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

Tom Lendacky
2017-05-26T15:49:16Z

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
>