linux-kernel - Re: [RFC PATCH v4 03/28] x86: Add the Secure Memory Encryption CPU feature

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Date:   Thu, 16 Feb 2017 21:06:08 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Tom Lendacky <thomas.lendacky@....com>
Cc:     linux-arch@...r.kernel.org, linux-efi@...r.kernel.org,
        kvm@...r.kernel.org, linux-doc@...r.kernel.org, x86@...nel.org,
        linux-kernel@...r.kernel.org, kasan-dev@...glegroups.com,
        linux-mm@...ck.org, iommu@...ts.linux-foundation.org,
        Rik van Riel <riel@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Toshimitsu Kani <toshi.kani@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Jonathan Corbet <corbet@....net>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Joerg Roedel <joro@...tes.org>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Brijesh Singh <brijesh.singh@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Alexander Potapenko <glider@...gle.com>,
        Andy Lutomirski <luto@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Larry Woodman <lwoodman@...hat.com>,
        Dmitry Vyukov <dvyukov@...gle.com>
Subject: Re: [RFC PATCH v4 03/28] x86: Add the Secure Memory Encryption CPU
 feature

On Thu, Feb 16, 2017 at 01:42:13PM -0600, Tom Lendacky wrote:
> I realize it's a bit more code and expands the changes but I thought it
> would be a bit clearer as to what was going on this way. And then the
> follow on patch for the physical address reduction goes in nicely, too.

Well, the code from the next patch should go to AMD-specific place like
arch/x86/kernel/cpu/amd.c anyway, where you don't have to do vendor
checks.

> If you prefer I stay with the scattered feature approach and then clear
> the bit based on the MSR at the end of init_amd() I can do that. I'm
> not attached to either method.

Yes please. We should keep the shole X86_FEATURE machinery from
exploding in size. Especially if CPUID_0x8000001f is not a leaf we're
going to be adding the majority of its bits, to warrant a separate
->x86_capability array element.

  [If it does later, we can always move it to a separate element. ]

Thanks.

-- 
Regards/Gruss,
    Boris.

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