1 files changed, 119 insertions, 0 deletions
diff --git a/roms/edk2/OvmfPkg/AmdSevDxe/AmdSevDxe.c b/roms/edk2/OvmfPkg/AmdSevDxe/AmdSevDxe.c
new file mode 100644
index 000000000..595586617
--- /dev/null
+++ b/roms/edk2/OvmfPkg/AmdSevDxe/AmdSevDxe.c
@@ -0,0 +1,119 @@
+/** @file
+
+  AMD Sev Dxe driver. This driver is dispatched early in DXE, due to being list
+  in APRIORI. It clears C-bit from MMIO and NonExistent Memory space when SEV
+  is enabled.
+
+  Copyright (c) 2017, AMD Inc. All rights reserved.<BR>
+
+  SPDX-License-Identifier: BSD-2-Clause-Patent
+
+**/
+
+#include <Library/BaseLib.h>
+#include <Library/BaseMemoryLib.h>
+#include <Library/DebugLib.h>
+#include <Library/DxeServicesTableLib.h>
+#include <Library/MemEncryptSevLib.h>
+#include <Library/MemoryAllocationLib.h>
+#include <Library/PcdLib.h>
+
+EFI_STATUS
+EFIAPI
+AmdSevDxeEntryPoint (
+  IN EFI_HANDLE         ImageHandle,
+  IN EFI_SYSTEM_TABLE   *SystemTable
+  )
+{
+  EFI_STATUS                       Status;
+  EFI_GCD_MEMORY_SPACE_DESCRIPTOR  *AllDescMap;
+  UINTN                            NumEntries;
+  UINTN                            Index;
+
+  //
+  // Do nothing when SEV is not enabled
+  //
+  if (!MemEncryptSevIsEnabled ()) {
+    return EFI_UNSUPPORTED;
+  }
+
+  //
+  // Iterate through the GCD map and clear the C-bit from MMIO and NonExistent
+  // memory space. The NonExistent memory space will be used for mapping the
+  // MMIO space added later (eg PciRootBridge). By clearing both known MMIO and
+  // NonExistent memory space can gurantee that current and furture MMIO adds
+  // will have C-bit cleared.
+  //
+  Status = gDS->GetMemorySpaceMap (&NumEntries, &AllDescMap);
+  if (!EFI_ERROR (Status)) {
+    for (Index = 0; Index < NumEntries; Index++) {
+      CONST EFI_GCD_MEMORY_SPACE_DESCRIPTOR *Desc;
+
+      Desc = &AllDescMap[Index];
+      if (Desc->GcdMemoryType == EfiGcdMemoryTypeMemoryMappedIo ||
+          Desc->GcdMemoryType == EfiGcdMemoryTypeNonExistent) {
+        Status = MemEncryptSevClearPageEncMask (
+                   0,
+                   Desc->BaseAddress,
+                   EFI_SIZE_TO_PAGES (Desc->Length),
+                   FALSE
+                   );
+        ASSERT_EFI_ERROR (Status);
+      }
+    }
+
+    FreePool (AllDescMap);
+  }
+
+  //
+  // When SMM is enabled, clear the C-bit from SMM Saved State Area
+  //
+  // NOTES: The SavedStateArea address cleared here is before SMBASE
+  // relocation. Currently, we do not clear the SavedStateArea address after
+  // SMBASE is relocated due to the following reasons:
+  //
+  // 1) Guest BIOS never access the relocated SavedStateArea.
+  //
+  // 2) The C-bit works on page-aligned address, but the SavedStateArea
+  // address is not a page-aligned. Theoretically, we could roundup the address
+  // and clear the C-bit of aligned address but looking carefully we found
+  // that some portion of the page contains code -- which will causes a bigger
+  // issues for SEV guest. When SEV is enabled, all the code must be encrypted
+  // otherwise hardware will cause trap.
+  //
+  // We restore the C-bit for this SMM Saved State Area after SMBASE relocation
+  // is completed (See OvmfPkg/Library/SmmCpuFeaturesLib/SmmCpuFeaturesLib.c).
+  //
+  if (FeaturePcdGet (PcdSmmSmramRequire)) {
+    UINTN MapPagesBase;
+    UINTN MapPagesCount;
+
+    Status = MemEncryptSevLocateInitialSmramSaveStateMapPages (
+               &MapPagesBase,
+               &MapPagesCount
+               );
+    ASSERT_EFI_ERROR (Status);
+
+    //
+    // Although these pages were set aside (i.e., allocated) by PlatformPei, we
+    // could be after a warm reboot from the OS. Don't leak any stale OS data
+    // to the hypervisor.
+    //
+    ZeroMem ((VOID *)MapPagesBase, EFI_PAGES_TO_SIZE (MapPagesCount));
+
+    Status = MemEncryptSevClearPageEncMask (
+               0,             // Cr3BaseAddress -- use current CR3
+               MapPagesBase,  // BaseAddress
+               MapPagesCount, // NumPages
+               TRUE           // Flush
+               );
+    if (EFI_ERROR (Status)) {
+      DEBUG ((DEBUG_ERROR, "%a: MemEncryptSevClearPageEncMask(): %r\n",
+        __FUNCTION__, Status));
+      ASSERT (FALSE);
+      CpuDeadLoop ();
+    }
+  }
+
+  return EFI_SUCCESS;
+}