From 75b7aa9528bdd05a7ecf4e64a6beb478d31b402c Mon Sep 17 00:00:00 2001

From: Brijesh Singh <brijesh.singh@amd.com>

Date: Fri, 6 Jul 2018 10:00:42 -0500

Subject: [PATCH] OvmfPkg/QemuFlashFvbServicesRuntimeDxe: Restore C-bit

 when SEV is active

AmdSevDxe maps the flash memory range with C=0, but

SetMemorySpaceAttributes() unconditionally resets the C-bit to '1'. Lets

restore the mapping back to C=0.

Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>

Cc: Anthony Perard <anthony.perard@citrix.com>

Cc: Julien Grall <julien.grall@linaro.org>

Cc: Justen Jordan L <jordan.l.justen@intel.com>

Cc: Laszlo Ersek <lersek@redhat.com>

Contributed-under: TianoCore Contribution Agreement 1.1

Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>

Reviewed-by: Laszlo Ersek <lersek@redhat.com>

Regression-tested-by: Laszlo Ersek <lersek@redhat.com>

---

 .../FvbServicesRuntimeDxe.inf                   |  1 +

 .../FwBlockServiceDxe.c                         | 17 +++++++++++++++++

 2 files changed, 18 insertions(+)

diff --git a/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/FvbServicesRuntimeDxe.inf b/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/FvbServicesRuntimeDxe.inf

index d7b4ec06c4..86b244a009 100644

--- a/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/FvbServicesRuntimeDxe.inf

+++ b/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/FvbServicesRuntimeDxe.inf

@@ -53,6 +53,7 @@ [LibraryClasses]

   DebugLib

   DevicePathLib

   DxeServicesTableLib

+  MemEncryptSevLib

   MemoryAllocationLib

   PcdLib

   UefiBootServicesTableLib

diff --git a/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/FwBlockServiceDxe.c b/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/FwBlockServiceDxe.c

index 37deece363..1fbe1342a5 100644

--- a/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/FwBlockServiceDxe.c

+++ b/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/FwBlockServiceDxe.c

@@ -18,6 +18,7 @@

 #include <Library/DebugLib.h>

 #include <Library/DevicePathLib.h>

 #include <Library/DxeServicesTableLib.h>

+#include <Library/MemEncryptSevLib.h>

 #include <Library/PcdLib.h>

 #include <Library/UefiBootServicesTableLib.h>

 #include <Library/UefiRuntimeLib.h>

@@ -203,5 +204,21 @@ MarkIoMemoryRangeForRuntimeAccess (

                   );

   ASSERT_EFI_ERROR (Status);

+  //

+  // When SEV is active, AmdSevDxe mapped the BaseAddress with C=0 but

+  // SetMemorySpaceAttributes() remaps the range with C=1. Let's restore

+  // the mapping so that both guest and hyervisor can access the flash

+  // memory range.

+  //

+  if (MemEncryptSevIsEnabled ()) {

+    Status = MemEncryptSevClearPageEncMask (

+               0,

+               BaseAddress,

+               EFI_SIZE_TO_PAGES (Length),

+               FALSE

+               );

+    ASSERT_EFI_ERROR (Status);

+  }

+

   return Status;

 }

-- 

2.17.1