From mboxrd@z Thu Jan  1 00:00:00 1970
From: Xunlei Pang <xpang@redhat.com>
Subject: Re: [PATCH v5 31/32] x86: Add sysfs support for Secure Memory
 Encryption
Date: Fri, 26 May 2017 13:04:39 +0800
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Cc: linux-efi@vger.kernel.org, Brijesh Singh <brijesh.singh@amd.com>,
        Toshimitsu Kani <toshi.kani@hpe.com>,
        =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= <rkrcmar@redhat.com>,
        Matt Fleming <matt@codeblueprint.co.uk>, x86@kernel.org,
        linux-mm@kvack.org, 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>, linux-doc@vger.kernel.org,
        kasan-dev@googlegroups.com, Ingo Molnar <mingo@redhat.com>,
        Andrey Ryabinin <aryabinin@virtuozzo.com>,
        Tom Lendacky <thomas.lendacky@amd.com>,
        Rik van Riel <riel@redhat.com>,
        Arnd Bergmann <arnd@arndb.de>,
        Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
        xlpang@redhat.com, Andy
To: Dave Young <dyoung@redhat.com>, Borislav Petkov <bp@alien8.de>
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On 05/26/2017 at 10:49 AM, Dave Young wrote:
> Ccing Xunlei he is reading the patches see what need to be done for
> kdump. There should still be several places to handle to make kdump work.
>
> On 05/18/17 at 07:01pm, Borislav Petkov wrote:
>> On Tue, Apr 18, 2017 at 04:22:12PM -0500, Tom Lendacky wrote:
>>> Add sysfs support for SME so that user-space utilities (kdump, etc.) can
>>> determine if SME is active.
>> But why do user-space tools need to know that?
>>
>> I mean, when we load the kdump kernel, we do it with the first kernel,
>> with the kexec_load() syscall, AFAICT. And that code does a lot of
>> things during that init, like machine_kexec_prepare()->init_pgtable() to
>> prepare the ident mapping of the second kernel, for example.
>>
>> What I'm aiming at is that the first kernel knows *exactly* whether SME
>> is enabled or not and doesn't need to tell the second one through some
>> sysfs entries - it can do that during loading.
>>
>> So I don't think we need any userspace things at all...
> If kdump kernel can get the SME status from hardware register then this
> should be not necessary and this patch can be dropped.

Yes, I also agree with dropping this one.

Regards,
Xunlei