OvmfPkg: Obtain SEV encryption mask with the new MemEncryptSevLib API

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3108

The early assembler code performs validation for some of the SEV-related
information, specifically the encryption bit position. The new
MemEncryptSevGetEncryptionMask() interface provides access to this
validated value.

To ensure that we always use a validated encryption mask for an SEV-ES
guest, update all locations that use CPUID to calculate the encryption
mask to use the new interface.

Also, clean up some call areas where extra masking was being performed
and where a function call was being used instead of the local variable
that was just set using the function.

Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Ard Biesheuvel <ard.biesheuvel@arm.com>
Cc: Rebecca Cran <rebecca@bsdio.com>
Cc: Peter Grehan <grehan@freebsd.org>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Anthony Perard <anthony.perard@citrix.com>
Cc: Julien Grall <julien@xen.org>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Message-Id: <9de678c0d66443c6cc33e004a4cac0a0223c2ebc.1610045305.git.thomas.lendacky@amd.com>

1 files changed, 2 insertions, 10 deletions

diff --git a/OvmfPkg/XenPlatformPei/AmdSev.c b/OvmfPkg/XenPlatformPei/AmdSev.c
index 7ebbb5cc1f..4ed448632a 100644
--- a/OvmfPkg/XenPlatformPei/AmdSev.c
+++ b/OvmfPkg/XenPlatformPei/AmdSev.c
@@ -1,7 +1,7 @@
 /**@file

   Initialize Secure Encrypted Virtualization (SEV) support

 

-  Copyright (c) 2017, Advanced Micro Devices. All rights reserved.<BR>

+  Copyright (c) 2017 - 2020, Advanced Micro Devices. All rights reserved.<BR>

   Copyright (c) 2019, Citrix Systems, Inc.

 

   SPDX-License-Identifier: BSD-2-Clause-Patent

@@ -14,8 +14,6 @@
 #include <Library/MemEncryptSevLib.h>

 #include <Library/PcdLib.h>

 #include <PiPei.h>

-#include <Register/Amd/Cpuid.h>

-#include <Register/Cpuid.h>

 

 #include "Platform.h"

 

@@ -30,7 +28,6 @@ AmdSevInitialize (
   VOID

   )

 {

-  CPUID_MEMORY_ENCRYPTION_INFO_EBX  Ebx;

   UINT64                            EncryptionMask;

   RETURN_STATUS                     PcdStatus;

 

@@ -42,14 +39,9 @@ AmdSevInitialize (
   }

 

   //

-  // 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

   //

+  EncryptionMask = MemEncryptSevGetEncryptionMask ();

   PcdStatus = PcdSet64S (PcdPteMemoryEncryptionAddressOrMask, EncryptionMask);

   ASSERT_RETURN_ERROR (PcdStatus);