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

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Message-ID: <CAFULd4Z-q4Ot6iyOLo7DkjE=dY3RHXUV+yx6R0iWk=-tZ6ufhQ@mail.gmail.com>
Date:   Tue, 17 Oct 2023 23:05:52 +0200
From:   Uros Bizjak <ubizjak@...il.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Nadav Amit <namit@...are.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, Oct 17, 2023 at 9:11 PM Uros Bizjak <ubizjak@...il.com> wrote:
>
> On Tue, Oct 17, 2023 at 9:00 PM Linus Torvalds
> <torvalds@...ux-foundation.org> wrote:
> >
> > 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.
>
> Unfortunately, it doesn't fix the oops :(
>
> I'm testing your patch, together with the attached patch with the
> current tip tree (that already has all necessary percpu stuff), and
> get exactly the same oops in:

But adding the attached patch on top of both patches boots OK.

Uros.

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