linux-kernel - Re: [PATCH v2 -tip] x86/percpu: Use C for arch_raw_cpu

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Message-ID: <CAHk-=wi7YKPKKZw5SpA9gZcf4paG4pZ2kUM50g-LQmdF0g6vWg@mail.gmail.com>
Date:   Tue, 17 Oct 2023 12:00:36 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Nadav Amit <namit@...are.com>
Cc:     Uros Bizjak <ubizjak@...il.com>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Brian Gerst <brgerst@...il.com>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>
Subject: Re: [PATCH v2 -tip] x86/percpu: Use C for arch_raw_cpu_ptr()

On Tue, 17 Oct 2023 at 00:23, Nadav Amit <namit@...are.com> wrote:
>
> Yes, the FPU issue is the one that caused me to crash before.

Uros, can you verify whether that patch of mine resolves the issue you saw?

That patch is _technically_ an actual bug-fix, although right now our
existing 'current' caching that depends on just CSE'ing the inline asm
(and is apparently limited to only doing so within single basic
blocks) doesn't actually trigger the bug in our __switch_to() logic in
practice.

            Linus