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 for kexec@lists.infradead.org; Thu, 04 May 2017 14:14:06 +0000
Subject: Re: [PATCH v5 31/32] x86: Add sysfs support for Secure Memory
 Encryption
References: <20170418211612.10190.82788.stgit@tlendack-t1.amdoffice.net>
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From: Tom Lendacky <thomas.lendacky@amd.com>
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Date: Thu, 4 May 2017 09:13:35 -0500
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To: Dave Young <dyoung@redhat.com>, Dave Hansen <dave.hansen@intel.com>
Cc: linux-efi@vger.kernel.org, Brijesh Singh <brijesh.singh@amd.com>, Toshimitsu Kani <toshi.kani@hpe.com>, linux-doc@vger.kernel.org, Matt Fleming <matt@codeblueprint.co.uk>, linux-mm@kvack.org, =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= <rkrcmar@redhat.com>, Alexander Potapenko <glider@google.com>, "H. Peter
 Anvin" <hpa@zytor.com>, Larry Woodman <lwoodman@redhat.com>, linux-arch@vger.kernel.org, kvm@vger.kernel.org, Jonathan Corbet <corbet@lwn.net>, Joerg Roedel <joro@8bytes.org>, x86@kernel.org, kasan-dev@googlegroups.com, Ingo Molnar <mingo@redhat.com>, Andrey Ryabinin <aryabinin@virtuozzo.com>, Rik van Riel <riel@redhat.com>, Arnd Bergmann <arnd@arndb.de>, Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>, Borislav Petkov <bp@alien8.de>, Andy Lutomirski <luto@kernel.org>, Thomas Gleixner <tglx@linutronix.de>, Dmitry Vyukov <dvyukov@google.com>, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, "Michael S.
 Tsirkin" <mst@redhat.com>, Paolo Bonzini <pbonzini@redhat.com>

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
>

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