RE: [RFC 0/9] Linear Address Masking enabling

[Zhang, Xiang1]

There are already in llvm.org.
One of my old patch is https://reviews.llvm.org/D102472 which has been committed by https://reviews.llvm.org/D102901  and https://reviews.llvm.org/D109790

BR
Xiang

-----Original Message-----
From: H.J. Lu <hjl.tools@xxxxxxxxx> 
Sent: Wednesday, September 22, 2021 1:16 AM
To: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: Kirill A. Shutemov <kirill@xxxxxxxxxxxxx>; Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>; Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>; Lutomirski, Andy <luto@xxxxxxxxxx>; Peter Zijlstra <peterz@xxxxxxxxxxxxx>; the arch/x86 maintainers <x86@xxxxxxxxxx>; Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>; Alexander Potapenko <glider@xxxxxxxxxx>; Catalin Marinas <catalin.marinas@xxxxxxx>; Will Deacon <will@xxxxxxxxxx>; Andi Kleen <ak@xxxxxxxxxxxxxxx>; Linux-MM <linux-mm@xxxxxxxxx>; LKML <linux-kernel@xxxxxxxxxxxxxxx>; Carlos O'Donell <carlos@xxxxxxxxxx>; Marco Elver <elver@xxxxxxxxxx>; Taras Madan <tarasmadan@xxxxxxxxxx>; Zhang, Xiang1 <xiang1.zhang@xxxxxxxxx>
Subject: Re: [RFC 0/9] Linear Address Masking enabling

On Tue, Sep 21, 2021 at 9:52 AM Dmitry Vyukov <dvyukov@xxxxxxxxxx> wrote:
>
> On Sun, 7 Feb 2021 at 15:11, Kirill A. Shutemov <kirill@xxxxxxxxxxxxx> wrote:
> >
> > On Sun, Feb 07, 2021 at 09:24:23AM +0100, Dmitry Vyukov wrote:
> > > On Fri, Feb 5, 2021 at 4:16 PM Kirill A. Shutemov 
> > > <kirill.shutemov@xxxxxxxxxxxxxxx> 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 patchset brings support for LAM for userspace addresses.
> > > >
> > > > The most sensitive part of enabling is change in tlb.c, where 
> > > > CR3 flags get set. Please take a look that what I'm doing makes sense.
> > > >
> > > > The patchset is RFC quality and the code requires more testing 
> > > > before it can be applied.
> > > >
> > > > The userspace API is not finalized yet. The patchset extends API 
> > > > used by
> > > > ARM64: PR_GET/SET_TAGGED_ADDR_CTRL. The API is adjusted to not 
> > > > imply ARM
> > > > TBI: it now allows to request a number of bits of metadata 
> > > > needed and report where these bits are located in the address.
> > > >
> > > > There's an alternative proposal[2] for the API based on Intel 
> > > > CET interface. Please let us know if you prefer one over another.
> > > >
> > > > The feature competes for bits with 5-level paging: LAM_U48 makes 
> > > > it impossible to map anything about 47-bits. The patchset made 
> > > > these capability mutually exclusive: whatever used first wins. 
> > > > LAM_U57 can be combined with mappings above 47-bits.
> > > >
> > > > I include QEMU patch in case if somebody wants to play with the feature.
> > >
> > > Exciting! Do you plan to send the QEMU patch to QEMU?
> >
> > Sure. After more testing, once I'm sure it's conforming to the hardware.
>
> A follow up after H.J.'s LPC talk:
> https://linuxplumbersconf.org/event/11/contributions/1010/
> (also +Carlos)
>
> As far as I understood, this kernel series depends on the Intel CET patches.
>
> Where are these compiler-rt patches that block gcc support?

Hi Xiang,

Please share your compiler-rt changes for LAM.

--
H.J.