The arena range tree allocates its nodes with kmalloc_nolock() since commit f8c67d8550ee ("bpf: Use kmalloc_nolock() in range tree"). kmalloc_nolock() requires slab caches with cmpxchg128 support (__CMPXCHG_DOUBLE); on riscv cmpxchg128 is provided by the ZACAS extension. On systems without ZACAS every arena map creation fails with a misleading -ENOMEM. Report the missing support instead: make bpf_jit_supports_arena() return system_has_cmpxchg128(), so arena map creation fails with -EOPNOTSUPP on systems without ZACAS. This matches how arena BPF_CMPXCHG instructions are already gated on ZACAS in bpf_jit_supports_insn(). Fixes: f8c67d8550ee ("bpf: Use kmalloc_nolock() in range tree") Cc: stable@vger.kernel.org Signed-off-by: Chen Pei --- This issue was reported by sashiko-bot: https://sashiko.dev/#/patchset/20260901120013.16104-1-cp0613@linux.alibaba.com?part=1 Question for reviewers: should the arena selftests gate on ZACAS, e.g. probing it via riscv_hwprobe() (RISCV_ISA_EXT_ZACAS) and SKIPping cleanly on systems without the extension? arch/riscv/net/bpf_jit_comp64.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c index 74efe4b138d2..0061c1d4ed98 100644 --- a/arch/riscv/net/bpf_jit_comp64.c +++ b/arch/riscv/net/bpf_jit_comp64.c @@ -2128,7 +2128,11 @@ bool bpf_jit_supports_ptr_xchg(void) bool bpf_jit_supports_arena(void) { - return true; + /* + * The arena range tree uses kmalloc_nolock(), which needs + * cmpxchg128, provided by ZACAS on riscv. + */ + return system_has_cmpxchg128(); } bool bpf_jit_supports_insn(struct bpf_insn *insn, bool in_arena) -- 2.50.1