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

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Date:   Fri, 26 May 2017 13:04:39 +0800
From:   Xunlei Pang <xpang@...hat.com>
To:     Dave Young <dyoung@...hat.com>, Borislav Petkov <bp@...en8.de>
Cc:     linux-efi@...r.kernel.org, Brijesh Singh <brijesh.singh@....com>,
        Toshimitsu Kani <toshi.kani@....com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Matt Fleming <matt@...eblueprint.co.uk>, x86@...nel.org,
        linux-mm@...ck.org, Alexander Potapenko <glider@...gle.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Larry Woodman <lwoodman@...hat.com>,
        linux-arch@...r.kernel.org, kvm@...r.kernel.org,
        Jonathan Corbet <corbet@....net>,
        Joerg Roedel <joro@...tes.org>, linux-doc@...r.kernel.org,
        kasan-dev@...glegroups.com, Ingo Molnar <mingo@...hat.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Rik van Riel <riel@...hat.com>,
        Arnd Bergmann <arnd@...db.de>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        xlpang@...hat.com, Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Dmitry Vyukov <dvyukov@...gle.com>, kexec@...ts.infradead.org,
        linux-kernel@...r.kernel.org, iommu@...ts.linux-foundation.org,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: Re: [PATCH v5 31/32] x86: Add sysfs support for Secure Memory
 Encryption

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