[PATCH bpf-next v2] bpf: hardcode BPF_PROG_PACK_SIZE to 2MB * num_possible_nodes()

[Puranjay Mohan]

On some architectures like ARM64, PMD_SIZE can be really large in some
configurations. Like with CONFIG_ARM64_64K_PAGES=y the PMD_SIZE is
512MB.

Use 2MB * num_possible_nodes() as the size for allocations done through
the prog pack allocator. On most architectures, PMD_SIZE will be equal
to 2MB in case of 4KB pages and will be greater than 2MB for bigger page
sizes.

Fixes: ea2babac63d4 ("bpf: Simplify bpf_prog_pack_[size|mask]")
Reported-by: "kernelci.org bot" <bot@xxxxxxxxxxxx>
Closes: https://lore.kernel.org/all/7e216c88-77ee-47b8-becc-a0f780868d3c@xxxxxxxxxxxxx/
Reported-by: kernel test robot <lkp@xxxxxxxxx>
Closes: https://lore.kernel.org/oe-kbuild-all/202403092219.dhgcuz2G-lkp@xxxxxxxxx/
Suggested-by: Song Liu <song@xxxxxxxxxx>
Signed-off-by: Puranjay Mohan <puranjay12@xxxxxxxxx>
---
 kernel/bpf/core.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 134b7979f537..a8007f7f706d 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -893,7 +893,12 @@ static LIST_HEAD(pack_list);
  * CONFIG_MMU=n. Use PAGE_SIZE in these cases.
  */
 #ifdef PMD_SIZE
-#define BPF_PROG_PACK_SIZE (PMD_SIZE * num_possible_nodes())
+/* PMD_SIZE is really big for some archs. It doesn't make sense to
+ * reserve too much memory in one allocation. Hardcode BPF_PROG_PACK_SIZE to
+ * 2MiB * num_possible_nodes(). On most architectures PMD_SIZE will be
+ * greater than or equal to 2MB.
+ */
+#define BPF_PROG_PACK_SIZE (SZ_2M * num_possible_nodes())
 #else
 #define BPF_PROG_PACK_SIZE PAGE_SIZE
 #endif
-- 
2.40.1