[PATCH v3 4/5] OvmfPkg/Tcg2ConfigPei: Mark TPM MMIO range as unencrypted for SEV-ES

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

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

During PEI, the MMIO range for the TPM is marked as encrypted when running
as an SEV guest. While this isn't an issue for an SEV guest because of
the way the nested page fault is handled, it does result in an SEV-ES
guest terminating because of a mitigation check in the #VC handler to
prevent MMIO to an encrypted address. For an SEV-ES guest, this range
must be marked as unencrypted.

Create a new x86 PEIM for TPM support that will map the TPM MMIO range as
unencrypted when SEV-ES is active. The gOvmfTpmMmioAccessiblePpiGuid PPI
will be unconditionally installed before exiting. The PEIM will exit with
the EFI_ABORTED status so that the PEIM does not stay resident. This new
PEIM will depend on the installation of the permanent PEI RAM, by
PlatformPei, so that in case page table splitting is required during the
clearing of the encryption bit, the new page table(s) will be allocated
from permanent PEI RAM.

Update all OVMF Ia32 and X64 build packages to include this new PEIM.

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: Erdem Aktas <erdemaktas@google.com>
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Min Xu <min.m.xu@intel.com>
Cc: Marc-André Lureau <marcandre.lureau@redhat.com>
Cc: Stefan Berger <stefanb@linux.ibm.com>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
---
 OvmfPkg/AmdSev/AmdSevX64.dsc                              |  1 +
 OvmfPkg/OvmfPkgIa32.dsc                                   |  1 +
 OvmfPkg/OvmfPkgIa32X64.dsc                                |  1 +
 OvmfPkg/OvmfPkgX64.dsc                                    |  1 +
 OvmfPkg/AmdSev/AmdSevX64.fdf                              |  1 +
 OvmfPkg/OvmfPkgIa32.fdf                                   |  1 +
 OvmfPkg/OvmfPkgIa32X64.fdf                                |  1 +
 OvmfPkg/OvmfPkgX64.fdf                                    |  1 +
 OvmfPkg/Tcg/TpmMmioSevDecryptPei/TpmMmioSevDecryptPei.inf | 40 +++++++++
 OvmfPkg/Tcg/TpmMmioSevDecryptPei/TpmMmioSevDecryptPeim.c  | 87 ++++++++++++++++++++
 10 files changed, 135 insertions(+)

diff --git a/OvmfPkg/AmdSev/AmdSevX64.dsc b/OvmfPkg/AmdSev/AmdSevX64.dsc
index cdb29d53142d..66bbbc80cd18 100644
--- a/OvmfPkg/AmdSev/AmdSevX64.dsc
+++ b/OvmfPkg/AmdSev/AmdSevX64.dsc
@@ -626,6 +626,7 @@ [Components]
   OvmfPkg/AmdSev/SecretPei/SecretPei.inf
 
 !if $(TPM_ENABLE) == TRUE
+  OvmfPkg/Tcg/TpmMmioSevDecryptPei/TpmMmioSevDecryptPei.inf
   OvmfPkg/Tcg/Tcg2Config/Tcg2ConfigPei.inf
   SecurityPkg/Tcg/TcgPei/TcgPei.inf
   SecurityPkg/Tcg/Tcg2Pei/Tcg2Pei.inf {
diff --git a/OvmfPkg/OvmfPkgIa32.dsc b/OvmfPkg/OvmfPkgIa32.dsc
index 1730b6558b5c..33fbd767903e 100644
--- a/OvmfPkg/OvmfPkgIa32.dsc
+++ b/OvmfPkg/OvmfPkgIa32.dsc
@@ -706,6 +706,7 @@ [Components]
   UefiCpuPkg/CpuMpPei/CpuMpPei.inf
 
 !if $(TPM_ENABLE) == TRUE
+  OvmfPkg/Tcg/TpmMmioSevDecryptPei/TpmMmioSevDecryptPei.inf
   OvmfPkg/Tcg/Tcg2Config/Tcg2ConfigPei.inf
   SecurityPkg/Tcg/TcgPei/TcgPei.inf
   SecurityPkg/Tcg/Tcg2Pei/Tcg2Pei.inf {
diff --git a/OvmfPkg/OvmfPkgIa32X64.dsc b/OvmfPkg/OvmfPkgIa32X64.dsc
index 78a559da0d0b..b13e5cfd9047 100644
--- a/OvmfPkg/OvmfPkgIa32X64.dsc
+++ b/OvmfPkg/OvmfPkgIa32X64.dsc
@@ -719,6 +719,7 @@ [Components.IA32]
   UefiCpuPkg/CpuMpPei/CpuMpPei.inf
 
 !if $(TPM_ENABLE) == TRUE
+  OvmfPkg/Tcg/TpmMmioSevDecryptPei/TpmMmioSevDecryptPei.inf
   OvmfPkg/Tcg/Tcg2Config/Tcg2ConfigPei.inf
   SecurityPkg/Tcg/TcgPei/TcgPei.inf
   SecurityPkg/Tcg/Tcg2Pei/Tcg2Pei.inf {
diff --git a/OvmfPkg/OvmfPkgX64.dsc b/OvmfPkg/OvmfPkgX64.dsc
index a7d747f6b4ab..999738dc39cd 100644
--- a/OvmfPkg/OvmfPkgX64.dsc
+++ b/OvmfPkg/OvmfPkgX64.dsc
@@ -718,6 +718,7 @@ [Components]
   UefiCpuPkg/CpuMpPei/CpuMpPei.inf
 
 !if $(TPM_ENABLE) == TRUE
+  OvmfPkg/Tcg/TpmMmioSevDecryptPei/TpmMmioSevDecryptPei.inf
   OvmfPkg/Tcg/Tcg2Config/Tcg2ConfigPei.inf
   SecurityPkg/Tcg/TcgPei/TcgPei.inf
   SecurityPkg/Tcg/Tcg2Pei/Tcg2Pei.inf {
diff --git a/OvmfPkg/AmdSev/AmdSevX64.fdf b/OvmfPkg/AmdSev/AmdSevX64.fdf
index c0098502aa90..dd0030dbf189 100644
--- a/OvmfPkg/AmdSev/AmdSevX64.fdf
+++ b/OvmfPkg/AmdSev/AmdSevX64.fdf
@@ -147,6 +147,7 @@ [FV.PEIFV]
 INF  OvmfPkg/AmdSev/SecretPei/SecretPei.inf
 
 !if $(TPM_ENABLE) == TRUE
+INF  OvmfPkg/Tcg/TpmMmioSevDecryptPei/TpmMmioSevDecryptPei.inf
 INF  OvmfPkg/Tcg/Tcg2Config/Tcg2ConfigPei.inf
 INF  SecurityPkg/Tcg/TcgPei/TcgPei.inf
 INF  SecurityPkg/Tcg/Tcg2Pei/Tcg2Pei.inf
diff --git a/OvmfPkg/OvmfPkgIa32.fdf b/OvmfPkg/OvmfPkgIa32.fdf
index f400c845b9c9..b3c8b56f3b60 100644
--- a/OvmfPkg/OvmfPkgIa32.fdf
+++ b/OvmfPkg/OvmfPkgIa32.fdf
@@ -162,6 +162,7 @@ [FV.PEIFV]
 INF  UefiCpuPkg/CpuMpPei/CpuMpPei.inf
 
 !if $(TPM_ENABLE) == TRUE
+INF  OvmfPkg/Tcg/TpmMmioSevDecryptPei/TpmMmioSevDecryptPei.inf
 INF  OvmfPkg/Tcg/Tcg2Config/Tcg2ConfigPei.inf
 INF  SecurityPkg/Tcg/TcgPei/TcgPei.inf
 INF  SecurityPkg/Tcg/Tcg2Pei/Tcg2Pei.inf
diff --git a/OvmfPkg/OvmfPkgIa32X64.fdf b/OvmfPkg/OvmfPkgIa32X64.fdf
index d055552fd09f..86592c2364a3 100644
--- a/OvmfPkg/OvmfPkgIa32X64.fdf
+++ b/OvmfPkg/OvmfPkgIa32X64.fdf
@@ -162,6 +162,7 @@ [FV.PEIFV]
 INF  UefiCpuPkg/CpuMpPei/CpuMpPei.inf
 
 !if $(TPM_ENABLE) == TRUE
+INF  OvmfPkg/Tcg/TpmMmioSevDecryptPei/TpmMmioSevDecryptPei.inf
 INF  OvmfPkg/Tcg/Tcg2Config/Tcg2ConfigPei.inf
 INF  SecurityPkg/Tcg/TcgPei/TcgPei.inf
 INF  SecurityPkg/Tcg/Tcg2Pei/Tcg2Pei.inf
diff --git a/OvmfPkg/OvmfPkgX64.fdf b/OvmfPkg/OvmfPkgX64.fdf
index d519f8532822..d6be798fcadd 100644
--- a/OvmfPkg/OvmfPkgX64.fdf
+++ b/OvmfPkg/OvmfPkgX64.fdf
@@ -174,6 +174,7 @@ [FV.PEIFV]
 INF  UefiCpuPkg/CpuMpPei/CpuMpPei.inf
 
 !if $(TPM_ENABLE) == TRUE
+INF  OvmfPkg/Tcg/TpmMmioSevDecryptPei/TpmMmioSevDecryptPei.inf
 INF  OvmfPkg/Tcg/Tcg2Config/Tcg2ConfigPei.inf
 INF  SecurityPkg/Tcg/TcgPei/TcgPei.inf
 INF  SecurityPkg/Tcg/Tcg2Pei/Tcg2Pei.inf
diff --git a/OvmfPkg/Tcg/TpmMmioSevDecryptPei/TpmMmioSevDecryptPei.inf b/OvmfPkg/Tcg/TpmMmioSevDecryptPei/TpmMmioSevDecryptPei.inf
new file mode 100644
index 000000000000..51ad6d0d055d
--- /dev/null
+++ b/OvmfPkg/Tcg/TpmMmioSevDecryptPei/TpmMmioSevDecryptPei.inf
@@ -0,0 +1,40 @@
+## @file
+# Map TPM MMIO range unencrypted when SEV-ES is active.
+# Install gOvmfTpmMmioAccessiblePpiGuid unconditionally.
+#
+# Copyright (C) 2021, Advanced Micro Devices, Inc.
+#
+# SPDX-License-Identifier: BSD-2-Clause-Patent
+##
+
+[Defines]
+  INF_VERSION                    = 1.29
+  BASE_NAME                      = TpmMmioSevDecryptPei
+  FILE_GUID                      = F12F698A-E506-4A1B-B32E-6920E55DA1C4
+  MODULE_TYPE                    = PEIM
+  VERSION_STRING                 = 1.0
+  ENTRY_POINT                    = TpmMmioSevDecryptPeimEntryPoint
+
+[Sources]
+  TpmMmioSevDecryptPeim.c
+
+[Packages]
+  MdePkg/MdePkg.dec
+  OvmfPkg/OvmfPkg.dec
+  SecurityPkg/SecurityPkg.dec
+
+[LibraryClasses]
+  DebugLib
+  MemEncryptSevLib
+  PcdLib
+  PeimEntryPoint
+  PeiServicesLib
+
+[Ppis]
+  gOvmfTpmMmioAccessiblePpiGuid                      ## PRODUCES
+
+[FixedPcd]
+  gEfiSecurityPkgTokenSpaceGuid.PcdTpmBaseAddress    ## CONSUMES
+
+[Depex]
+  gEfiPeiMemoryDiscoveredPpiGuid
diff --git a/OvmfPkg/Tcg/TpmMmioSevDecryptPei/TpmMmioSevDecryptPeim.c b/OvmfPkg/Tcg/TpmMmioSevDecryptPei/TpmMmioSevDecryptPeim.c
new file mode 100644
index 000000000000..df2ad623308d
--- /dev/null
+++ b/OvmfPkg/Tcg/TpmMmioSevDecryptPei/TpmMmioSevDecryptPeim.c
@@ -0,0 +1,87 @@
+/** @file
+  Map TPM MMIO range unencrypted when SEV-ES is active.
+  Install gOvmfTpmMmioAccessiblePpiGuid unconditionally.
+
+  Copyright (C) 2021, Advanced Micro Devices, Inc.
+
+  SPDX-License-Identifier: BSD-2-Clause-Patent
+**/
+
+
+#include <PiPei.h>
+
+#include <Library/DebugLib.h>
+#include <Library/MemEncryptSevLib.h>
+#include <Library/PcdLib.h>
+#include <Library/PeiServicesLib.h>
+
+STATIC CONST EFI_PEI_PPI_DESCRIPTOR  mTpmMmioRangeAccessible = {
+  EFI_PEI_PPI_DESCRIPTOR_PPI | EFI_PEI_PPI_DESCRIPTOR_TERMINATE_LIST,
+  &gOvmfTpmMmioAccessiblePpiGuid,
+  NULL
+};
+
+/**
+  The entry point for TPM MMIO range mapping driver.
+
+  @param[in]  FileHandle   Handle of the file being invoked.
+  @param[in]  PeiServices  Describes the list of possible PEI Services.
+
+  @retval  EFI_ABORTED  No need to keep this PEIM resident
+**/
+EFI_STATUS
+EFIAPI
+TpmMmioSevDecryptPeimEntryPoint (
+  IN       EFI_PEI_FILE_HANDLE  FileHandle,
+  IN CONST EFI_PEI_SERVICES     **PeiServices
+  )
+{
+  RETURN_STATUS                   DecryptStatus;
+  EFI_STATUS                      Status;
+
+  DEBUG ((DEBUG_INFO, "%a\n", __FUNCTION__));
+
+  //
+  // If SEV is active, MMIO succeeds against an encrypted physical address
+  // because the nested page fault (NPF) that occurs on access does not
+  // include the encryption bit in the guest physical address provided to the
+  // hypervisor.
+  //
+  // If SEV-ES is active, MMIO would succeed against an encrypted physical
+  // address because the #VC handler uses the virtual address (which is an
+  // identity mapped physical address without the encryption bit) as the guest
+  // physical address of the MMIO target in the VMGEXIT.
+  //
+  // However, if SEV-ES is active, before performing the actual MMIO, an
+  // additional MMIO mitigation check is performed in the #VC handler to ensure
+  // that MMIO is being done to/from an unencrypted address. To prevent guest
+  // termination in this scenario, mark the range unencrypted ahead of access.
+  //
+  if (MemEncryptSevEsIsEnabled ()) {
+    DEBUG ((DEBUG_INFO,
+      "%a: mapping TPM MMIO address range unencrypted\n",
+      __FUNCTION__));
+
+    DecryptStatus = MemEncryptSevClearPageEncMask (
+                      0,
+                      FixedPcdGet64 (PcdTpmBaseAddress),
+                      EFI_SIZE_TO_PAGES ((UINTN) 0x5000),
+                      FALSE
+                      );
+
+    if (RETURN_ERROR (DecryptStatus)) {
+      DEBUG ((DEBUG_ERROR,
+        "%a: failed to map TPM MMIO address range unencrypted\n",
+        __FUNCTION__));
+      ASSERT_RETURN_ERROR (DecryptStatus);
+    }
+  }
+
+  //
+  // MMIO range available
+  //
+  Status = PeiServicesInstallPpi (&mTpmMmioRangeAccessible);
+  ASSERT_EFI_ERROR (Status);
+
+  return EFI_ABORTED;
+}
-- 
2.31.0