MIME-Version: 1.0
References: <20230123220500.21077-1-kirill.shutemov@linux.intel.com> <20230123220500.21077-6-kirill.shutemov@linux.intel.com>
In-Reply-To: <20230123220500.21077-6-kirill.shutemov@linux.intel.com>
From:   Alexander Potapenko <glider@google.com>
Date:   Thu, 9 Feb 2023 15:08:53 +0100
Message-ID: <CAG_fn=WuxXWfDRAnJdNu2i0_g6jFhhh27fHHUksb12bSW+53Sw@mail.gmail.com>
Subject: Re: [PATCHv15 05/17] mm: Introduce untagged_addr_remote()
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
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Mon, Jan 23, 2023 at 11:05 PM Kirill A. Shutemov
<kirill.shutemov@linux.intel.com> wrote:
>
> untagged_addr() removes tags/metadata from the address and brings it to
> the canonical form. The helper is implemented on arm64 and sparc. Both of
> them do untagging based on global rules.
>
> However, Linear Address Masking (LAM) on x86 introduces per-process
> settings for untagging. As a result, untagged_addr() is now only
> suitable for untagging addresses for the current proccess.
>
> The new helper untagged_addr_remote() has to be used when the address
> targets remote process. It requires the mmap lock for target mm to be
> taken.
>
> Export dump_mm() as there's now the first user for it: VFIO can be
> compiled as module and untagged_addr_remote() triggers dump_mm() via
> mmap_assert_locked().
>
> 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>