linux-kernel - Re: [PATCHv15 02/17] x86: Allow atomic MM

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Date:   Thu, 9 Feb 2023 15:06:56 +0100
From:   Alexander Potapenko <glider@...gle.com>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc:     Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>, x86@...nel.org,
        Kostya Serebryany <kcc@...gle.com>,
        Andrey Ryabinin <ryabinin.a.a@...il.com>,
        Andrey Konovalov <andreyknvl@...il.com>,
        Taras Madan <tarasmadan@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        "H . J . Lu" <hjl.tools@...il.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Rick Edgecombe <rick.p.edgecombe@...el.com>,
        Bharata B Rao <bharata@....com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        Ashok Raj <ashok.raj@...el.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv15 02/17] x86: Allow atomic MM_CONTEXT flags setting

On Mon, Jan 23, 2023 at 11:05 PM Kirill A. Shutemov
<kirill.shutemov@...ux.intel.com> wrote:
>
> So far there's no need in atomic setting of MM context flags in
> mm_context_t::flags. The flags set early in exec and never change
> after that.
>
> LAM enabling requires atomic flag setting. The upcoming flag
> MM_CONTEXT_FORCE_TAGGED_SVA can be set much later in the process
> lifetime where multiple threads exist.
>
> Convert the field to unsigned long and do MM_CONTEXT_* accesses with
> __set_bit() and test_bit().
>
> No functional changes.
>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Tested-by: Alexander Potapenko <glider@...gle.com>