[PATCH v7 04/31] OvmfPkg: reserve SNP secrets page

["Brijesh Singh" <brijesh.singh@amd.com>]

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

During the SNP guest launch sequence, a special secrets page needs to be
inserted by the VMM. The PSP will populate the page; it will contain the
VM Platform Communication Key (VMPCKs) used by the guest to send and
receive secure messages to the PSP.

The purpose of the secrets page in the SEV-SNP is different from the one
used in SEV guests. In SEV, the secrets page contains the guest owner's
private data after the remote attestation.

Add a new section for the secrets page in the OVMF metadata structure so
that hypervisor can locate it.

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>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
 OvmfPkg/OvmfPkg.dec                      | 6 ++++++
 OvmfPkg/OvmfPkgX64.fdf                   | 3 +++
 OvmfPkg/ResetVector/ResetVector.inf      | 2 ++
 OvmfPkg/ResetVector/ResetVector.nasmb    | 3 +++
 OvmfPkg/ResetVector/X64/OvmfMetadata.asm | 9 +++++++++
 5 files changed, 23 insertions(+)

diff --git a/OvmfPkg/OvmfPkg.dec b/OvmfPkg/OvmfPkg.dec
index c37dafad49bb..6266fdef6054 100644
--- a/OvmfPkg/OvmfPkg.dec
+++ b/OvmfPkg/OvmfPkg.dec
@@ -340,6 +340,12 @@ [PcdsFixedAtBuild]
   # header definition.
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfConfidentialComputingWorkAreaHeader|0|UINT32|0x51
 
+  ## The base address and size of the SEV-SNP Secrets Area that contains
+  #  the VM platform communication key used to send and recieve the
+  #  messages to the PSP. If this is set in the .fdf, the platform
+  #  is responsible to reserve this area from DXE phase overwrites.
+  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSnpSecretsBase|0|UINT32|0x52
+  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSnpSecretsSize|0|UINT32|0x53
 
 [PcdsDynamic, PcdsDynamicEx]
   gUefiOvmfPkgTokenSpaceGuid.PcdEmuVariableEvent|0|UINT64|2
diff --git a/OvmfPkg/OvmfPkgX64.fdf b/OvmfPkg/OvmfPkgX64.fdf
index 23936242e74a..5b871db20ab2 100644
--- a/OvmfPkg/OvmfPkgX64.fdf
+++ b/OvmfPkg/OvmfPkgX64.fdf
@@ -88,6 +88,9 @@ [FD.MEMFD]
 0x00C000|0x001000
 gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbBackupBase|gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbBackupSize
 
+0x00D000|0x001000
+gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSnpSecretsBase|gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSnpSecretsSize
+
 0x010000|0x010000
 gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPeiTempRamBase|gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPeiTempRamSize
 
diff --git a/OvmfPkg/ResetVector/ResetVector.inf b/OvmfPkg/ResetVector/ResetVector.inf
index a2520dde5508..09454d0797e6 100644
--- a/OvmfPkg/ResetVector/ResetVector.inf
+++ b/OvmfPkg/ResetVector/ResetVector.inf
@@ -50,3 +50,5 @@ [FixedPcd]
   gUefiOvmfPkgTokenSpaceGuid.PcdSevLaunchSecretSize
   gUefiOvmfPkgTokenSpaceGuid.PcdQemuHashTableBase
   gUefiOvmfPkgTokenSpaceGuid.PcdQemuHashTableSize
+  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSnpSecretsBase
+  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSnpSecretsSize
diff --git a/OvmfPkg/ResetVector/ResetVector.nasmb b/OvmfPkg/ResetVector/ResetVector.nasmb
index bc61b1d05a24..f7d09acd33ed 100644
--- a/OvmfPkg/ResetVector/ResetVector.nasmb
+++ b/OvmfPkg/ResetVector/ResetVector.nasmb
@@ -77,6 +77,9 @@
   %define SEV_ES_WORK_AREA_RDRAND (FixedPcdGet32 (PcdSevEsWorkAreaBase) + 8)
   %define SEV_ES_WORK_AREA_ENC_MASK (FixedPcdGet32 (PcdSevEsWorkAreaBase) + 16)
   %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))
+
 %include "Ia32/Flat32ToFlat64.asm"
 %include "Ia32/AmdSev.asm"
 %include "Ia32/PageTables64.asm"
diff --git a/OvmfPkg/ResetVector/X64/OvmfMetadata.asm b/OvmfPkg/ResetVector/X64/OvmfMetadata.asm
index a1260a1ed029..bb348e1c6a79 100644
--- a/OvmfPkg/ResetVector/X64/OvmfMetadata.asm
+++ b/OvmfPkg/ResetVector/X64/OvmfMetadata.asm
@@ -23,6 +23,9 @@ BITS  64
 ; The section must be accepted or validated by the VMM before the boot
 %define OVMF_SECTION_TYPE_SEC_MEM     0x102
 
+; AMD SEV-SNP specific sections
+%define OVMF_SECTION_TYPE_SNP_SECRETS 0x200
+
 ALIGN 16
 
 TIMES (15 - ((OvmfGuidedStructureEnd - OvmfGuidedStructureStart + 15) % 16)) DB 0
@@ -41,5 +44,11 @@ _Descriptor:
   DD OVMF_METADATA_VERSION                            ; Version
   DD (OvmfGuidedStructureEnd - _Descriptor - 16) / 12 ; Number of sections
 
+; SEV-SNP Secrets page
+SevSnpSecrets:
+  DD  SEV_SNP_SECRETS_BASE
+  DD  SEV_SNP_SECRETS_SIZE
+  DD  OVMF_SECTION_TYPE_SNP_SECRETS
+
 OvmfGuidedStructureEnd:
   ALIGN   16
-- 
2.17.1