linux-kernel - Re: [PATCHv10 10/15] x86/mm, iommu/sva: Make LAM and SVM mutually exclusive

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Message-ID: <20221018223537.7bmhuknclkboqgnk@box.shutemov.name>
Date:   Wed, 19 Oct 2022 01:35:37 +0300
From:   "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:     Ashok Raj <ashok.raj@...el.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>,
        Alexander Potapenko <glider@...gle.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>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCHv10 10/15] x86/mm, iommu/sva: Make LAM and SVM mutually
 exclusive

On Tue, Oct 18, 2022 at 01:07:29PM -0700, Ashok Raj wrote:
> On Tue, Oct 18, 2022 at 02:33:53PM +0300, Kirill A. Shutemov wrote:
> > IOMMU and SVM-capable devices know nothing about LAM and only expect
> > canonical addresses. Attempt to pass down tagged pointer will lead to
> > address translation failure.
> > 
> > By default do not allow to enable both LAM and use SVM in the same
> > process.
> > 
> > The new ARCH_FORCE_TAGGED_SVM arch_prctl() overrides the limitation.
> > By using the arch_prctl() userspace takes responsibility to never pass
> > tagged address to the device.
> 
> Reviewed-by: Ashok Raj <ashok.raj@...el.com>

Thanks!

> > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> > ---
> >  arch/x86/include/asm/mmu.h         |  6 ++++--
> >  arch/x86/include/asm/mmu_context.h |  2 ++
> >  arch/x86/include/uapi/asm/prctl.h  |  1 +
> >  arch/x86/kernel/process_64.c       | 13 +++++++++++++
> >  drivers/iommu/iommu-sva-lib.c      | 12 ++++++++++++
> >  include/linux/mmu_context.h        |  4 ++++
> >  6 files changed, 36 insertions(+), 2 deletions(-)
> > 
> > diff --git a/arch/x86/include/asm/mmu.h b/arch/x86/include/asm/mmu.h
> > index 2fdb390040b5..cce9b32b0d6d 100644
> > --- a/arch/x86/include/asm/mmu.h
> > +++ b/arch/x86/include/asm/mmu.h
> > @@ -9,9 +9,11 @@
> >  #include <linux/bits.h>
> >  
> >  /* Uprobes on this MM assume 32-bit code */
> > -#define MM_CONTEXT_UPROBE_IA32	BIT(0)
> > +#define MM_CONTEXT_UPROBE_IA32		BIT(0)
> >  /* vsyscall page is accessible on this MM */
> > -#define MM_CONTEXT_HAS_VSYSCALL	BIT(1)
> > +#define MM_CONTEXT_HAS_VSYSCALL		BIT(1)
> 
> Nit: Looks like the two above format changes got in here :-)

That's side effect of keeping the new longer flag aligned to the rest.

A separate patch looks like an overkill, no?

-- 
  Kiryl Shutsemau / Kirill A. Shutemov