[PATCH v2 1/3] OvmfPkg/MemEncryptHypercallLib: add library to support SEV hypercalls.

["Ashish Kalra" <ashish.kalra@amd.com>]

From: Ashish Kalra <ashish.kalra@amd.com>

Add SEV and SEV-ES hypercall abstraction library to support SEV Page
encryption/deceryption status hypercalls for SEV and SEV-ES guests.

Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Ard Biesheuvel <ard.biesheuvel@arm.com>

Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
---
 OvmfPkg/Include/Library/MemEncryptHypercallLib.h                  |  37 +++++++
 OvmfPkg/Library/MemEncryptHypercallLib/MemEncryptHypercallLib.c   | 105 ++++++++++++++++++++
 OvmfPkg/Library/MemEncryptHypercallLib/MemEncryptHypercallLib.inf |  39 ++++++++
 OvmfPkg/Library/MemEncryptHypercallLib/X64/AsmHelperStub.nasm     |  39 ++++++++
 OvmfPkg/OvmfPkgX64.dsc                                            |   1 +
 5 files changed, 221 insertions(+)

diff --git a/OvmfPkg/Include/Library/MemEncryptHypercallLib.h b/OvmfPkg/Include/Library/MemEncryptHypercallLib.h
new file mode 100644
index 0000000000..cd46a7f2b3
--- /dev/null
+++ b/OvmfPkg/Include/Library/MemEncryptHypercallLib.h
@@ -0,0 +1,37 @@
+/** @file
+
+  Define Secure Encrypted Virtualization (SEV) hypercall library.
+
+  Copyright (c) 2020, AMD Incorporated. All rights reserved.<BR>
+
+  SPDX-License-Identifier: BSD-2-Clause-Patent
+
+**/
+
+#ifndef _MEM_ENCRYPT_HYPERCALL_LIB_H_
+#define _MEM_ENCRYPT_HYPERCALL_LIB_H_
+
+#include <Base.h>
+
+#define SEV_PAGE_ENC_HYPERCALL  12
+
+/**
+ This hyercall is used to notify hypervisor when a page is marked as
+ 'decrypted' (i.e C-bit removed).
+
+ @param[in]   PhysicalAddress       The physical address that is the start address
+                                    of a memory region.
+ @param[in]   Length                The length of memory region
+ @param[in]   Mode                  SetCBit or ClearCBit
+
+**/
+
+VOID
+EFIAPI
+SetMemoryEncDecHypercall3 (
+  IN  UINTN     PhysicalAddress,
+  IN  UINTN     Length,
+  IN  UINTN     Mode
+  );
+
+#endif
diff --git a/OvmfPkg/Library/MemEncryptHypercallLib/MemEncryptHypercallLib.c b/OvmfPkg/Library/MemEncryptHypercallLib/MemEncryptHypercallLib.c
new file mode 100644
index 0000000000..f1136b7d36
--- /dev/null
+++ b/OvmfPkg/Library/MemEncryptHypercallLib/MemEncryptHypercallLib.c
@@ -0,0 +1,105 @@
+/** @file
+
+  Secure Encrypted Virtualization (SEV) hypercall helper library
+
+  Copyright (c) 2020, AMD Incorporated. All rights reserved.<BR>
+
+  SPDX-License-Identifier: BSD-2-Clause-Patent
+
+**/
+
+#include <Uefi.h>
+#include <Uefi/UefiBaseType.h>
+#include <Library/BaseLib.h>
+#include <Library/DebugLib.h>
+#include <Library/VmgExitLib.h>
+#include <Register/Amd/Ghcb.h>
+#include <Register/Amd/Msr.h>
+#include <Library/MemEncryptSevLib.h>
+#include <Library/MemEncryptHypercallLib.h>
+
+//
+// Interface exposed by the ASM implementation of the core hypercall
+//
+//
+
+VOID
+EFIAPI
+SetMemoryEncDecHypercall3AsmStub (
+  IN  UINTN  HypercallNum,
+  IN  UINTN  PhysicalAddress,
+  IN  UINTN  Length,
+  IN  UINTN  Mode
+  );
+
+/**
+ This function returns the current CPU privilege level, implemented
+ in ASM helper stub.
+
+**/
+
+UINT8
+EFIAPI
+GetCurrentCpuPrivilegeLevel (
+  VOID
+  );
+
+STATIC
+VOID
+GhcbSetRegValid (
+  IN OUT GHCB       *Ghcb,
+  IN GHCB_REGISTER  Reg
+  )
+{
+  UINT32  RegIndex;
+  UINT32  RegBit;
+
+  RegIndex = Reg / 8;
+  RegBit   = Reg & 0x07;
+
+  Ghcb->SaveArea.ValidBitmap[RegIndex] |= (1 << RegBit);
+}
+
+VOID
+EFIAPI
+SetMemoryEncDecHypercall3 (
+  IN PHYSICAL_ADDRESS PhysicalAddress,
+  IN UINTN            Pages,
+  IN UINTN            Mode
+  )
+{
+  if (MemEncryptSevEsIsEnabled ()) {
+    MSR_SEV_ES_GHCB_REGISTER  Msr;
+    GHCB                      *Ghcb;
+    BOOLEAN                   InterruptState;
+    UINT64                    Status;
+
+    Msr.GhcbPhysicalAddress = AsmReadMsr64 (MSR_SEV_ES_GHCB);
+    Ghcb = Msr.Ghcb;
+
+    VmgInit (Ghcb, &InterruptState);
+
+    Ghcb->SaveArea.Rax = SEV_PAGE_ENC_HYPERCALL;
+    GhcbSetRegValid (Ghcb, GhcbRax);
+    Ghcb->SaveArea.Rbx = PhysicalAddress;
+    GhcbSetRegValid (Ghcb, GhcbRbx);
+    Ghcb->SaveArea.Rcx = Pages;
+    GhcbSetRegValid (Ghcb, GhcbRcx);
+    Ghcb->SaveArea.Rdx = Mode;
+    GhcbSetRegValid (Ghcb, GhcbRdx);
+    Ghcb->SaveArea.Cpl = GetCurrentCpuPrivilegeLevel();
+    GhcbSetRegValid (Ghcb, GhcbCpl);
+
+    Status = VmgExit (Ghcb, SVM_EXIT_VMMCALL, 0, 0);
+    if (Status) {
+      DEBUG ((DEBUG_ERROR, "SVM_EXIT_VMMCALL failed %lx\n", Status));
+    }
+    VmgDone (Ghcb, InterruptState);
+  } else {
+    SetMemoryEncDecHypercall3AsmStub (
+      SEV_PAGE_ENC_HYPERCALL,
+      PhysicalAddress,
+      Pages,
+      Mode);
+  }
+}
diff --git a/OvmfPkg/Library/MemEncryptHypercallLib/MemEncryptHypercallLib.inf b/OvmfPkg/Library/MemEncryptHypercallLib/MemEncryptHypercallLib.inf
new file mode 100644
index 0000000000..1936fe5b37
--- /dev/null
+++ b/OvmfPkg/Library/MemEncryptHypercallLib/MemEncryptHypercallLib.inf
@@ -0,0 +1,39 @@
+## @file
+#  Library provides the hypervisor helper functions for SEV guest
+#
+# Copyright (c) 2020 Advanced Micro Devices. All rights reserved.<BR>
+#
+#  SPDX-License-Identifier: BSD-2-Clause-Patent
+#
+#
+##
+
+[Defines]
+  INF_VERSION                    = 1.25
+  BASE_NAME                      = MemEncryptHypercallLib
+  FILE_GUID                      = 86f2501e-f128-45f3-91c4-3cff31656ca8
+  MODULE_TYPE                    = BASE
+  VERSION_STRING                 = 1.0
+  LIBRARY_CLASS                  = MemEncryptHypercallLib|SEC PEI_CORE PEIM DXE_DRIVER DXE_RUNTIME_DRIVER DXE_SMM_DRIVER UEFI_DRIVER
+
+#
+# The following information is for reference only and not required by the build
+# tools.
+#
+# VALID_ARCHITECTURES           = IA32 X64
+#
+
+[Packages]
+  MdeModulePkg/MdeModulePkg.dec
+  MdePkg/MdePkg.dec
+  UefiCpuPkg/UefiCpuPkg.dec
+  OvmfPkg/OvmfPkg.dec
+
+[Sources.X64]
+  MemEncryptHypercallLib.c
+  X64/AsmHelperStub.nasm
+
+[LibraryClasses]
+  BaseLib
+  DebugLib
+  VmgExitLib
diff --git a/OvmfPkg/Library/MemEncryptHypercallLib/X64/AsmHelperStub.nasm b/OvmfPkg/Library/MemEncryptHypercallLib/X64/AsmHelperStub.nasm
new file mode 100644
index 0000000000..5d8a7aa85a
--- /dev/null
+++ b/OvmfPkg/Library/MemEncryptHypercallLib/X64/AsmHelperStub.nasm
@@ -0,0 +1,39 @@
+DEFAULT REL
+SECTION .text
+
+; VOID
+; EFIAPI
+; SetMemoryEncDecHypercall3AsmStub (
+;   IN UINT HypercallNum,
+;   IN INTN Arg1,
+;   IN INTN Arg2,
+;   IN INTN Arg3
+;   );
+global ASM_PFX(SetMemoryEncDecHypercall3AsmStub)
+ASM_PFX(SetMemoryEncDecHypercall3AsmStub):
+  ; UEFI calling conventions require RBX to
+  ; be nonvolatile/callee-saved.
+  push rbx
+  ; Copy HypercallNumber to rax
+  mov rax, rcx
+  ; Copy Arg1 to the register expected by KVM
+  mov rbx, rdx
+  ; Copy Arg2 to register expected by KVM
+  mov rcx, r8
+  ; Copy Arg2 to register expected by KVM
+  mov rdx, r9
+  ; Call VMMCALL
+  vmmcall
+  pop rbx
+  ret
+
+; UINT8
+; EFIAPI
+; GetCurrentCpuPrivilegeLevel (
+;   VOID
+;   );
+global ASM_PFX(GetCurrentCpuPrivilegeLevel)
+ASM_PFX(GetCurrentCpuPrivilegeLevel):
+  mov  ax, cs
+  and  al, 0x3
+  ret
diff --git a/OvmfPkg/OvmfPkgX64.dsc b/OvmfPkg/OvmfPkgX64.dsc
index e59ae05b73..97c31c7586 100644
--- a/OvmfPkg/OvmfPkgX64.dsc
+++ b/OvmfPkg/OvmfPkgX64.dsc
@@ -174,6 +174,7 @@
   VirtioLib|OvmfPkg/Library/VirtioLib/VirtioLib.inf
   LoadLinuxLib|OvmfPkg/Library/LoadLinuxLib/LoadLinuxLib.inf
   MemEncryptSevLib|OvmfPkg/Library/BaseMemEncryptSevLib/BaseMemEncryptSevLib.inf
+  MemEncryptHypercallLib|OvmfPkg/Library/MemEncryptHypercallLib/MemEncryptHypercallLib.inf
 !if $(SMM_REQUIRE) == FALSE
   LockBoxLib|OvmfPkg/Library/LockBoxLib/LockBoxBaseLib.inf
 !endif
-- 
2.17.1