number of possible CPUs in the system
* (could be fetched with **libbpf_num_possible_cpus()**). Note also that for
* per-CPU values value size has to be aligned up to closest 8 bytes for
* alignment reasons, so expected size is: `round_up(value_size, 8)
* * libbpf_num_possible_cpus()`.
* @param value_sz refer to **bpf_map__lookup_elem**'s description.'
* @param flags extra flags passed to kernel for this operation
* @return 0, on success; negative error, otherwise
*