1 files changed, 109 insertions, 0 deletions
diff --git a/OvmfPkg/Library/VmgExitLib/SecVmgExitVcHandler.c b/OvmfPkg/Library/VmgExitLib/SecVmgExitVcHandler.c
new file mode 100644
index 0000000000..85853d334b
--- /dev/null
+++ b/OvmfPkg/Library/VmgExitLib/SecVmgExitVcHandler.c
@@ -0,0 +1,109 @@
+/** @file
+  X64 #VC Exception Handler functon.
+
+  Copyright (C) 2020, 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/MemEncryptSevLib.h>
+#include <Library/VmgExitLib.h>
+#include <Register/Amd/Msr.h>
+
+#include "VmgExitVcHandler.h"
+
+/**
+  Handle a #VC exception.
+
+  Performs the necessary processing to handle a #VC exception.
+
+  @param[in, out]  ExceptionType  Pointer to an EFI_EXCEPTION_TYPE to be set
+                                  as value to use on error.
+  @param[in, out]  SystemContext  Pointer to EFI_SYSTEM_CONTEXT
+
+  @retval  EFI_SUCCESS            Exception handled
+  @retval  EFI_UNSUPPORTED        #VC not supported, (new) exception value to
+                                  propagate provided
+  @retval  EFI_PROTOCOL_ERROR     #VC handling failed, (new) exception value to
+                                  propagate provided
+
+**/
+EFI_STATUS
+EFIAPI
+VmgExitHandleVc (
+  IN OUT EFI_EXCEPTION_TYPE  *ExceptionType,
+  IN OUT EFI_SYSTEM_CONTEXT  SystemContext
+  )
+{
+  MSR_SEV_ES_GHCB_REGISTER  Msr;
+  GHCB                      *Ghcb;
+  GHCB                      *GhcbBackup;
+  EFI_STATUS                VcRet;
+  BOOLEAN                   InterruptState;
+  SEV_ES_PER_CPU_DATA       *SevEsData;
+
+  InterruptState = GetInterruptState ();
+  if (InterruptState) {
+    DisableInterrupts ();
+  }
+
+  Msr.GhcbPhysicalAddress = AsmReadMsr64 (MSR_SEV_ES_GHCB);
+  ASSERT (Msr.GhcbInfo.Function == 0);
+  ASSERT (Msr.Ghcb != 0);
+
+  Ghcb = Msr.Ghcb;
+  GhcbBackup = NULL;
+
+  SevEsData = (SEV_ES_PER_CPU_DATA *) (Ghcb + 1);
+  SevEsData->VcCount++;
+
+  //
+  // Check for maximum SEC #VC nesting.
+  //
+  if (SevEsData->VcCount > VMGEXIT_MAXIMUM_VC_COUNT) {
+    VmgExitIssueAssert (SevEsData);
+  } else if (SevEsData->VcCount > 1) {
+    UINTN  GhcbBackupSize;
+
+    //
+    // Be sure that the proper amount of pages are allocated
+    //
+    GhcbBackupSize = (VMGEXIT_MAXIMUM_VC_COUNT - 1) * sizeof (*Ghcb);
+    if (GhcbBackupSize > FixedPcdGet32 (PcdOvmfSecGhcbBackupSize)) {
+      //
+      // Not enough SEC backup pages allocated.
+      //
+      VmgExitIssueAssert (SevEsData);
+    }
+
+    //
+    // Save the active GHCB to a backup page.
+    //   To access the correct backup page, increment the backup page pointer
+    //   based on the current VcCount.
+    //
+    GhcbBackup = (GHCB *) FixedPcdGet32 (PcdOvmfSecGhcbBackupBase);
+    GhcbBackup += (SevEsData->VcCount - 2);
+
+    CopyMem (GhcbBackup, Ghcb, sizeof (*Ghcb));
+  }
+
+  VcRet = InternalVmgExitHandleVc (Ghcb, ExceptionType, SystemContext);
+
+  if (GhcbBackup != NULL) {
+    //
+    // Restore the active GHCB from the backup page.
+    //
+    CopyMem (Ghcb, GhcbBackup, sizeof (*Ghcb));
+  }
+
+  SevEsData->VcCount--;
+
+  if (InterruptState) {
+    EnableInterrupts ();
+  }
+
+  return VcRet;
+}