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/** @file
OVMF support for QEMU system firmware flash device: functions specific to the
runtime DXE driver build.
Copyright (C) 2015, Red Hat, Inc.
Copyright (c) 2009 - 2013, Intel Corporation. All rights reserved.<BR>
SPDX-License-Identifier: BSD-2-Clause-Patent
**/
#include <Library/UefiRuntimeLib.h>
#include <Library/MemEncryptSevLib.h>
#include <Library/VmgExitLib.h>
#include <Register/Amd/Msr.h>
#include "QemuFlash.h"
VOID
QemuFlashConvertPointers (
VOID
)
{
EfiConvertPointer (0x0, (VOID **) &mFlashBase);
}
VOID
QemuFlashBeforeProbe (
IN EFI_PHYSICAL_ADDRESS BaseAddress,
IN UINTN FdBlockSize,
IN UINTN FdBlockCount
)
{
//
// Do nothing
//
}
/**
Write to QEMU Flash
@param[in] Ptr Pointer to the location to write.
@param[in] Value The value to write.
**/
VOID
QemuFlashPtrWrite (
IN volatile UINT8 *Ptr,
IN UINT8 Value
)
{
if (MemEncryptSevEsIsEnabled ()) {
MSR_SEV_ES_GHCB_REGISTER Msr;
GHCB *Ghcb;
Msr.GhcbPhysicalAddress = AsmReadMsr64 (MSR_SEV_ES_GHCB);
Ghcb = Msr.Ghcb;
//
// Writing to flash is emulated by the hypervisor through the use of write
// protection. This won't work for an SEV-ES guest because the write won't
// be recognized as a true MMIO write, which would result in the required
// #VC exception. Instead, use the the VMGEXIT MMIO write support directly
// to perform the update.
//
VmgInit (Ghcb);
Ghcb->SharedBuffer[0] = Value;
Ghcb->SaveArea.SwScratch = (UINT64) (UINTN) Ghcb->SharedBuffer;
VmgExit (Ghcb, SVM_EXIT_MMIO_WRITE, (UINT64) (UINTN) Ptr, 1);
VmgDone (Ghcb);
} else {
*Ptr = Value;
}
}
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