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.

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    Boris.

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