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OvmfPkg: reserve CPUID page

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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.

Cc: Michael Roth <michael.roth@amd.com>
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: Min Xu <min.m.xu@intel.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Erdem Aktas <erdemaktas@google.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Acked-by: Jiewen Yao <Jiewen.yao@intel.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
This commit is contained in:
Brijesh Singh via groups.io
2021-12-09 11:27:34 +08:00
committed by mergify[bot]
parent 707c71a01b
commit cca9cd3dd6
5 changed files with 30 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
OvmfPkg/ResetVector/ResetVector.inf
View File

@@ -55,6 +55,8 @@
gUefiOvmfPkgTokenSpaceGuid.PcdBfvRawDataSize
[FixedPcd]
gUefiOvmfPkgTokenSpaceGuid.PcdOvmfCpuidBase
gUefiOvmfPkgTokenSpaceGuid.PcdOvmfCpuidSize
gUefiOvmfPkgTokenSpaceGuid.PcdSevLaunchSecretBase
gUefiOvmfPkgTokenSpaceGuid.PcdSevLaunchSecretSize
gUefiOvmfPkgTokenSpaceGuid.PcdQemuHashTableBase

2
OvmfPkg/ResetVector/ResetVector.nasmb
View File

@@ -105,6 +105,8 @@
%define SEV_ES_VC_TOP_OF_STACK (FixedPcdGet32 (PcdOvmfSecPeiTempRamBase) + FixedPcdGet32 (PcdOvmfSecPeiTempRamSize))
%define SEV_SNP_SECRETS_BASE (FixedPcdGet32 (PcdOvmfSnpSecretsBase))
%define SEV_SNP_SECRETS_SIZE (FixedPcdGet32 (PcdOvmfSnpSecretsSize))
%define CPUID_BASE (FixedPcdGet32 (PcdOvmfCpuidBase))
%define CPUID_SIZE (FixedPcdGet32 (PcdOvmfCpuidSize))
%include "X64/IntelTdxMetadata.asm"
%include "Ia32/Flat32ToFlat64.asm"

16
OvmfPkg/ResetVector/X64/OvmfSevMetadata.asm
View File

@@ -17,6 +17,16 @@ BITS 64
; AMD SEV-SNP specific sections
%define OVMF_SECTION_TYPE_SNP_SECRETS 0x2
;
; The section contains the hypervisor pre-populated CPUID values.
; In the case of SEV-SNP, the CPUID values are filtered and measured by
; the SEV-SNP firmware.
; The CPUID format is documented in SEV-SNP firmware spec 0.9 section 7.1
; (CPUID function structure).
;
%define OVMF_SECTION_TYPE_CPUID 0x3
ALIGN 16
TIMES (15 - ((OvmfSevGuidedStructureEnd - OvmfSevGuidedStructureStart + 15) % 16)) DB 0
@@ -39,5 +49,11 @@ SevSnpSecrets:
DD SEV_SNP_SECRETS_SIZE
DD OVMF_SECTION_TYPE_SNP_SECRETS
; CPUID values
CpuidSec:
DD CPUID_BASE
DD CPUID_SIZE
DD OVMF_SECTION_TYPE_CPUID
OvmfSevGuidedStructureEnd:
ALIGN 16