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Date: Thu, 17 Feb 2022 09:55:11 +0800 From: Hou Tao <houtao1@...wei.com> To: Will Deacon <will@...nel.org>, Daniel Borkmann <daniel@...earbox.net> CC: Alexei Starovoitov <ast@...nel.org>, Mark Rutland <mark.rutland@....com>, Martin KaFai Lau <kafai@...com>, Yonghong Song <yhs@...com>, Andrii Nakryiko <andrii@...nel.org>, Song Liu <songliubraving@...com>, "David S . Miller" <davem@...emloft.net>, John Fastabend <john.fastabend@...il.com>, <netdev@...r.kernel.org>, <bpf@...r.kernel.org>, Zi Shen Lim <zlim.lnx@...il.com>, Catalin Marinas <catalin.marinas@....com>, Julien Thierry <jthierry@...hat.com>, Ard Biesheuvel <ardb@...nel.org>, <linux-arm-kernel@...ts.infradead.org> Subject: Re: [PATCH bpf-next v3 2/4] arm64: insn: add encoders for atomic operations Hi, On 2/17/2022 1:16 AM, Will Deacon wrote: > On Fri, Feb 11, 2022 at 03:39:48PM +0100, Daniel Borkmann wrote: >> On 1/29/22 11:04 PM, Hou Tao wrote: >>> It is a preparation patch for eBPF atomic supports under arm64. eBPF >>> needs support atomic[64]_fetch_add, atomic[64]_[fetch_]{and,or,xor} and >>> atomic[64]_{xchg|cmpxchg}. The ordering semantics of eBPF atomics are >>> the same with the implementations in linux kernel. >>> >>> Add three helpers to support LDCLR/LDEOR/LDSET/SWP, CAS and DMB >>> instructions. STADD/STCLR/STEOR/STSET are simply encoded as aliases for >>> LDADD/LDCLR/LDEOR/LDSET with XZR as the destination register, so no extra >>> helper is added. atomic_fetch_add() and other atomic ops needs support for >>> STLXR instruction, so extend enum aarch64_insn_ldst_type to do that. >>> >>> LDADD/LDEOR/LDSET/SWP and CAS instructions are only available when LSE >>> atomics is enabled, so just return AARCH64_BREAK_FAULT directly in >>> these newly-added helpers if CONFIG_ARM64_LSE_ATOMICS is disabled. >>> >>> Signed-off-by: Hou Tao <houtao1@...wei.com> >> Hey Mark / Ard / Will / Catalin or others, could we get an Ack on patch 1 & 2 >> at min if it looks good to you? > I checked the instruction encodings in patches 1 and 2 and they all look > fine to me. However, after applying those two locally I get a build failure: > > | In file included from arch/arm64/net/bpf_jit_comp.c:23: > | arch/arm64/net/bpf_jit_comp.c: In function ‘build_insn’: > | arch/arm64/net/bpf_jit.h:94:2: error: implicit declaration of function ‘aarch64_insn_gen_stadd’; did you mean ‘aarch64_insn_gen_adr’? [-Werror=implicit-function-declaration] > | 94 | aarch64_insn_gen_stadd(Rn, Rs, A64_SIZE(sf)) > | | ^~~~~~~~~~~~~~~~~~~~~~ > | arch/arm64/net/bpf_jit_comp.c:912:9: note: in expansion of macro ‘A64_STADD’ > | 912 | emit(A64_STADD(isdw, reg, src), ctx); > | | ^~~~~~~~~ > | cc1: some warnings being treated as errors Thanks for your review. The build failure is my fault. I update A64_STADD() in patch 3 instead of patch 2 after replacing aarch64_insn_get_stadd() by aarch64_insn_gen_atomic_ld_op(), and will fix it in v4. If you are trying to test the encoder, I suggest you to apply patch 1~3. Regards, Tao > Will > .
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