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

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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>
This commit is contained in:
Brijesh Singh
2018-07-06 10:00:42 -05:00
committed by Laszlo Ersek
parent 3b3d016b7b
commit 75b7aa9528
2 changed files with 18 additions and 0 deletions
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17
OvmfPkg/QemuFlashFvbServicesRuntimeDxe/FwBlockServiceDxe.c
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@ -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;
}