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

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Date:   Fri, 26 May 2017 10:47:39 -0500
From:   Tom Lendacky <thomas.lendacky@....com>
To:     <xlpang@...hat.com>, 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>,
        Rik van Riel <riel@...hat.com>,
        Arnd Bergmann <arnd@...db.de>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.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 5/26/2017 12:04 AM, Xunlei Pang wrote:
> 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.

Consensus is to drop, so it will be.

Thanks,
Tom

>
> Regards,
> Xunlei
>