Re: [PATCH] OvmfPkg/AmdSevDxe: Update ConfidentialComputing blob struct definition

Michael Roth <michael.roth@...>

On Fri, May 13, 2022 at 08:32:38AM -0500, Tom Lendacky wrote:
On 5/13/22 08:22, Michael Roth wrote:
The Confidential Computing blob defined here is intended to match the
definition defined by linux guest kernel. Previously, both definitions
relied on natural alignment, but that relies on both OVMF and kernel
being compiled as 64-bit. While there aren't currently any plans to
enable SNP support for 32-bit compilations, the kernel definition has
since been updated to use explicit padding/reserved fields to avoid
this dependency. Update OVMF to match that definition.

No functional changes (for currently-supported environments, at least).

Signed-off-by: Michael Roth <>
Minor nit comment below that can be ignored if desired.

Reviewed-by: Tom Lendacky <>

OvmfPkg/AmdSevDxe/AmdSevDxe.c | 2 ++
OvmfPkg/Include/Guid/ConfidentialComputingSevSnpBlob.h | 6 ++++--
2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/OvmfPkg/AmdSevDxe/AmdSevDxe.c b/OvmfPkg/AmdSevDxe/AmdSevDxe.c
index 662d3c4ccb..ee6d2528d9 100644
--- a/OvmfPkg/AmdSevDxe/AmdSevDxe.c
+++ b/OvmfPkg/AmdSevDxe/AmdSevDxe.c
(UINT64)(UINTN)FixedPcdGet32 (PcdOvmfSnpSecretsBase),
FixedPcdGet32 (PcdOvmfSnpSecretsSize),
+ 0,
(UINT64)(UINTN)FixedPcdGet32 (PcdOvmfCpuidBase),
FixedPcdGet32 (PcdOvmfCpuidSize),
+ 0,
diff --git a/OvmfPkg/Include/Guid/ConfidentialComputingSevSnpBlob.h b/OvmfPkg/Include/Guid/ConfidentialComputingSevSnpBlob.h
index b328310fd0..83620e31b8 100644
--- a/OvmfPkg/Include/Guid/ConfidentialComputingSevSnpBlob.h
+++ b/OvmfPkg/Include/Guid/ConfidentialComputingSevSnpBlob.h
@@ -18,14 +18,16 @@
{ 0x85, 0x54, 0x93, 0xd7, 0x77, 0x91, 0x2d, 0x42 }, \
-typedef struct {
+typedef PACKED struct {
UINT32 Header;
UINT16 Version;
- UINT16 Reserved1;
+ UINT16 Reserved;
Not to be picky, but I would have left this as Reserved1 and then made the
below entries Reserved2 and Reserved3.
Hi Tom,

I updated those to match how the reserved fields are numbered in the
kernel since it seemed like it could cause confusion otherwise. I should
have noted that in the commit log though as it's a somewhat unrelated




UINT64 SecretsPhysicalAddress;
UINT32 SecretsSize;
+ UINT32 Reserved1;
UINT64 CpuidPhysicalAddress;
UINT32 CpuidLSize;
+ UINT32 Reserved2;
extern EFI_GUID gConfidentialComputingSevSnpBlobGuid;

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