linux-kernel - Re: [PATCH v5 31/32] x86: Add sysfs support for Secure Memory Encryption

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Message-ID: <2abc7ad8-9d64-8617-44fe-1cb8af31e1f6@amd.com>
Date:   Thu, 4 May 2017 09:13:35 -0500
From:   Tom Lendacky <thomas.lendacky@....com>
To:     Dave Young <dyoung@...hat.com>, Dave Hansen <dave.hansen@...el.com>
CC:     <linux-arch@...r.kernel.org>, <linux-efi@...r.kernel.org>,
        <kvm@...r.kernel.org>, <linux-doc@...r.kernel.org>,
        <x86@...nel.org>, <kexec@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <kasan-dev@...glegroups.com>,
        <linux-mm@...ck.org>, <iommu@...ts.linux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Rik van Riel <riel@...hat.com>,
        Brijesh Singh <brijesh.singh@....com>,
        Toshimitsu Kani <toshi.kani@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Jonathan Corbet <corbet@....net>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        Joerg Roedel <joro@...tes.org>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Ingo Molnar <mingo@...hat.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Andy Lutomirski <luto@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...en8.de>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Alexander Potapenko <glider@...gle.com>,
        Larry Woodman <lwoodman@...hat.com>,
        Dmitry Vyukov <dvyukov@...gle.com>
Subject: Re: [PATCH v5 31/32] x86: Add sysfs support for Secure Memory
 Encryption

On 4/27/2017 2:25 AM, Dave Young wrote:
> On 04/21/17 at 02:55pm, Dave Hansen wrote:
>> On 04/18/2017 02:22 PM, Tom Lendacky wrote:
>>> Add sysfs support for SME so that user-space utilities (kdump, etc.) can
>>> determine if SME is active.
>>>
>>> A new directory will be created:
>>>   /sys/kernel/mm/sme/
>>>
>>> And two entries within the new directory:
>>>   /sys/kernel/mm/sme/active
>>>   /sys/kernel/mm/sme/encryption_mask
>>
>> Why do they care, and what will they be doing with this information?
>
> Since kdump will copy old memory but need this to know if the old memory
> was encrypted or not. With this sysfs file we can know the previous SME
> status and pass to kdump kernel as like a kernel param.
>
> Tom, have you got chance to try if it works or not?

Sorry, I haven't had a chance to test this yet.

Thanks,
Tom

>
> Thanks
> Dave
>