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Date: Thu, 2 Sep 2021 10:04:48 +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>,
	Tom Lendacky <thomas.lendacky@amd.com>,
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	Ard Biesheuvel <ardb+tianocore@kernel.org>,
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Subject: Re: [PATCH v6 02/29] OvmfPkg: reserve CPUID page for SEV-SNP
Message-ID: <20210902080448.jjigp62hsfo4o2h6@sirius.home.kraxel.org>
References: <20210901161646.24763-1-brijesh.singh@amd.com>
 <20210901161646.24763-3-brijesh.singh@amd.com>
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On Wed, Sep 01, 2021 at 11:16:19AM -0500, Brijesh Singh wrote:
> BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3275
> 
> Platform features and capabilities are traditionally discovered via the
> CPUID instruction. Hypervisors typically trap and emulate the CPUID
> instruction for a variety of reasons. There are some cases where incorrect
> CPUID information can potentially lead to a security issue. The SEV-SNP
> firmware provides a feature to filter the CPUID results through the PSP.
> The filtered CPUID values are saved on a special page for the guest to
> consume. Reserve a page in MEMFD that will contain the results of
> filtered CPUID values.

Is the format of the page documented somewhere?
Is this snp-specific?  Or could this also be used without snp?

thanks,
  Gerd