linux-kernel - Re: [RFC PATCH v2 04/20] x86: Secure Memory Encryption (SME) support

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Message-ID: <386eadac-b6eb-747e-65e7-1ffa4cfd7210@amd.com>
Date:   Wed, 31 Aug 2016 08:26:01 -0500
From:   Tom Lendacky <thomas.lendacky@....com>
To:     Andy Lutomirski <luto@...capital.net>
CC:     kasan-dev <kasan-dev@...glegroups.com>,
        "linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        <iommu@...ts.linux-foundation.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        Jonathan Corbet <corbet@....net>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        Alexander Potapenko <glider@...gle.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Arnd Bergmann <arnd@...db.de>, Joerg Roedel <joro@...tes.org>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        "H. Peter Anvin" <hpa@...or.com>, X86 ML <x86@...nel.org>,
        kvm list <kvm@...r.kernel.org>
Subject: Re: [RFC PATCH v2 04/20] x86: Secure Memory Encryption (SME) support

On 08/30/2016 09:57 AM, Andy Lutomirski wrote:
> On Aug 30, 2016 6:34 AM, "Tom Lendacky" <thomas.lendacky@....com> wrote:
>>
>> On 08/25/2016 08:04 AM, Thomas Gleixner wrote:
>>> On Mon, 22 Aug 2016, Tom Lendacky wrote:
>>>
>>>> Provide support for Secure Memory Encryption (SME). This initial support
>>>> defines the memory encryption mask as a variable for quick access and an
>>>> accessor for retrieving the number of physical addressing bits lost if
>>>> SME is enabled.
>>>
>>> What is the reason that this needs to live in assembly code?
>>
>> In later patches this code is expanded and deals with a lot of page
>> table manipulation, cpuid/rdmsr instructions, etc. and so I thought it
>> was best to do it this way.
> 
> None of that sounds like it needs to be in asm, though.
> 
> I, at least, have a strong preference for minimizing the amount of asm
> in the low-level arch code.

I can take a look at converting it over to C code.

Thanks,
Tom

> 
> --Andy
>