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

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Message-ID: <CAHk-=whTfDNK9bt24Ton_=Tw6pYYhr5FSei5Wx3MjDJKDcxGcA@mail.gmail.com>
Date:   Fri, 13 Oct 2023 09:38:38 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Uros Bizjak <ubizjak@...il.com>
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 Fri, 13 Oct 2023 at 04:53, Uros Bizjak <ubizjak@...il.com> wrote:
>
> Maybe we should go with what Clang expects. %a with "i" constraint is
> also what GCC handles, because
>
> ‘i’: An immediate integer operand (one with constant value) is
> allowed. This includes symbolic constants whose values will be known
> only at assembly time or later.

This looks fine to me, and would seem to be the simplest way to have
both gcc and clang be happy with things.

All these uses seem to be immediate addresses, as any actual dynamic
ones will use a proper "m" constraint (and no operand modifiers)

               Linus