Commit 2546863b authored by Leon Hwang's avatar Leon Hwang Committed by Alexei Starovoitov
Browse files

libbpf: Add BPF_F_CPU and BPF_F_ALL_CPUS flags support for percpu maps 



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: default avatarAndrii Nakryiko <andrii@kernel.org>
Signed-off-by: default avatarLeon Hwang <leon.hwang@linux.dev>
Link: https://lore.kernel.org/r/20260107022022.12843-7-leon.hwang@linux.dev


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 47c79f05

tools/lib/bpf/bpf.h

+8 −0
Original line number Diff line number Diff line
@@ -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

tools/lib/bpf/libbpf.c

+20 −6
Original line number Diff line number Diff line
@@ -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);

tools/lib/bpf/libbpf.h

+8 −13
Original line number Diff line number Diff line
@@ -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

 *