Commit 536b523b4073 for kernel

commit 536b523b407397c8d3967c020ce7aad70a0ea030
Author: Chen Pei <cp0613@linux.alibaba.com>
Date:   Wed Sep 2 14:14:51 2026 +0800

    bpf, riscv: Make arena support depend on ZACAS

    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() where it is defined, so arena map
    creation fails with -EOPNOTSUPP on systems without ZACAS. The macro
    is only defined when both CONFIG_RISCV_ISA_ZACAS and
    CONFIG_TOOLCHAIN_HAS_ZACAS are enabled, so guard it with #ifdef the
    same way mm/slab.h consumes it, and reject arena otherwise. 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")
    Signed-off-by: Chen Pei <cp0613@linux.alibaba.com>
    Acked-by: Pu Lehui <pulehui@huawei.com>
    Acked-by: Björn Töpel <bjorn@kernel.org>
    Cc: stable@vger.kernel.org
    Link: https://lore.kernel.org/bpf/20260902061451.1416-1-cp0613@linux.alibaba.com
    Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>

diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c
index 74efe4b138d2..151031e97a24 100644
--- a/arch/riscv/net/bpf_jit_comp64.c
+++ b/arch/riscv/net/bpf_jit_comp64.c
@@ -2128,7 +2128,15 @@ 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.
+	 */
+#ifdef system_has_cmpxchg128
+	return system_has_cmpxchg128();
+#else
+	return false;
+#endif
 }

 bool bpf_jit_supports_insn(struct bpf_insn *insn, bool in_arena)