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/** @file
Map TPM MMIO range unencrypted when SEV-ES is active.
Install gOvmfTpmMmioAccessiblePpiGuid unconditionally.
Copyright (C) 2021, Advanced Micro Devices, Inc.
SPDX-License-Identifier: BSD-2-Clause-Patent
**/
#include <PiPei.h>
#include <Library/DebugLib.h>
#include <Library/MemEncryptSevLib.h>
#include <Library/PcdLib.h>
#include <Library/PeiServicesLib.h>
STATIC CONST EFI_PEI_PPI_DESCRIPTOR mTpmMmioRangeAccessible = {
EFI_PEI_PPI_DESCRIPTOR_PPI | EFI_PEI_PPI_DESCRIPTOR_TERMINATE_LIST,
&gOvmfTpmMmioAccessiblePpiGuid,
NULL
};
/**
The entry point for TPM MMIO range mapping driver.
@param[in] FileHandle Handle of the file being invoked.
@param[in] PeiServices Describes the list of possible PEI Services.
@retval EFI_ABORTED No need to keep this PEIM resident
**/
EFI_STATUS
EFIAPI
TpmMmioSevDecryptPeimEntryPoint (
IN EFI_PEI_FILE_HANDLE FileHandle,
IN CONST EFI_PEI_SERVICES **PeiServices
)
{
RETURN_STATUS DecryptStatus;
EFI_STATUS Status;
DEBUG ((DEBUG_INFO, "%a\n", __FUNCTION__));
//
// If SEV is active, MMIO succeeds against an encrypted physical address
// because the nested page fault (NPF) that occurs on access does not
// include the encryption bit in the guest physical address provided to the
// hypervisor.
//
// If SEV-ES is active, MMIO would succeed against an encrypted physical
// address because the #VC handler uses the virtual address (which is an
// identity mapped physical address without the encryption bit) as the guest
// physical address of the MMIO target in the VMGEXIT.
//
// However, if SEV-ES is active, before performing the actual MMIO, an
// additional MMIO mitigation check is performed in the #VC handler to ensure
// that MMIO is being done to/from an unencrypted address. To prevent guest
// termination in this scenario, mark the range unencrypted ahead of access.
//
if (MemEncryptSevEsIsEnabled ()) {
DEBUG ((DEBUG_INFO,
"%a: mapping TPM MMIO address range unencrypted\n",
__FUNCTION__));
DecryptStatus = MemEncryptSevClearPageEncMask (
0,
FixedPcdGet64 (PcdTpmBaseAddress),
EFI_SIZE_TO_PAGES ((UINTN) 0x5000),
FALSE
);
if (RETURN_ERROR (DecryptStatus)) {
DEBUG ((DEBUG_ERROR,
"%a: failed to map TPM MMIO address range unencrypted\n",
__FUNCTION__));
ASSERT_RETURN_ERROR (DecryptStatus);
}
}
//
// MMIO range available
//
Status = PeiServicesInstallPpi (&mTpmMmioRangeAccessible);
ASSERT_EFI_ERROR (Status);
return EFI_ABORTED;
}
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