linux-kernel - Re: [RFC PATCH v2 12/32] x86: Add early boot support when running with SEV active

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Date:   Thu, 16 Mar 2017 11:16:56 +0100
From:   Borislav Petkov <bp@...e.de>
To:     Brijesh Singh <brijesh.singh@....com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>, simon.guinot@...uanux.org,
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Subject: Re: [RFC PATCH v2 12/32] x86: Add early boot support when running
 with SEV active

On Fri, Mar 10, 2017 at 10:35:30AM -0600, Brijesh Singh wrote:
> We could update this patch to use the below logic:
> 
>  * CPUID(0) - Check for AuthenticAMD
>  * CPID(1) - Check if under hypervisor
>  * CPUID(0x80000000) - Check for highest supported leaf
>  * CPUID(0x8000001F).EAX - Check for SME and SEV support
>  * rdmsr (MSR_K8_SYSCFG)[MemEncryptionModeEnc] - Check if SMEE is set

Actually, it is still not clear to me *why* we need to do anything
special wrt SEV in the guest.

Lemme clarify: why can't the guest boot just like a normal Linux on
baremetal and use the SME(!) detection code to set sme_enable and so
on? IOW, I'd like to avoid all those checks whether we're running under
hypervisor and handle all that like we're running on baremetal.

-- 
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
--