linux-kernel - Re: [PATCH bpf-next 00/11] bpf: Mitigate Spectre v1 using barriers

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Message-ID: <87seneqq0o.fsf@fau.de>
Date: Sat, 15 Mar 2025 16:20:39 +0100
From: Luis Gerhorst <luis.gerhorst@....de>
To: Eduard Zingerman <eddyz87@...il.com>
Cc: Alexei Starovoitov <ast@...nel.org>,  Daniel Borkmann
 <daniel@...earbox.net>,  Andrii Nakryiko <andrii@...nel.org>,  Martin
 KaFai Lau <martin.lau@...ux.dev>,  Song Liu <song@...nel.org>,  Yonghong
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  Dimitar Kanaliev <dimitar.kanaliev@...eground.com>,  Shung-Hsi Yu
 <shung-hsi.yu@...e.com>,  Daniel Xu <dxu@...uu.xyz>,  bpf@...r.kernel.org,
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 Guo <guodongtai@...inos.cn>,  WANG Xuerui <git@...0n.name>,  Tiezhu Yang
 <yangtiezhu@...ngson.cn>
Subject: Re: [PATCH bpf-next 00/11] bpf: Mitigate Spectre v1 using barriers

Eduard Zingerman <eddyz87@...il.com> writes:
> I think it would be good to have some tests checking that nospec
> instructions are inserted in expected locations.
> Could you please take look at use of __xlated tag in e.g.
> tools/testing/selftests/bpf/progs/verifier_sdiv.c ?

That looks very promising, I will look into it for v2. Thanks for the
pointer.

I guess it might be worth it to add __xlated to at least on test per
nospec-related code path. If there are other rewrites at play that will
make it harder to adapt the tests when the other rewrite is ever
changed, but it might also help in catching interactions between the
other rewrites and the nospec.

Also, thanks for the review of patches 2 and 3.