Feedback-ID: ie3994620:Fastmail
Date:   Tue, 24 Jan 2023 14:01:58 +0300
From:   "Kirill A. Shutemov" <kirill@shutemov.name>
To:     Linus Torvalds <torvalds@linux-foundation.org>
Cc:     "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        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>,
        Alexander Potapenko <glider@google.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>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCHv15 00/17] Linear Address Masking enabling
Message-ID: <20230124110158.bwqu3v2evoa3ffw6@box.shutemov.name>
References: <20230123220500.21077-1-kirill.shutemov@linux.intel.com>
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On Mon, Jan 23, 2023 at 06:07:20PM -0800, Linus Torvalds wrote:
> On Mon, Jan 23, 2023 at 2:05 PM Kirill A. Shutemov
> <kirill.shutemov@linux.intel.com> wrote:
> >
> > Linear Address Masking[1] (LAM) modifies the checking that is applied to
> > 64-bit linear addresses, allowing software to use of the untranslated
> > address bits for metadata.
> >
> > The capability can be used for efficient address sanitizers (ASAN)
> > implementation and for optimizations in JITs and virtual machines.
> >
> > The patchset brings support for LAM for userspace addresses. Only LAM_U57 at
> > this time.
> 
> I didn't react to anything objectionable in the series.
> 
> My only reaction was actually to ask "when / what CPU cores are
> expected to support this feature"?
> 
> Maybe it was mentioned somewhere, and I'm just blind and not finding
> it.  But even the "Instruction Set Extensions and Future Features"
> paper seems to just be talking about the CPUID bits, not about any
> actual "this is when we expect it".

There's no announced CPUs that have the feature. And it is above my pay
grade to disclose anything beyond that.

But there's QEMU patch[1] if you want to play with the feature. The patch
is not upstreamable, but it works.

[1] https://lore.kernel.org/qemu-devel/20220407010107.34734-1-kirill.shutemov@linux.intel.com/

-- 
  Kiryl Shutsemau / Kirill A. Shutemov