On Fri, May 13, 2022 at 08:56:06AM -0500, Tom Lendacky wrote:

On 5/13/22 08:22, Michael Roth wrote:

A full-featured SEV-SNP guest will not rely on the AP jump table, and
will instead use the AP Creation interface defined by the GHCB. However,
a guest is still allowed to use the AP jump table if desired.

However, unlike with SEV-ES guests, SEV-SNP guests should not
store/retrieve the jump table address via GHCB requests to the
hypervisor, they should instead store/retrieve it via the SEV-SNP
secrets page. Implement the store side of this for OVMF.

Suggested-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Michael Roth <michael.roth@amd.com>
---
MdePkg/Include/AmdSevSnpSecretsPage.h | 51 +++++++++++++++++++
MdePkg/MdePkg.dec | 4 ++
OvmfPkg/AmdSev/AmdSevX64.dsc | 3 ++
OvmfPkg/CloudHv/CloudHvX64.dsc | 3 ++
OvmfPkg/IntelTdx/IntelTdxX64.dsc | 3 ++
OvmfPkg/Microvm/MicrovmX64.dsc | 3 ++
OvmfPkg/OvmfPkgIa32.dsc | 3 ++
OvmfPkg/OvmfPkgIa32X64.dsc | 3 ++
OvmfPkg/OvmfPkgX64.dsc | 3 ++
OvmfPkg/PlatformPei/AmdSev.c | 5 ++
OvmfPkg/PlatformPei/PlatformPei.inf | 1 +
UefiCpuPkg/Library/MpInitLib/DxeMpInitLib.inf | 1 +
UefiCpuPkg/Library/MpInitLib/DxeMpLib.c | 9 ++++
13 files changed, 92 insertions(+)
create mode 100644 MdePkg/Include/AmdSevSnpSecretsPage.h

diff --git a/MdePkg/Include/AmdSevSnpSecretsPage.h b/MdePkg/Include/AmdSevSnpSecretsPage.h
new file mode 100644
index 0000000000..55c7475ff0
--- /dev/null
+++ b/MdePkg/Include/AmdSevSnpSecretsPage.h

Just wondering if this should be in the MdePkg/Include/Register/Amd directory?

That might be the better spot. I was thinking that was reserved for
definitions related to specific registers, but I somehow missed that it's
also where the GHCB struct is defined. So probably makes sense to put
the secrets page definition there as well.

@@ -0,0 +1,51 @@
+/** @file
+Definitions for AMD SEV-SNP Secrets Page
+
+Copyright (c) 2022 AMD Inc. All rights reserved.<BR>
+SPDX-License-Identifier: BSD-2-Clause-Patent
+
+**/
+
+#ifndef AMD_SEV_SNP_SECRETS_PAGE_H_
+#define AMD_SEV_SNP_SECRETS_PAGE_H_
+
+//
+// OS-defined area of secrets page
+//
+// As defined by "SEV-ES Guest-Hypervisor Communication Block Standardization",
+// revision 1.50, section 2.7, "SEV-SNP Secrets Page".

This should be using at least revision 2.00 (if not 2.01 which is in the
process of being published). 2.01 uses some of the 40-byte reserved area to
hold the high 32-bits of the message sequence numbers (since the SNP API
changed after the GHCB spec was published to convert the sequence numbers
from 32-bit to 64-bit). The changes are backwards compatible, so not a big
deal as to whether to implement since OVMF doesn't make any guest request
API calls.

Okay, will go ahead and update these while I'm at it and send a v2.

Thanks!

-Mike

Thanks,
Tom

+//
+typedef PACKED struct _SNP_SECRETS_OS_AREA {
+ UINT32 MsgSeqNum0;
+ UINT32 MsgSeqNum1;
+ UINT32 MsgSeqNum2;
+ UINT32 MsgSeqNum3;
+ UINT64 ApJumpTablePa;
+ UINT8 Reserved[40];
+ UINT8 GuestUsage[32];
+} SNP_SECRETS_OS_AREA;
+
+#define VMPCK_KEY_LEN 32
+
+//
+// SEV-SNP Secrets page
+//
+// As defined by "SEV-SNP Firmware ABI", revision 1.51, section 8.17.2.5,
+// "PAGE_TYPE_SECRETS".
+//
+typedef PACKED struct _SNP_SECRETS_PAGE {
+ UINT32 Version;
+ UINT32 ImiEn : 1,
+ Reserved : 31;
+ UINT32 Fms;
+ UINT32 Reserved2;
+ UINT8 Gosvw[16];
+ UINT8 Vmpck0[VMPCK_KEY_LEN];
+ UINT8 Vmpck1[VMPCK_KEY_LEN];
+ UINT8 Vmpck2[VMPCK_KEY_LEN];
+ UINT8 Vmpck3[VMPCK_KEY_LEN];
+ SNP_SECRETS_OS_AREA OsArea;
+ UINT8 Reserved3[3840];
+} SNP_SECRETS_PAGE;
+
+#endif
diff --git a/MdePkg/MdePkg.dec b/MdePkg/MdePkg.dec
index f1ebf9e251..a365bfcfe8 100644
--- a/MdePkg/MdePkg.dec
+++ b/MdePkg/MdePkg.dec
@@ -2417,5 +2417,9 @@
# @Prompt Memory encryption attribute
gEfiMdePkgTokenSpaceGuid.PcdConfidentialComputingGuestAttr|0|UINT64|0x0000002e
+ ## This dynamic PCD indicates the location of the SEV-SNP secrets page.
+ # @Prompt SEV-SNP secrets page address
+ gEfiMdePkgTokenSpaceGuid.PcdSevSnpSecretsAddress|0|UINT64|0x0000002f
+
[UserExtensions.TianoCore."ExtraFiles"]
MdePkgExtra.uni
diff --git a/OvmfPkg/AmdSev/AmdSevX64.dsc b/OvmfPkg/AmdSev/AmdSevX64.dsc
index f0700035c1..02306945fd 100644
--- a/OvmfPkg/AmdSev/AmdSevX64.dsc
+++ b/OvmfPkg/AmdSev/AmdSevX64.dsc
@@ -575,6 +575,9 @@
# Set ConfidentialComputing defaults
gEfiMdePkgTokenSpaceGuid.PcdConfidentialComputingGuestAttr|0
+ # Set SEV-SNP Secrets page address default
+ gEfiMdePkgTokenSpaceGuid.PcdSevSnpSecretsAddress|0
+
!include OvmfPkg/OvmfTpmPcds.dsc.inc
gEfiMdePkgTokenSpaceGuid.PcdFSBClock|100000000
diff --git a/OvmfPkg/CloudHv/CloudHvX64.dsc b/OvmfPkg/CloudHv/CloudHvX64.dsc
index d1c85f60c7..7143698253 100644
--- a/OvmfPkg/CloudHv/CloudHvX64.dsc
+++ b/OvmfPkg/CloudHv/CloudHvX64.dsc
@@ -630,6 +630,9 @@
# Set ConfidentialComputing defaults
gEfiMdePkgTokenSpaceGuid.PcdConfidentialComputingGuestAttr|0
+ # Set SEV-SNP Secrets page address default
+ gEfiMdePkgTokenSpaceGuid.PcdSevSnpSecretsAddress|0
+
[PcdsDynamicHii]
!include OvmfPkg/OvmfTpmPcdsHii.dsc.inc
diff --git a/OvmfPkg/IntelTdx/IntelTdxX64.dsc b/OvmfPkg/IntelTdx/IntelTdxX64.dsc
index 80c331ea23..b19718c572 100644
--- a/OvmfPkg/IntelTdx/IntelTdxX64.dsc
+++ b/OvmfPkg/IntelTdx/IntelTdxX64.dsc
@@ -512,6 +512,9 @@
gEfiMdePkgTokenSpaceGuid.PcdFSBClock|100000000
+ # Set SEV-SNP Secrets page address default
+ gEfiMdePkgTokenSpaceGuid.PcdSevSnpSecretsAddress|0
+
################################################################################
#
# Components Section - list of all EDK II Modules needed by this Platform.
diff --git a/OvmfPkg/Microvm/MicrovmX64.dsc b/OvmfPkg/Microvm/MicrovmX64.dsc
index 20c3c9c4d8..42673c29ee 100644
--- a/OvmfPkg/Microvm/MicrovmX64.dsc
+++ b/OvmfPkg/Microvm/MicrovmX64.dsc
@@ -613,6 +613,9 @@
# Set ConfidentialComputing defaults
gEfiMdePkgTokenSpaceGuid.PcdConfidentialComputingGuestAttr|0
+ # Set SEV-SNP Secrets page address default
+ gEfiMdePkgTokenSpaceGuid.PcdSevSnpSecretsAddress|0
+
################################################################################
#
# Components Section - list of all EDK II Modules needed by this Platform.
diff --git a/OvmfPkg/OvmfPkgIa32.dsc b/OvmfPkg/OvmfPkgIa32.dsc
index 533bbdb435..8ffef069a3 100644
--- a/OvmfPkg/OvmfPkgIa32.dsc
+++ b/OvmfPkg/OvmfPkgIa32.dsc
@@ -649,6 +649,9 @@
# Set ConfidentialComputing defaults
gEfiMdePkgTokenSpaceGuid.PcdConfidentialComputingGuestAttr|0
+ # Set SEV-SNP Secrets page address default
+ gEfiMdePkgTokenSpaceGuid.PcdSevSnpSecretsAddress|0
+
!if $(CSM_ENABLE) == FALSE
gEfiMdePkgTokenSpaceGuid.PcdFSBClock|100000000
!endif
diff --git a/OvmfPkg/OvmfPkgIa32X64.dsc b/OvmfPkg/OvmfPkgIa32X64.dsc
index cb68e612bd..0b4d5001b2 100644
--- a/OvmfPkg/OvmfPkgIa32X64.dsc
+++ b/OvmfPkg/OvmfPkgIa32X64.dsc
@@ -657,6 +657,9 @@
# Set ConfidentialComputing defaults
gEfiMdePkgTokenSpaceGuid.PcdConfidentialComputingGuestAttr|0
+ # Set SEV-SNP Secrets page address default
+ gEfiMdePkgTokenSpaceGuid.PcdSevSnpSecretsAddress|0
+
!if $(CSM_ENABLE) == FALSE
gEfiMdePkgTokenSpaceGuid.PcdFSBClock|100000000
!endif
diff --git a/OvmfPkg/OvmfPkgX64.dsc b/OvmfPkg/OvmfPkgX64.dsc
index 71526bba31..3a3223be6b 100644
--- a/OvmfPkg/OvmfPkgX64.dsc
+++ b/OvmfPkg/OvmfPkgX64.dsc
@@ -680,6 +680,9 @@
# Set ConfidentialComputing defaults
gEfiMdePkgTokenSpaceGuid.PcdConfidentialComputingGuestAttr|0
+ # Set SEV-SNP Secrets page address default
+ gEfiMdePkgTokenSpaceGuid.PcdSevSnpSecretsAddress|0
+
!if $(CSM_ENABLE) == FALSE
gEfiMdePkgTokenSpaceGuid.PcdFSBClock|100000000
!endif
diff --git a/OvmfPkg/PlatformPei/AmdSev.c b/OvmfPkg/PlatformPei/AmdSev.c
index 385562b44c..70352ca43b 100644
--- a/OvmfPkg/PlatformPei/AmdSev.c
+++ b/OvmfPkg/PlatformPei/AmdSev.c
@@ -408,6 +408,11 @@ AmdSevInitialize (
//
if (MemEncryptSevSnpIsEnabled ()) {
PcdStatus = PcdSet64S (PcdConfidentialComputingGuestAttr, CCAttrAmdSevSnp);
+ ASSERT_RETURN_ERROR (PcdStatus);
+ PcdStatus = PcdSet64S (
+ PcdSevSnpSecretsAddress,
+ (UINT64)(UINTN)PcdGet32 (PcdOvmfSnpSecretsBase)
+ );
} else if (MemEncryptSevEsIsEnabled ()) {
PcdStatus = PcdSet64S (PcdConfidentialComputingGuestAttr, CCAttrAmdSevEs);
} else {
diff --git a/OvmfPkg/PlatformPei/PlatformPei.inf b/OvmfPkg/PlatformPei/PlatformPei.inf
index 00372fa0eb..c688e4ee24 100644
--- a/OvmfPkg/PlatformPei/PlatformPei.inf
+++ b/OvmfPkg/PlatformPei/PlatformPei.inf
@@ -114,6 +114,7 @@
gEfiMdePkgTokenSpaceGuid.PcdConfidentialComputingGuestAttr
gUefiCpuPkgTokenSpaceGuid.PcdGhcbHypervisorFeatures
gEfiMdeModulePkgTokenSpaceGuid.PcdTdxSharedBitMask
+ gEfiMdePkgTokenSpaceGuid.PcdSevSnpSecretsAddress
[FixedPcd]
gUefiOvmfPkgTokenSpaceGuid.PcdOvmfCpuidBase
diff --git a/UefiCpuPkg/Library/MpInitLib/DxeMpInitLib.inf b/UefiCpuPkg/Library/MpInitLib/DxeMpInitLib.inf
index e1cd0b3500..d8cfddcd82 100644
--- a/UefiCpuPkg/Library/MpInitLib/DxeMpInitLib.inf
+++ b/UefiCpuPkg/Library/MpInitLib/DxeMpInitLib.inf
@@ -80,3 +80,4 @@
gEfiMdeModulePkgTokenSpaceGuid.PcdCpuStackGuard ## CONSUMES
gEfiMdeModulePkgTokenSpaceGuid.PcdGhcbBase ## CONSUMES
gEfiMdePkgTokenSpaceGuid.PcdConfidentialComputingGuestAttr ## CONSUMES
+ gEfiMdePkgTokenSpaceGuid.PcdSevSnpSecretsAddress ## CONSUMES
diff --git a/UefiCpuPkg/Library/MpInitLib/DxeMpLib.c b/UefiCpuPkg/Library/MpInitLib/DxeMpLib.c
index 60d14a5a0e..6014dce136 100644
--- a/UefiCpuPkg/Library/MpInitLib/DxeMpLib.c
+++ b/UefiCpuPkg/Library/MpInitLib/DxeMpLib.c
@@ -15,6 +15,7 @@
#include <Library/VmgExitLib.h>
#include <Register/Amd/Fam17Msr.h>
#include <Register/Amd/Ghcb.h>
+#include <AmdSevSnpSecretsPage.h>
#include <Protocol/Timer.h>
@@ -216,6 +217,14 @@ GetSevEsAPMemory (
DEBUG ((DEBUG_INFO, "Dxe: SevEsAPMemory = %lx\n", (UINTN)StartAddress));
+ if (ConfidentialComputingGuestHas (CCAttrAmdSevSnp)) {
+ SNP_SECRETS_PAGE *Secrets = (SNP_SECRETS_PAGE *)(INTN)PcdGet64 (PcdSevSnpSecretsAddress);
+
+ Secrets->OsArea.ApJumpTablePa = (UINT64)(UINTN)StartAddress;
+
+ return (UINTN)StartAddress;
+ }
+
//
// Save the SevEsAPMemory as the AP jump table.
//