OvmfPkg: introduce a common work area

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3429

Both the TDX and SEV support needs to reserve a page in MEMFD as a work
area. The page will contain meta data specific to the guest type.
Currently, the SEV-ES support reserves a page in MEMFD
(PcdSevEsWorkArea) for the work area. This page can be reused as a TDX
work area when Intel TDX is enabled.

Based on the discussion [1], it was agreed to rename the SevEsWorkArea
to the OvmfWorkArea, and add a header that can be used to indicate the
work area type.

[1] https://edk2.groups.io/g/devel/message/78262?p=,,,20,0,0,0::\
    created,0,SNP,20,2,0,84476064

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>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Reviewed-by: Min Xu <min.m.xu@intel.com>
Reviewed-by: Jiewen Yao <Jiewen.yao@intel.com>

OvmfPkg/Include/Library/MemEncryptSevLib.h

@@ -12,6 +12,7 @@
 #define _MEM_ENCRYPT_SEV_LIB_H_
 
 #include <Base.h>
+#include <WorkArea.h>
 
 //
 // Define the maximum number of #VCs allowed (e.g. the level of nesting
@@ -36,26 +37,6 @@ typedef struct {
   VOID    *GhcbBackupPages;
 } SEV_ES_PER_CPU_DATA;
 
-//
-// Internal structure for holding SEV-ES information needed during SEC phase
-// and valid only during SEC phase and early PEI during platform
-// initialization.
-//
-// This structure is also used by assembler files:
-//   OvmfPkg/ResetVector/ResetVector.nasmb
-//   OvmfPkg/ResetVector/Ia32/PageTables64.asm
-//   OvmfPkg/ResetVector/Ia32/Flat32ToFlat64.asm
-// any changes must stay in sync with its usage.
-//
-typedef struct _SEC_SEV_ES_WORK_AREA {
-  UINT8    SevEsEnabled;
-  UINT8    Reserved1[7];
-
-  UINT64   RandomData;
-
-  UINT64   EncryptionMask;
-} SEC_SEV_ES_WORK_AREA;
-
 //
 // Memory encryption address range states.
 //

OvmfPkg/Include/WorkArea.h

@@ -0,0 +1,67 @@
+/** @file
+
+  Work Area structure definition
+
+  Copyright (c) 2021, AMD Inc.
+
+  SPDX-License-Identifier: BSD-2-Clause-Patent
+**/
+
+#ifndef __OVMF_WORK_AREA_H__
+#define __OVMF_WORK_AREA_H__
+
+//
+// Guest type for the work area
+//
+typedef enum {
+  GUEST_TYPE_NON_ENCRYPTED,
+  GUEST_TYPE_AMD_SEV,
+  GUEST_TYPE_INTEL_TDX,
+
+} GUEST_TYPE;
+
+//
+// Confidential computing work area header definition. Any change
+// to the structure need to be kept in sync with the
+// PcdOvmfConfidentialComputingWorkAreaHeader.
+//
+typedef struct _CONFIDENTIAL_COMPUTING_WORK_AREA_HEADER {
+  UINT8                   GuestType;
+  UINT8                   Reserved1[3];
+} CONFIDENTIAL_COMPUTING_WORK_AREA_HEADER;
+
+//
+// Internal structure for holding SEV-ES information needed during SEC phase
+// and valid only during SEC phase and early PEI during platform
+// initialization.
+//
+// This structure is also used by assembler files:
+//   OvmfPkg/ResetVector/ResetVector.nasmb
+//   OvmfPkg/ResetVector/Ia32/PageTables64.asm
+//   OvmfPkg/ResetVector/Ia32/Flat32ToFlat64.asm
+// any changes must stay in sync with its usage.
+//
+typedef struct _SEC_SEV_ES_WORK_AREA {
+  UINT8    SevEsEnabled;
+  UINT8    Reserved1[7];
+
+  UINT64   RandomData;
+
+  UINT64   EncryptionMask;
+} SEC_SEV_ES_WORK_AREA;
+
+//
+// The SEV work area definition.
+//
+typedef struct _SEV_WORK_AREA {
+  CONFIDENTIAL_COMPUTING_WORK_AREA_HEADER   Header;
+
+  SEC_SEV_ES_WORK_AREA                      SevEsWorkArea;
+} SEV_WORK_AREA;
+
+typedef union {
+  CONFIDENTIAL_COMPUTING_WORK_AREA_HEADER   Header;
+  SEV_WORK_AREA                             SevWorkArea;
+} OVMF_WORK_AREA;
+
+#endif

OvmfPkg/OvmfPkg.dec

@@ -329,6 +329,18 @@
   gUefiOvmfPkgTokenSpaceGuid.PcdQemuHashTableBase|0x0|UINT32|0x47
   gUefiOvmfPkgTokenSpaceGuid.PcdQemuHashTableSize|0x0|UINT32|0x48
 
+  ## The base address and size of the work area used during the SEC
+  # phase by the SEV and TDX supports.
+  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfWorkAreaBase|0|UINT32|0x49
+  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfWorkAreaSize|0|UINT32|0x50
+
+  ## The work area contains a fixed size header in the Include/WorkArea.h.
+  # The size of this header is used early boot, and is provided through
+  # a fixed PCD. It need to be kept in sync with any changes to the
+  # header definition.
+  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfConfidentialComputingWorkAreaHeader|0|UINT32|0x51
+
+
 [PcdsDynamic, PcdsDynamicEx]
   gUefiOvmfPkgTokenSpaceGuid.PcdEmuVariableEvent|0|UINT64|2
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfFlashVariablesEnable|FALSE|BOOLEAN|0x10

OvmfPkg/OvmfPkgDefines.fdf.inc

@@ -82,6 +82,12 @@ SET gEfiMdeModulePkgTokenSpaceGuid.PcdFlashNvStorageFtwWorkingSize = $(BLOCK_SIZ
 SET gUefiOvmfPkgTokenSpaceGuid.PcdOvmfFlashNvStorageFtwSpareBase = gUefiOvmfPkgTokenSpaceGuid.PcdOvmfFlashNvStorageFtwWorkingBase + gEfiMdeModulePkgTokenSpaceGuid.PcdFlashNvStorageFtwWorkingSize
 SET gEfiMdeModulePkgTokenSpaceGuid.PcdFlashNvStorageFtwSpareSize = $(VARS_SPARE_SIZE)
 
+# The OVMF WorkArea contains a fixed size header followed by the actual data.
+# The size of header is accessed through a fixed PCD in the reset vector code.
+# The value need to be kept in sync with the any changes to the Confidential
+# Computing Work Area header defined in the Include/WorkArea.h
+SET gUefiOvmfPkgTokenSpaceGuid.PcdOvmfConfidentialComputingWorkAreaHeader  = 4
+
 !if $(SMM_REQUIRE) == TRUE
 SET gEfiMdeModulePkgTokenSpaceGuid.PcdFlashNvStorageVariableBase64 = gUefiOvmfPkgTokenSpaceGuid.PcdOvmfFlashNvStorageVariableBase
 SET gEfiMdeModulePkgTokenSpaceGuid.PcdFlashNvStorageFtwWorkingBase = gUefiOvmfPkgTokenSpaceGuid.PcdOvmfFlashNvStorageFtwWorkingBase

OvmfPkg/OvmfPkgX64.fdf

@@ -83,7 +83,7 @@ gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbPageTableBase|gUefiOvmfPkgTokenSpaceGui
 gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbBase|gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbSize
 
 0x00B000|0x001000
-gUefiCpuPkgTokenSpaceGuid.PcdSevEsWorkAreaBase|gUefiCpuPkgTokenSpaceGuid.PcdSevEsWorkAreaSize
+gUefiOvmfPkgTokenSpaceGuid.PcdOvmfWorkAreaBase|gUefiOvmfPkgTokenSpaceGuid.PcdOvmfWorkAreaSize
 
 0x00C000|0x001000
 gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbBackupBase|gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbBackupSize
@@ -99,6 +99,13 @@ FV = PEIFV
 gUefiOvmfPkgTokenSpaceGuid.PcdOvmfDxeMemFvBase|gUefiOvmfPkgTokenSpaceGuid.PcdOvmfDxeMemFvSize
 FV = DXEFV
 
+##########################################################################################
+# Set the SEV-ES specific work area PCDs
+#
+SET gUefiCpuPkgTokenSpaceGuid.PcdSevEsWorkAreaBase = $(MEMFD_BASE_ADDRESS) +  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfWorkAreaBase + gUefiOvmfPkgTokenSpaceGuid.PcdOvmfConfidentialComputingWorkAreaHeader
+SET gUefiCpuPkgTokenSpaceGuid.PcdSevEsWorkAreaSize = gUefiOvmfPkgTokenSpaceGuid.PcdOvmfWorkAreaSize - gUefiOvmfPkgTokenSpaceGuid.PcdOvmfConfidentialComputingWorkAreaHeader
+##########################################################################################
+
 ################################################################################
 
 [FV.SECFV]

OvmfPkg/PlatformPei/MemDetect.c

@@ -939,9 +939,9 @@ InitializeRamRegions (
     }
 
 #ifdef MDE_CPU_X64
-    if (MemEncryptSevEsIsEnabled ()) {
+    if (FixedPcdGet32 (PcdOvmfWorkAreaSize) != 0) {
       //
-      // If SEV-ES is enabled, reserve the SEV-ES work area.
+      // Reserve the work area.
       //
       // Since this memory range will be used by the Reset Vector on S3
       // resume, it must be reserved as ACPI NVS.
@@ -951,8 +951,8 @@ InitializeRamRegions (
       // such that they would overlap the work area.
       //
       BuildMemoryAllocationHob (
-        (EFI_PHYSICAL_ADDRESS)(UINTN) FixedPcdGet32 (PcdSevEsWorkAreaBase),
+        (EFI_PHYSICAL_ADDRESS)(UINTN) FixedPcdGet32 (PcdOvmfWorkAreaBase),
-        (UINT64)(UINTN) FixedPcdGet32 (PcdSevEsWorkAreaSize),
+        (UINT64)(UINTN) FixedPcdGet32 (PcdOvmfWorkAreaSize),
         mS3Supported ? EfiACPIMemoryNVS : EfiBootServicesData
         );
     }

OvmfPkg/PlatformPei/PlatformPei.inf

@@ -116,8 +116,8 @@
   gEmbeddedTokenSpaceGuid.PcdMemoryTypeEfiRuntimeServicesData
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbBackupBase
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbBackupSize
-  gUefiCpuPkgTokenSpaceGuid.PcdSevEsWorkAreaBase
+  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfWorkAreaBase
-  gUefiCpuPkgTokenSpaceGuid.PcdSevEsWorkAreaSize
+  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfWorkAreaSize
 
 [FeaturePcd]
   gUefiOvmfPkgTokenSpaceGuid.PcdCsmEnable