From: Daniel Borkmann <daniel@iogearbox.net>
To: WANG Xuerui <kernel@xen0n.name>, George Guo <guodongtai@kylinos.cn>
Cc: ast@kernel.org, bpf@vger.kernel.org, chenhuacai@kernel.org,
linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org,
loongarch@lists.linux.dev, masahiroy@kernel.org,
michal.lkml@markovi.net, ndesaulniers@google.com,
hengqi.chen@gmail.com, yangtiezhu@loongson.cn,
tangyouling@loongson.cn
Subject: Re: [PATCH v2] loongarch/bpf: Skip speculation barrier opcode, which caused ltp testcase bpf_prog02 to fail
Date: Tue, 28 Mar 2023 10:37:36 +0200 [thread overview]
Message-ID: <a8640220-4555-7f14-b1d3-deaaae587331@iogearbox.net> (raw)
In-Reply-To: <d4409486-7b3e-5b59-3b4e-9e832a7c98d5@xen0n.name>
On 3/28/23 9:52 AM, WANG Xuerui wrote:
> On 2023/3/28 15:22, Daniel Borkmann wrote:
>> On 3/28/23 9:13 AM, George Guo wrote:
>>> Here just skip the opcode(BPF_ST | BPF_NOSPEC) that has no couterpart to the loongarch.
>>>
>>> <snip>
>>>
>>> diff --git a/arch/loongarch/net/bpf_jit.c b/arch/loongarch/net/bpf_jit.c
>>> index 288003a9f0ca..d3c6b1c4ccbb 100644
>>> --- a/arch/loongarch/net/bpf_jit.c
>>> +++ b/arch/loongarch/net/bpf_jit.c
>>> @@ -1022,6 +1022,11 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx, bool ext
>>> emit_atomic(insn, ctx);
>>> break;
>>> + /* Speculation barrier */
>>> + case BPF_ST | BPF_NOSPEC:
>>> + pr_info_once("bpf_jit: skip speculation barrier opcode %0x2x\n", code);
>>> + break;
>>
>> Thanks that looks better. Question to LoongArch folks (Cc): There is no equivalent
>> to a speculation barrier here, correct? Either way, I think the pr_info_once() can
>> just be removed given there is little value for a users to have this in the kernel
>> log. I can take care of this while applying, that's fine.
>
> I can confirm there's currently no speculation barrier equivalent on lonogarch. (Loongson says there are builtin mitigations for Spectre-V1 and V2 on their chips, and AFAIK efforts to port the exploits to mips/loongarch have all failed a few years ago.)
>
> And yes I'd agree with removing the warning altogether. Thanks for the reviews!
>
> Acked-by: WANG Xuerui <git@xen0n.name>
Ok, sounds good. I've cleaned this up and applied to bpf tree. Thanks!
https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf.git/commit/?id=a6f6a95f25803500079513780d11a911ce551d76
prev parent reply other threads:[~2023-03-28 8:38 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-26 4:40 [PATCH] loongarch/bpf: Fix bpf load failed with CONFIG_BPF_JIT_ALWAYS_ON, caused by jit (BPF_ST | BPF_NOSPEC) code George Guo
2023-03-27 9:29 ` Daniel Borkmann
2023-03-28 7:13 ` [PATCH v2] loongarch/bpf: Skip speculation barrier opcode, which caused ltp testcase bpf_prog02 to fail George Guo
2023-03-28 7:22 ` Daniel Borkmann
2023-03-28 7:52 ` WANG Xuerui
2023-03-28 8:37 ` Daniel Borkmann [this message]
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