[RFC PATCH 07/19] OvmfPkg: Add a library to support registering GHCB GPA

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

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3275

An SEV-SNP guest us required to perform GHCB GPA registration before
using a GHCB. See the GHCB spec section 2.5.2 for more details.

Add a library that can be called to perform the GHCB GPA registration.

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: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
 OvmfPkg/Include/Library/GhcbRegisterLib.h           | 27 ++++++
 OvmfPkg/Library/GhcbRegisterLib/GhcbRegisterLib.c   | 97 ++++++++++++++++++++
 OvmfPkg/Library/GhcbRegisterLib/GhcbRegisterLib.inf | 33 +++++++
 OvmfPkg/OvmfPkgX64.dsc                              |  1 +
 4 files changed, 158 insertions(+)

diff --git a/OvmfPkg/Include/Library/GhcbRegisterLib.h b/OvmfPkg/Include/Library/GhcbRegisterLib.h
new file mode 100644
index 0000000000..7d98b6eb36
--- /dev/null
+++ b/OvmfPkg/Include/Library/GhcbRegisterLib.h
@@ -0,0 +1,27 @@
+/** @file
+
+  Declarations of utility functions used for GHCB GPA registration.
+
+  Copyright (C) 2021, AMD Inc, All rights reserved.<BR>
+
+  SPDX-License-Identifier: BSD-2-Clause-Patent
+
+**/
+
+#ifndef _GHCB_REGISTER_LIB_H_
+#define _GHCB_REGISTER_LIB_H_
+
+/**
+
+  This function can be used to register the GHCB GPA.
+
+  @param[in]  Address           The physical address to registered.
+
+**/
+VOID
+EFIAPI
+GhcbRegister (
+  IN  EFI_PHYSICAL_ADDRESS   Address
+  );
+
+#endif // _GHCB_REGISTER_LIB_H_
diff --git a/OvmfPkg/Library/GhcbRegisterLib/GhcbRegisterLib.c b/OvmfPkg/Library/GhcbRegisterLib/GhcbRegisterLib.c
new file mode 100644
index 0000000000..7fe0aad75a
--- /dev/null
+++ b/OvmfPkg/Library/GhcbRegisterLib/GhcbRegisterLib.c
@@ -0,0 +1,97 @@
+/** @file
+  GHCBRegister Support Library.
+
+  Copyright (C) 2021, Advanced Micro Devices, Inc. All rights reserved.<BR>
+  SPDX-License-Identifier: BSD-2-Clause-Patent
+
+**/
+
+#include <Base.h>
+#include <Uefi.h>
+#include <Library/BaseMemoryLib.h>
+#include <Library/VmgExitLib.h>
+#include <Library/GhcbRegisterLib.h>
+#include <Register/Amd/Msr.h>
+
+/**
+  Handle an SEV-SNP/GHCB protocol check failure.
+
+  Notify the hypervisor using the VMGEXIT instruction that the SEV-SNP guest
+  wishes to be terminated.
+
+  @param[in] ReasonCode  Reason code to provide to the hypervisor for the
+                         termination request.
+
+**/
+STATIC
+VOID
+SevEsProtocolFailure (
+  IN UINT8  ReasonCode
+  )
+{
+  MSR_SEV_ES_GHCB_REGISTER  Msr;
+
+  //
+  // Use the GHCB MSR Protocol to request termination by the hypervisor
+  //
+  Msr.GhcbPhysicalAddress = 0;
+  Msr.GhcbTerminate.Function = GHCB_INFO_TERMINATE_REQUEST;
+  Msr.GhcbTerminate.ReasonCodeSet = GHCB_TERMINATE_GHCB;
+  Msr.GhcbTerminate.ReasonCode = ReasonCode;
+  AsmWriteMsr64 (MSR_SEV_ES_GHCB, Msr.GhcbPhysicalAddress);
+
+  AsmVmgExit ();
+
+  ASSERT (FALSE);
+  CpuDeadLoop ();
+}
+
+/**
+
+  This function can be used to register the GHCB GPA.
+
+  @param[in]  Address           The physical address to be registered.
+
+**/
+VOID
+EFIAPI
+GhcbRegister (
+  IN  EFI_PHYSICAL_ADDRESS   Address
+  )
+{
+  MSR_SEV_ES_GHCB_REGISTER  Msr;
+  MSR_SEV_ES_GHCB_REGISTER  CurrentMsr;
+  EFI_PHYSICAL_ADDRESS      GuestFrameNumber;
+
+  GuestFrameNumber = Address >> EFI_PAGE_SHIFT;
+
+  //
+  // Save the current MSR Value
+  //
+  CurrentMsr.GhcbPhysicalAddress = AsmReadMsr64 (MSR_SEV_ES_GHCB);
+
+  //
+  // Use the GHCB MSR Protocol to request to register the GPA.
+  //
+  Msr.GhcbPhysicalAddress = 0;
+  Msr.GhcbGpaRegister.Function = GHCB_INFO_GHCB_GPA_REGISTER_REQUEST;
+  Msr.GhcbGpaRegister.GuestFrameNumber = GuestFrameNumber;
+  AsmWriteMsr64 (MSR_SEV_ES_GHCB, Msr.GhcbPhysicalAddress);
+
+  AsmVmgExit ();
+
+  Msr.GhcbPhysicalAddress = AsmReadMsr64 (MSR_SEV_ES_GHCB);
+
+  //
+  // If hypervisor responded with a different GPA than requested then fail.
+  //
+  if ((Msr.GhcbGpaRegister.Function != GHCB_INFO_GHCB_GPA_REGISTER_RESPONSE) ||
+      (Msr.GhcbGpaRegister.GuestFrameNumber != GuestFrameNumber)) {
+    SevEsProtocolFailure (GHCB_TERMINATE_GHCB_GENERAL);
+  }
+
+  //
+  // Restore the MSR
+  //
+  AsmWriteMsr64 (MSR_SEV_ES_GHCB, CurrentMsr.GhcbPhysicalAddress);
+}
diff --git a/OvmfPkg/Library/GhcbRegisterLib/GhcbRegisterLib.inf b/OvmfPkg/Library/GhcbRegisterLib/GhcbRegisterLib.inf
new file mode 100644
index 0000000000..8cc39ef715
--- /dev/null
+++ b/OvmfPkg/Library/GhcbRegisterLib/GhcbRegisterLib.inf
@@ -0,0 +1,33 @@
+## @file
+#  GHCBRegisterLib Support Library.
+#
+#  Copyright (C) 2021, Advanced Micro Devices, Inc. All rights reserved.<BR>
+#  SPDX-License-Identifier: BSD-2-Clause-Patent
+#
+##
+
+[Defines]
+  INF_VERSION                    = 0x00010005
+  BASE_NAME                      = GhcbRegisterLib
+  FILE_GUID                      = 0e913c15-12cd-430b-8714-ffe85672a77b
+  MODULE_TYPE                    = BASE
+  VERSION_STRING                 = 1.0
+  LIBRARY_CLASS                  = GhcbRegisterLib
+
+#
+# The following information is for reference only and not required by the build tools.
+#
+#  VALID_ARCHITECTURES           = X64
+#
+
+[Sources.common]
+  GhcbRegisterLib.c
+
+[Packages]
+  MdePkg/MdePkg.dec
+  OvmfPkg/OvmfPkg.dec
+  UefiCpuPkg/UefiCpuPkg.dec
+
+[LibraryClasses]
+  BaseLib
+  BaseMemoryLib
diff --git a/OvmfPkg/OvmfPkgX64.dsc b/OvmfPkg/OvmfPkgX64.dsc
index d4d601b444..aa81bf9c66 100644
--- a/OvmfPkg/OvmfPkgX64.dsc
+++ b/OvmfPkg/OvmfPkgX64.dsc
@@ -242,6 +242,7 @@
 [LibraryClasses.common]
   BaseCryptLib|CryptoPkg/Library/BaseCryptLib/BaseCryptLib.inf
   VmgExitLib|OvmfPkg/Library/VmgExitLib/VmgExitLib.inf
+  GhcbRegisterLib|OvmfPkg/Library/GhcbRegisterLib/GhcbRegisterLib.inf
 
 [LibraryClasses.common.SEC]
   TimerLib|OvmfPkg/Library/AcpiTimerLib/BaseRomAcpiTimerLib.inf
-- 
2.17.1