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When launching a SEV-SNP VM, the ROM is not all that must be measured. The OvmfSevMetadata sections describe ranges of memory that must be measured with different types than PAGE_TYPE_NORMAL, except one. The SevSnpKernelHashes page is also PAGE_TYPE_NORMAL, but is populated by the VMM from configuration data that is separate from the OVMF build itself. To more compactly provide reference values for the measurement of the firmware separately from the kernel hashes, it's advantageous to measure as much known information as possible first. Whereas VMMs are permitted to measure these sections in any order they prefer, the normative order of how they appear in the .fd is easiest to follow. This change is semantics-preserving. Measurement calculation tools that do not follow the normative ordering would need updating to accommodate, but I don't know of any. The accounting for EC2 moving the CPUID page to the end of measurement would be unchanged. This change is to improve performance of a proposed launch update event log to separate responsibility for initially measured data before VM launch, application/vnd.amd.sevsnp.launch-updates+cbor: https://github.com/deeglaze/draft-deeglaze-amd-sev-snp-corim-profile Signed-off-by: Dionna Glaze <dionnaglaze@google.com>
96 lines
2.7 KiB
NASM
96 lines
2.7 KiB
NASM
;-----------------------------------------------------------------------------
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; @file
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; OVMF metadata for the AMD SEV confidential computing guests
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;
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; Copyright (c) 2021 - 2024, AMD Inc. All rights reserved.<BR>
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;
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; SPDX-License-Identifier: BSD-2-Clause-Patent
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;-----------------------------------------------------------------------------
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BITS 64
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%define OVMF_SEV_METADATA_VERSION 1
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; The section must be accepted or validated by the VMM before the boot
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%define OVMF_SECTION_TYPE_SNP_SEC_MEM 0x1
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; AMD SEV-SNP specific sections
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%define OVMF_SECTION_TYPE_SNP_SECRETS 0x2
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;
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; The section contains the hypervisor pre-populated CPUID values.
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; In the case of SEV-SNP, the CPUID values are filtered and measured by
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; the SEV-SNP firmware.
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; The CPUID format is documented in SEV-SNP firmware spec 0.9 section 7.1
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; (CPUID function structure).
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;
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%define OVMF_SECTION_TYPE_CPUID 0x3
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; The SVSM Calling Area Address (CAA)
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%define OVMF_SECTION_TYPE_SVSM_CAA 0x4
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; Kernel hashes section for measured direct boot
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%define OVMF_SECTION_TYPE_KERNEL_HASHES 0x10
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ALIGN 16
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TIMES (15 - ((OvmfSevGuidedStructureEnd - OvmfSevGuidedStructureStart + 15) % 16)) DB 0
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OvmfSevGuidedStructureStart:
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;
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; OvmfSev metadata descriptor
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;
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OvmfSevMetadataGuid:
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_DescriptorSev:
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DB 'A','S','E','V' ; Signature
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DD OvmfSevGuidedStructureEnd - _DescriptorSev ; Length
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DD OVMF_SEV_METADATA_VERSION ; Version
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DD (OvmfSevGuidedStructureEnd - _DescriptorSev - 16) / 12 ; Number of sections
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; Region need to be pre-validated by the hypervisor
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PreValidate1:
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DD SNP_SEC_MEM_BASE_DESC_1
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DD SNP_SEC_MEM_SIZE_DESC_1
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DD OVMF_SECTION_TYPE_SNP_SEC_MEM
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PreValidate2:
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DD SNP_SEC_MEM_BASE_DESC_2
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DD SNP_SEC_MEM_SIZE_DESC_2
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DD OVMF_SECTION_TYPE_SNP_SEC_MEM
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; SEV-SNP Secrets page
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SevSnpSecrets:
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DD SEV_SNP_SECRETS_BASE
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DD SEV_SNP_SECRETS_SIZE
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DD OVMF_SECTION_TYPE_SNP_SECRETS
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; CPUID values
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CpuidSec:
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DD CPUID_BASE
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DD CPUID_SIZE
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DD OVMF_SECTION_TYPE_CPUID
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; SVSM CAA page
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SvsmCaa:
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DD SVSM_CAA_BASE
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DD SVSM_CAA_SIZE
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DD OVMF_SECTION_TYPE_SVSM_CAA
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; Region need to be pre-validated by the hypervisor
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PreValidate3:
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DD SNP_SEC_MEM_BASE_DESC_3
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DD SNP_SEC_MEM_SIZE_DESC_3
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DD OVMF_SECTION_TYPE_SNP_SEC_MEM
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%if (SEV_SNP_KERNEL_HASHES_BASE > 0)
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; Kernel hashes for measured direct boot, or zero page if
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; there are no kernel hashes / SEV secrets
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SevSnpKernelHashes:
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DD SEV_SNP_KERNEL_HASHES_BASE
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DD SEV_SNP_KERNEL_HASHES_SIZE
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DD OVMF_SECTION_TYPE_KERNEL_HASHES
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%endif
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OvmfSevGuidedStructureEnd:
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ALIGN 16
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