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

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Date:   Tue, 18 Oct 2022 13:07:29 -0700
From:   Ashok Raj <ashok.raj@...el.com>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.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>,
        Ashok Raj <ashok.raj@...el.com>
Subject: Re: [PATCHv10 10/15] x86/mm, iommu/sva: Make LAM and SVM mutually
 exclusive

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>

> 
> 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 :-)

Cheers,
Ashok