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Date: Fri, 3 Sep 2021 08:28:02 +0200
From: "Gerd Hoffmann" <kraxel@redhat.com>
To: Brijesh Singh <brijesh.singh@amd.com>
Cc: devel@edk2.groups.io, James Bottomley <jejb@linux.ibm.com>,
	Min Xu <min.m.xu@intel.com>, Jiewen Yao <jiewen.yao@intel.com>,
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	Ard Biesheuvel <ardb+tianocore@kernel.org>,
	Erdem Aktas <erdemaktas@google.com>,
	Michael Roth <Michael.Roth@amd.com>
Subject: Re: [PATCH v6 02/29] OvmfPkg: reserve CPUID page for SEV-SNP
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  Hi,

> >> Is this snp-specific?  Or could this also be used without snp?
> > This is SNP specific format and cannot be used without SNP.
> 
> I should clarify the statement, the format itself does not contain
> anything  SNP specific. However, the CPUID page format is documented in
> the SNP specific spec.

Who populates the page?  qemu?  sev-snp firmware?

> Are you thinking about using it for non SEV guest
> to avoid the VM exit ? If so, it should be very much possible.

Yes, that is the background.  Avoiding vmexits would be one advantage.
Being able to test the code without SNP-capable hardware (for example
in CI) would be another one.

> For that
> we should define the format outside of SNP specific spec and make it a
> generic so that guest and HV's can implement it consume it in the
> non-SNP guest. 

I think that would be useful.

take care,
  Gerd