[RFC v4 05/13] OvmfPkg/PlatformPei: Set memory encryption PCD when SEV is enabled

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

Secure Encrypted Virtualization (SEV) guest VMs have the concept of
private and shared memory. Private memory is encrypted with the
guest-specific key, while shared memory may be encrypted with hypervisor
key.  Certain types of memory (namely instruction pages and guest page
tables) are always treated as private memory by the hardware.
For data memory, SEV guest VMs can choose which pages they would like
to be private. The choice is done using the standard CPU page tables
using the C-bit. When building the initial page table we mark all the
memory as private.

The patch sets the memory encryption PCD, the PCD is used by DxeCore
when building the initial page table.


Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
 OvmfPkg/OvmfPkgIa32.dsc             |  3 +
 OvmfPkg/OvmfPkgIa32X64.dsc          |  3 +
 OvmfPkg/OvmfPkgX64.dsc              |  3 +
 OvmfPkg/PlatformPei/PlatformPei.inf |  3 +
 OvmfPkg/PlatformPei/Platform.h      |  5 ++
 OvmfPkg/PlatformPei/AmdSev.c        | 62 ++++++++++++++++++++
 OvmfPkg/PlatformPei/Platform.c      |  1 +
 7 files changed, 80 insertions(+)

diff --git a/OvmfPkg/OvmfPkgIa32.dsc b/OvmfPkg/OvmfPkgIa32.dsc
index 265f2d2b6d2f..139d54aa010e 100644
--- a/OvmfPkg/OvmfPkgIa32.dsc
+++ b/OvmfPkg/OvmfPkgIa32.dsc
@@ -530,6 +530,9 @@ [PcdsDynamicDefault]
   gUefiCpuPkgTokenSpaceGuid.PcdCpuMaxLogicalProcessorNumber|64
   gUefiCpuPkgTokenSpaceGuid.PcdCpuApInitTimeOutInMicroSeconds|50000
 
+  # Set memory encryption mask
+  gEfiMdeModulePkgTokenSpaceGuid.PcdPteMemoryEncryptionAddressOrMask|0x0
+
 !if $(SMM_REQUIRE) == TRUE
   gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmSyncMode|0x01
   gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmApSyncTimeout|100000
diff --git a/OvmfPkg/OvmfPkgIa32X64.dsc b/OvmfPkg/OvmfPkgIa32X64.dsc
index 3b50a2dd2d2f..9403f76ce862 100644
--- a/OvmfPkg/OvmfPkgIa32X64.dsc
+++ b/OvmfPkg/OvmfPkgIa32X64.dsc
@@ -538,6 +538,9 @@ [PcdsDynamicDefault]
   gUefiCpuPkgTokenSpaceGuid.PcdCpuMaxLogicalProcessorNumber|64
   gUefiCpuPkgTokenSpaceGuid.PcdCpuApInitTimeOutInMicroSeconds|50000
 
+  # Set memory encryption mask
+  gEfiMdeModulePkgTokenSpaceGuid.PcdPteMemoryEncryptionAddressOrMask|0x0
+
 !if $(SMM_REQUIRE) == TRUE
   gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmSyncMode|0x01
   gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmApSyncTimeout|100000
diff --git a/OvmfPkg/OvmfPkgX64.dsc b/OvmfPkg/OvmfPkgX64.dsc
index 82c73331aa9f..e137143f7afa 100644
--- a/OvmfPkg/OvmfPkgX64.dsc
+++ b/OvmfPkg/OvmfPkgX64.dsc
@@ -537,6 +537,9 @@ [PcdsDynamicDefault]
   gUefiCpuPkgTokenSpaceGuid.PcdCpuMaxLogicalProcessorNumber|64
   gUefiCpuPkgTokenSpaceGuid.PcdCpuApInitTimeOutInMicroSeconds|50000
 
+  # Set memory encryption mask
+  gEfiMdeModulePkgTokenSpaceGuid.PcdPteMemoryEncryptionAddressOrMask|0x0
+
 !if $(SMM_REQUIRE) == TRUE
   gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmSyncMode|0x01
   gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmApSyncTimeout|100000
diff --git a/OvmfPkg/PlatformPei/PlatformPei.inf b/OvmfPkg/PlatformPei/PlatformPei.inf
index 53c6dd445a0e..a9a7a76c7325 100644
--- a/OvmfPkg/PlatformPei/PlatformPei.inf
+++ b/OvmfPkg/PlatformPei/PlatformPei.inf
@@ -29,6 +29,7 @@ [Defines]
 #
 
 [Sources]
+  AmdSev.c
   Cmos.c
   FeatureControl.c
   Fv.c
@@ -60,6 +61,7 @@ [LibraryClasses]
   QemuFwCfgLib
   QemuFwCfgS3Lib
   MtrrLib
+  MemEncryptSevLib
   PcdLib
 
 [Pcd]
@@ -94,6 +96,7 @@ [Pcd]
   gEfiMdeModulePkgTokenSpaceGuid.PcdSetNxForStack
   gEfiMdeModulePkgTokenSpaceGuid.PcdPropertiesTableEnable
   gEfiMdeModulePkgTokenSpaceGuid.PcdAcpiS3Enable
+  gEfiMdeModulePkgTokenSpaceGuid.PcdPteMemoryEncryptionAddressOrMask
   gUefiCpuPkgTokenSpaceGuid.PcdCpuLocalApicBaseAddress
   gUefiCpuPkgTokenSpaceGuid.PcdCpuMaxLogicalProcessorNumber
   gUefiCpuPkgTokenSpaceGuid.PcdCpuApInitTimeOutInMicroSeconds
diff --git a/OvmfPkg/PlatformPei/Platform.h b/OvmfPkg/PlatformPei/Platform.h
index 18f42c3f0ea8..a7729b9df44b 100644
--- a/OvmfPkg/PlatformPei/Platform.h
+++ b/OvmfPkg/PlatformPei/Platform.h
@@ -88,6 +88,11 @@ XenDetect (
   VOID
   );
 
+VOID
+AmdSevInitialize (
+  VOID
+  );
+
 extern BOOLEAN mXen;
 
 VOID
diff --git a/OvmfPkg/PlatformPei/AmdSev.c b/OvmfPkg/PlatformPei/AmdSev.c
new file mode 100644
index 000000000000..26f7c3fdbb13
--- /dev/null
+++ b/OvmfPkg/PlatformPei/AmdSev.c
@@ -0,0 +1,62 @@
+/**@file
+  Initialize Secure Encrypted Virtualization (SEV) support
+
+  Copyright (c) 2017, Advanced Micro Devices. All rights reserved.<BR>
+
+  This program and the accompanying materials
+  are licensed and made available under the terms and conditions of the BSD
+  License which accompanies this distribution.  The full text of the license
+  may be found at http://opensource.org/licenses/bsd-license.php
+
+  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
+  WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
+
+**/
+//
+// The package level header files this module uses
+//
+#include <PiPei.h>
+
+#include <Library/DebugLib.h>
+#include <Library/PcdLib.h>
+#include <Register/Cpuid.h>
+#include <Register/Amd/Cpuid.h>
+#include <Library/MemEncryptSevLib.h>
+
+/**
+
+  Function checks if SEV support is available, if present then it sets
+  the dynamic PcdPteMemoryEncryptionAddressOrMask with memory encryption mask.
+
+  **/
+VOID
+EFIAPI
+AmdSevInitialize (
+  VOID
+  )
+{
+  CPUID_MEMORY_ENCRYPTION_INFO_EBX  Ebx;
+  UINT64                            EncryptionMask;
+  RETURN_STATUS                     PcdStatus;
+
+  //
+  // Check if SEV is enabled
+  //
+  if (!MemEncryptSevIsEnabled ()) {
+    return;
+  }
+
+  //
+  // CPUID Fn8000_001F[EBX] Bit 0:5 (memory encryption bit position)
+  //
+  AsmCpuid (CPUID_MEMORY_ENCRYPTION_INFO, NULL, &Ebx.Uint32, NULL, NULL);
+  EncryptionMask = LShiftU64 (1, Ebx.Bits.PtePosBits);
+
+  //
+  // Set Memory Encryption Mask PCD
+  //
+  PcdStatus = PcdSet64S (PcdPteMemoryEncryptionAddressOrMask, EncryptionMask);
+  ASSERT_RETURN_ERROR (PcdStatus);
+
+  DEBUG ((DEBUG_INFO, "SEV is enabled (mask 0x%lx)\n", EncryptionMask));
+}
diff --git a/OvmfPkg/PlatformPei/Platform.c b/OvmfPkg/PlatformPei/Platform.c
index 5e983a8dcea9..5121e337bdcb 100644
--- a/OvmfPkg/PlatformPei/Platform.c
+++ b/OvmfPkg/PlatformPei/Platform.c
@@ -678,6 +678,7 @@ InitializePlatform (
     NoexecDxeInitialization ();
   }
 
+  AmdSevInitialize ();
   MiscInitialization ();
   InstallFeatureControlCallback ();
 
-- 
2.7.4