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| author | Daniel Borkmann <daniel@iogearbox.net> | 2019-04-26 21:48:21 +0200 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2019-04-26 18:53:15 -0700 |
| commit | 8968c67a82ab7501bc3b9439c3624a49b42fe54c (patch) | |
| tree | b377d4184b0c45b275e6548e163961ece6443539 | |
| parent | 0c0cad2c2824ac38106ad0649263eca30954beb6 (diff) | |
| download | linux-8968c67a82ab7501bc3b9439c3624a49b42fe54c.tar.gz linux-8968c67a82ab7501bc3b9439c3624a49b42fe54c.tar.bz2 linux-8968c67a82ab7501bc3b9439c3624a49b42fe54c.zip | |
bpf, arm64: remove prefetch insn in xadd mapping
Prefetch-with-intent-to-write is currently part of the XADD mapping in
the AArch64 JIT and follows the kernel's implementation of atomic_add.
This may interfere with other threads executing the LDXR/STXR loop,
leading to potential starvation and fairness issues. Drop the optional
prefetch instruction.
Fixes: 85f68fe89832 ("bpf, arm64: implement jiting of BPF_XADD")
Reported-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Jean-Philippe Brucker <jean-philippe.brucker@arm.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
| -rw-r--r-- | arch/arm64/net/bpf_jit.h | 6 | ||||
| -rw-r--r-- | arch/arm64/net/bpf_jit_comp.c | 1 |
2 files changed, 0 insertions, 7 deletions
diff --git a/arch/arm64/net/bpf_jit.h b/arch/arm64/net/bpf_jit.h index 783de51a6c4e..6c881659ee8a 100644 --- a/arch/arm64/net/bpf_jit.h +++ b/arch/arm64/net/bpf_jit.h @@ -100,12 +100,6 @@ #define A64_STXR(sf, Rt, Rn, Rs) \ A64_LSX(sf, Rt, Rn, Rs, STORE_EX) -/* Prefetch */ -#define A64_PRFM(Rn, type, target, policy) \ - aarch64_insn_gen_prefetch(Rn, AARCH64_INSN_PRFM_TYPE_##type, \ - AARCH64_INSN_PRFM_TARGET_##target, \ - AARCH64_INSN_PRFM_POLICY_##policy) - /* Add/subtract (immediate) */ #define A64_ADDSUB_IMM(sf, Rd, Rn, imm12, type) \ aarch64_insn_gen_add_sub_imm(Rd, Rn, imm12, \ diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c index aaddc0217e73..a1420626fca2 100644 --- a/arch/arm64/net/bpf_jit_comp.c +++ b/arch/arm64/net/bpf_jit_comp.c @@ -762,7 +762,6 @@ emit_cond_jmp: case BPF_STX | BPF_XADD | BPF_DW: emit_a64_mov_i(1, tmp, off, ctx); emit(A64_ADD(1, tmp, tmp, dst), ctx); - emit(A64_PRFM(tmp, PST, L1, STRM), ctx); emit(A64_LDXR(isdw, tmp2, tmp), ctx); emit(A64_ADD(isdw, tmp2, tmp2, src), ctx); emit(A64_STXR(isdw, tmp2, tmp, tmp3), ctx); |