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References: <20230123220500.21077-1-kirill.shutemov@linux.intel.com> <20230123220500.21077-3-kirill.shutemov@linux.intel.com>
In-Reply-To: <20230123220500.21077-3-kirill.shutemov@linux.intel.com>
From:   Alexander Potapenko <glider@google.com>
Date:   Thu, 9 Feb 2023 15:06:56 +0100
Message-ID: <CAG_fn=Uozzi7xuA7KYYGg5qvKgnDOtdHrb7832XP2-3nky3_Cw@mail.gmail.com>
Subject: Re: [PATCHv15 02/17] x86: Allow atomic MM_CONTEXT flags setting
To:     "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc:     Dave Hansen <dave.hansen@linux.intel.com>,
        Andy Lutomirski <luto@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>, x86@kernel.org,
        Kostya Serebryany <kcc@google.com>,
        Andrey Ryabinin <ryabinin.a.a@gmail.com>,
        Andrey Konovalov <andreyknvl@gmail.com>,
        Taras Madan <tarasmadan@google.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        "H . J . Lu" <hjl.tools@gmail.com>,
        Andi Kleen <ak@linux.intel.com>,
        Rick Edgecombe <rick.p.edgecombe@intel.com>,
        Bharata B Rao <bharata@amd.com>,
        Jacob Pan <jacob.jun.pan@linux.intel.com>,
        Ashok Raj <ashok.raj@intel.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org
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On Mon, Jan 23, 2023 at 11:05 PM Kirill A. Shutemov
<kirill.shutemov@linux.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@linux.intel.com>
> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Alexander Potapenko <glider@google.com>