OvmfPkg/QemuFlashFvbServicesRuntimeDxe: Clear C-bit when SEV is active

Commit:24e4ad7 (OvmfPkg: Add AmdSevDxe driver) added a driver which runs
early in DXE phase and clears the C-bit from NonExistent entry -- which
is later split and accommodate the flash MMIO. When SMM is enabled, we
build two sets of page tables; first page table is used when executing
code in non SMM mode (SMM-less-pgtable) and second page table is used
when we are executing code in SMM mode (SMM-pgtable).

During boot time, AmdSevDxe driver clears the C-bit from the
SMM-less-pgtable. But when SMM is enabled, Qemu Flash services are used
from SMM mode.

In this patch we explicitly clear the C-bit from Qemu flash MMIO range
before we probe the flash. When OVMF is built with SMM_REQUIRE then
call to initialize the flash services happen after the SMM-pgtable is
created and processor has served the first SMI. At this time we will
have access to the SMM-pgtable.

Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
[lersek@redhat.com: trivial coding style improvements]
Reviewed-by: Laszlo Ersek <lersek@redhat.com>

5 files changed, 84 insertions, 0 deletions

diff --git a/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/FvbServicesSmm.inf b/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/FvbServicesSmm.inf
index ba2d3679a4..b5c79762c2 100644
--- a/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/FvbServicesSmm.inf
+++ b/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/FvbServicesSmm.inf
@@ -40,6 +40,7 @@
   FwBlockService.c

   FwBlockServiceSmm.c

   QemuFlash.c

+  QemuFlashSmm.c

 

 [Packages]

   MdePkg/MdePkg.dec

@@ -53,6 +54,7 @@
   DevicePathLib

   DxeServicesTableLib

   MemoryAllocationLib

+  MemEncryptSevLib

   PcdLib

   SmmServicesTableLib

   UefiBootServicesTableLib

diff --git a/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlash.c b/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlash.c
index 5677b5ee11..462d9c0322 100644
--- a/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlash.c
+++ b/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlash.c
@@ -244,6 +244,15 @@ QemuFlashInitialize (
   ASSERT(PcdGet32 (PcdOvmfFirmwareFdSize) % mFdBlockSize == 0);

   mFdBlockCount = PcdGet32 (PcdOvmfFirmwareFdSize) / mFdBlockSize;

 

+  //

+  // execute module specific hooks before probing the flash

+  //

+  QemuFlashBeforeProbe (

+    (EFI_PHYSICAL_ADDRESS)(UINTN) mFlashBase,

+    mFdBlockSize,

+    mFdBlockCount

+    );

+

   if (!QemuFlashDetected ()) {

     ASSERT (!FeaturePcdGet (PcdSmmSmramRequire));

     return EFI_WRITE_PROTECTED;

diff --git a/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlash.h b/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlash.h
index 8d83dca7a5..d34a8a19a0 100644
--- a/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlash.h
+++ b/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlash.h
@@ -88,5 +88,12 @@ QemuFlashConvertPointers (
   VOID

   );

 

+VOID

+QemuFlashBeforeProbe (

+  IN  EFI_PHYSICAL_ADDRESS    BaseAddress,

+  IN  UINTN                   FdBlockSize,

+  IN  UINTN                   FdBlockCount

+  );

+

 #endif

 

diff --git a/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlashDxe.c b/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlashDxe.c
index 08ece2beae..332ceafd3f 100644
--- a/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlashDxe.c
+++ b/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlashDxe.c
@@ -26,3 +26,15 @@ QemuFlashConvertPointers (
 {

   EfiConvertPointer (0x0, (VOID **) &mFlashBase);

 }

+

+VOID

+QemuFlashBeforeProbe (

+  IN  EFI_PHYSICAL_ADDRESS    BaseAddress,

+  IN  UINTN                   FdBlockSize,

+  IN  UINTN                   FdBlockCount

+  )

+{

+  //

+  // Do nothing

+  //

+}

diff --git a/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlashSmm.c b/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlashSmm.c
new file mode 100644
index 0000000000..8999ad8d0d
--- /dev/null
+++ b/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlashSmm.c
@@ -0,0 +1,54 @@
+/** @file

+  Define the module hooks used while probing the QEMU flash device.

+

+  Copyright (C) 2018, Advanced Micro Devices. All rights reserved.

+

+  This program and the accompanying materials are licensed and made available

+  under the terms and conditions of the BSD License which accompanies this

+  distribution.  The full text of the license may be found at

+  http://opensource.org/licenses/bsd-license.php

+

+  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,

+  WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.

+

+**/

+

+#include <Library/BaseMemoryLib.h>

+#include <Library/DebugLib.h>

+#include <Library/PcdLib.h>

+#include <Library/MemEncryptSevLib.h>

+

+#include "QemuFlash.h"

+

+VOID

+QemuFlashBeforeProbe (

+  IN  EFI_PHYSICAL_ADDRESS    BaseAddress,

+  IN  UINTN                   FdBlockSize,

+  IN  UINTN                   FdBlockCount

+  )

+{

+  EFI_STATUS              Status;

+

+  ASSERT (FeaturePcdGet (PcdSmmSmramRequire));

+

+  if (!MemEncryptSevIsEnabled ()) {

+    return;

+  }

+

+  //

+  // When SEV is enabled, AmdSevDxe runs early in DXE phase and clears the

+  // C-bit from the NonExistent entry -- which is later split and accommodate

+  // the flash MMIO but the driver runs in non SMM context hence it cleared the

+  // flash ranges from non SMM page table. When SMM is enabled, the flash

+  // services are accessed from the SMM mode hence we explicitly clear the

+  // C-bit on flash ranges from SMM page table.

+  //

+

+  Status = MemEncryptSevClearPageEncMask (

+             0,

+             BaseAddress,

+             EFI_SIZE_TO_PAGES (FdBlockSize * FdBlockCount),

+             FALSE

+             );

+  ASSERT_EFI_ERROR (Status);

+}