[edk2-devel] [PATCH v13 04/32] OvmfPkg/ResetVector: introduce SEV metadata descriptor for VMM use

[Brijesh Singh via groups.io]

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3275

The OvmfPkgX86 build reserves memory regions in MEMFD. The memory regions
get accessed in the SEC phase. AMD SEV-SNP require that the guest's
private memory be accepted or validated before access.

Introduce a Guided metadata structure that describes the reserved memory
regions. The VMM can locate the metadata structure by iterating through
the reset vector guid and process the areas based on the platform
specific requirements.

Cc: Michael Roth <michael.roth at amd.com>
Cc: James Bottomley <jejb at linux.ibm.com>
Cc: Min Xu <min.m.xu at intel.com>
Cc: Jiewen Yao <jiewen.yao at intel.com>
Cc: Tom Lendacky <thomas.lendacky at amd.com>
Cc: Jordan Justen <jordan.l.justen at intel.com>
Cc: Ard Biesheuvel <ardb+tianocore at kernel.org>
Cc: Erdem Aktas <erdemaktas at google.com>
Cc: Gerd Hoffmann <kraxel at redhat.com>
Acked-by: Gerd Hoffmann <kraxel at redhat.com>
Signed-off-by: Brijesh Singh <brijesh.singh at amd.com>
---
 OvmfPkg/ResetVector/Ia16/ResetVectorVtf0.asm | 14 ++++++++
 OvmfPkg/ResetVector/ResetVector.nasmb        |  1 +
 OvmfPkg/ResetVector/X64/OvmfSevMetadata.asm  | 34 ++++++++++++++++++++
 3 files changed, 49 insertions(+)
 create mode 100644 OvmfPkg/ResetVector/X64/OvmfSevMetadata.asm

diff --git a/OvmfPkg/ResetVector/Ia16/ResetVectorVtf0.asm b/OvmfPkg/ResetVector/Ia16/ResetVectorVtf0.asm
index dee2e3f9de31..12f2cedd6767 100644
--- a/OvmfPkg/ResetVector/Ia16/ResetVectorVtf0.asm
+++ b/OvmfPkg/ResetVector/Ia16/ResetVectorVtf0.asm
@@ -64,6 +64,20 @@ tdxMetadataOffsetStart:
     DB      0x86, 0x5e, 0x46, 0x85, 0xa7, 0xbf, 0x8e, 0xc2
 tdxMetadataOffsetEnd:
 
+;
+; SEV metadata descriptor
+;
+; Provide the start offset of the metadata blob within the OVMF binary.
+
+; GUID : dc886566-984a-4798-A75e-5585a7bf67cc
+;
+OvmfSevMetadataOffsetStart:
+  DD      (fourGigabytes - OvmfSevMetadataGuid)
+  DW      OvmfSevMetadataOffsetEnd - OvmfSevMetadataOffsetStart
+  DB      0x66, 0x65, 0x88, 0xdc, 0x4a, 0x98, 0x98, 0x47
+  DB      0xA7, 0x5e, 0x55, 0x85, 0xa7, 0xbf, 0x67, 0xcc
+OvmfSevMetadataOffsetEnd:
+
 %endif
 
 ; SEV Hash Table Block
diff --git a/OvmfPkg/ResetVector/ResetVector.nasmb b/OvmfPkg/ResetVector/ResetVector.nasmb
index 87effedb9c60..d847794feadb 100644
--- a/OvmfPkg/ResetVector/ResetVector.nasmb
+++ b/OvmfPkg/ResetVector/ResetVector.nasmb
@@ -109,6 +109,7 @@
 %include "Ia32/AmdSev.asm"
 %include "Ia32/PageTables64.asm"
 %include "Ia32/IntelTdx.asm"
+%include "X64/OvmfSevMetadata.asm"
 %endif
 
 %include "Ia16/Real16ToFlat32.asm"
diff --git a/OvmfPkg/ResetVector/X64/OvmfSevMetadata.asm b/OvmfPkg/ResetVector/X64/OvmfSevMetadata.asm
new file mode 100644
index 000000000000..9d8c3e8194a4
--- /dev/null
+++ b/OvmfPkg/ResetVector/X64/OvmfSevMetadata.asm
@@ -0,0 +1,34 @@
+;-----------------------------------------------------------------------------
+; @file
+; OVMF metadata for the AMD SEV confidential computing guests
+;
+; Copyright (c) 2021, AMD Inc. All rights reserved.<BR>
+;
+; SPDX-License-Identifier: BSD-2-Clause-Patent
+;-----------------------------------------------------------------------------
+
+BITS  64
+
+%define OVMF_SEV_METADATA_VERSION     1
+
+; The section must be accepted or validated by the VMM before the boot
+%define OVMF_SECTION_TYPE_SNP_SEC_MEM     0x1
+
+ALIGN 16
+
+TIMES (15 - ((OvmfSevGuidedStructureEnd - OvmfSevGuidedStructureStart + 15) % 16)) DB 0
+
+OvmfSevGuidedStructureStart:
+;
+; OvmfSev metadata descriptor
+;
+OvmfSevMetadataGuid:
+
+_DescriptorSev:
+  DB 'A','S','E','V'                                        ; Signature
+  DD OvmfSevGuidedStructureEnd - _DescriptorSev             ; Length
+  DD OVMF_SEV_METADATA_VERSION                              ; Version
+  DD (OvmfSevGuidedStructureEnd - _DescriptorSev - 16) / 12 ; Number of sections
+
+OvmfSevGuidedStructureEnd:
+  ALIGN   16
-- 
2.25.1



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