[PATCH 3/3] OvmfPkg/PlatformPei: Mark TPM MMIO range as unencrypted for SEV

["Lendacky, Thomas" <thomas.lendacky@amd.com>]

From: Tom Lendacky <thomas.lendacky@amd.com>

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3345

The TPM support in OVMF performs MMIO accesses during the PEI phase. At
this point, MMIO ranges have not been marked un-encyrpted, so an SEV-ES
guest will fail attempting to perform MMIO to an encrypted address.

Read the PcdTpmBaseAddress and mark the specification defined range
(0x5000 in length) as un-encrypted, to allow an SEV-ES guest to process
the MMIO requests.

Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Min Xu <min.m.xu@intel.com>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
---
 OvmfPkg/PlatformPei/PlatformPei.inf |  1 +
 OvmfPkg/PlatformPei/AmdSev.c        | 19 +++++++++++++++++++
 2 files changed, 20 insertions(+)

diff --git a/OvmfPkg/PlatformPei/PlatformPei.inf b/OvmfPkg/PlatformPei/PlatformPei.inf
index 6ef77ba7bb21..de60332e9390 100644
--- a/OvmfPkg/PlatformPei/PlatformPei.inf
+++ b/OvmfPkg/PlatformPei/PlatformPei.inf
@@ -113,6 +113,7 @@ [Pcd]
 
 [FixedPcd]
   gEfiMdePkgTokenSpaceGuid.PcdPciExpressBaseAddress
+  gEfiSecurityPkgTokenSpaceGuid.PcdTpmBaseAddress
   gEmbeddedTokenSpaceGuid.PcdMemoryTypeEfiACPIMemoryNVS
   gEmbeddedTokenSpaceGuid.PcdMemoryTypeEfiACPIReclaimMemory
   gEmbeddedTokenSpaceGuid.PcdMemoryTypeEfiReservedMemoryType
diff --git a/OvmfPkg/PlatformPei/AmdSev.c b/OvmfPkg/PlatformPei/AmdSev.c
index dddffdebda4b..d524929f9e10 100644
--- a/OvmfPkg/PlatformPei/AmdSev.c
+++ b/OvmfPkg/PlatformPei/AmdSev.c
@@ -141,6 +141,7 @@ AmdSevInitialize (
   )
 {
   UINT64                            EncryptionMask;
+  UINT64                            TpmBaseAddress;
   RETURN_STATUS                     PcdStatus;
 
   //
@@ -206,6 +207,24 @@ AmdSevInitialize (
     }
   }
 
+  //
+  // PEI TPM support will perform MMIO accesses, be sure this range is not
+  // marked encrypted.
+  //
+  TpmBaseAddress = PcdGet64 (PcdTpmBaseAddress);
+  if (TpmBaseAddress != 0) {
+    RETURN_STATUS  DecryptStatus;
+
+    DecryptStatus = MemEncryptSevClearPageEncMask (
+                      0,
+                      TpmBaseAddress,
+                      EFI_SIZE_TO_PAGES (0x5000),
+                      FALSE
+                      );
+
+    ASSERT_RETURN_ERROR (DecryptStatus);
+  }
+
   //
   // Check and perform SEV-ES initialization if required.
   //
-- 
2.31.0