[PATCH bpf-next v5 5/9] bpf: Add BPF_F_CPU and BPF_F_ALL_CPUS flags support for percpu_array maps

[Leon Hwang <leon.hwang@xxxxxxxxx>]

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

Introduce support for the BPF_F_CPU flag in percpu_array 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 of lookup_elem and update_elem APIs along with embedded cpu
  info.
* elem_flags of lookup_batch and update_batch APIs along with embedded
  cpu info.

Signed-off-by: Leon Hwang <leon.hwang@xxxxxxxxx>
---
 include/linux/bpf.h   |  7 ++++++-
 kernel/bpf/arraymap.c | 12 +++++++++---
 2 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index ef7f7c6a864c2..67122f852f16d 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -3754,7 +3754,12 @@ struct bpf_prog *bpf_prog_find_from_stack(void);
 
 static inline bool bpf_map_supports_cpu_flags(enum bpf_map_type map_type)
 {
-	return false;
+	switch (map_type) {
+	case BPF_MAP_TYPE_PERCPU_ARRAY:
+		return true;
+	default:
+		return false;
+	}
 }
 
 static inline int bpf_map_check_op_flags(struct bpf_map *map, u64 flags, u64 allowed_flags)
diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
index d02cce3202840..93acd4c93a3a8 100644
--- a/kernel/bpf/arraymap.c
+++ b/kernel/bpf/arraymap.c
@@ -301,6 +301,11 @@ int bpf_percpu_array_copy(struct bpf_map *map, void *key, void *value, u64 map_f
 	u32 index = *(u32 *)key;
 	void __percpu *pptr;
 	u32 size;
+	int err;
+
+	err = bpf_map_check_cpu_flags(map_flags, false);
+	if (unlikely(err))
+		return err;
 
 	if (unlikely(index >= array->map.max_entries))
 		return -ENOENT;
@@ -383,10 +388,11 @@ int bpf_percpu_array_update(struct bpf_map *map, void *key, void *value,
 	u32 index = *(u32 *)key;
 	void __percpu *pptr;
 	u32 size;
+	int err;
 
-	if (unlikely(map_flags > BPF_EXIST))
-		/* unknown flags */
-		return -EINVAL;
+	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 */
-- 
2.50.1