linux-kernel - Re: [tip: x86/mm] x86/mm: Use %RIP-relative address in untagged

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Message-ID: <CAFULd4Z3G0h_0vptZOJFy+gD7vd6296V7hvuHfNH1A7FroKNNw@mail.gmail.com>
Date:   Fri, 17 Nov 2023 17:40:25 +0100
From:   Uros Bizjak <ubizjak@...il.com>
To:     linux-kernel@...r.kernel.org
Cc:     linux-tip-commits@...r.kernel.org,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "Peter Zijlstra (Intel)" <peterz@...radaed.org>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        x86@...nel.org
Subject: Re: [tip: x86/mm] x86/mm: Use %RIP-relative address in untagged_addr()

On Fri, Nov 17, 2023 at 3:56 PM tip-bot2 for Uros Bizjak
<tip-bot2@...utronix.de> wrote:
>
> The following commit has been merged into the x86/mm branch of tip:
>
> Commit-ID:     bc5607d7777423b742f5b0f7a760d074154c613f
> Gitweb:        https://git.kernel.org/tip/bc5607d7777423b742f5b0f7a760d074154c613f
> Author:        Uros Bizjak <ubizjak@...il.com>
> AuthorDate:    Thu, 16 Nov 2023 20:10:59 +01:00
> Committer:     Dave Hansen <dave.hansen@...ux.intel.com>
> CommitterDate: Fri, 17 Nov 2023 06:27:29 -08:00
>
> x86/mm: Use %RIP-relative address in untagged_addr()
>
> %RIP-relative addresses are nowadays correctly handled in alternative
> instructions, so remove misleading comment and improve assembly to
> use %RIP-relative address.
>
> Also, explicitly using %gs: prefix will segfault for non-SMP builds.
> Use macros from percpu.h which will DTRT with segment prefix register
> as far as SMP/non-SMP builds are concerned.
>
> Signed-off-by: Uros Bizjak <ubizjak@...il.com>
> Signed-off-by: Dave Hansen <dave.hansen@...ux.intel.com>
> Acked-by: Peter Zijlstra (Intel) <peterz@...radaed.org>
> Acked-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> Link: https://lore.kernel.org/all/20231116191127.3446476-1-ubizjak%40gmail.com

I would just like to point out that this change depends on x86/percpu
branch in tip. So, the x86/mm has to come after x86/percpu.

Uros.