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

Xunlei Pang
2017-05-26T05:03:21Z

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