OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlashDxe.c

   1 /** @file
   2   OVMF support for QEMU system firmware flash device: functions specific to the
   3   runtime DXE driver build.
   4
   5   Copyright (C) 2015, Red Hat, Inc.
   6   Copyright (c) 2009 - 2013, Intel Corporation. All rights reserved.<BR>
   7
   8   SPDX-License-Identifier: BSD-2-Clause-Patent
   9
  10 **/
  11
  12 #include <Library/UefiRuntimeLib.h>
  13 #include <Library/MemEncryptSevLib.h>
  14 #include <Library/VmgExitLib.h>
  15 #include <Register/Amd/Msr.h>
  16
  17 #include "QemuFlash.h"
  18
  19 STATIC EFI_PHYSICAL_ADDRESS  mSevEsFlashPhysBase;
  20
  21 VOID
  22 QemuFlashConvertPointers (
  23   VOID
  24   )
  25 {
  26   if (MemEncryptSevEsIsEnabled ()) {
  27     mSevEsFlashPhysBase = (UINTN)mFlashBase;
  28   }
  29
  30   EfiConvertPointer (0x0, (VOID **)&mFlashBase);
  31 }
  32
  33 VOID
  34 QemuFlashBeforeProbe (
  35   IN  EFI_PHYSICAL_ADDRESS  BaseAddress,
  36   IN  UINTN                 FdBlockSize,
  37   IN  UINTN                 FdBlockCount
  38   )
  39 {
  40   //
  41   // Do nothing
  42   //
  43 }
  44
  45 /**
  46   Write to QEMU Flash
  47
  48   @param[in] Ptr    Pointer to the location to write.
  49   @param[in] Value  The value to write.
  50
  51 **/
  52 VOID
  53 QemuFlashPtrWrite (
  54   IN        volatile UINT8  *Ptr,
  55   IN        UINT8           Value
  56   )
  57 {
  58   if (MemEncryptSevEsIsEnabled ()) {
  59     MSR_SEV_ES_GHCB_REGISTER  Msr;
  60     GHCB                      *Ghcb;
  61     EFI_PHYSICAL_ADDRESS      PhysAddr;
  62     BOOLEAN                   InterruptState;
  63
  64     Msr.GhcbPhysicalAddress = AsmReadMsr64 (MSR_SEV_ES_GHCB);
  65     Ghcb                    = Msr.Ghcb;
  66
  67     //
  68     // The MMIO write needs to be to the physical address of the flash pointer.
  69     // Since this service is available as part of the EFI runtime services,
  70     // account for a non-identity mapped VA after SetVirtualAddressMap().
  71     //
  72     if (mSevEsFlashPhysBase == 0) {
  73       PhysAddr = (UINTN)Ptr;
  74     } else {
  75       PhysAddr = mSevEsFlashPhysBase + (Ptr - mFlashBase);
  76     }
  77
  78     //
  79     // Writing to flash is emulated by the hypervisor through the use of write
  80     // protection. This won't work for an SEV-ES guest because the write won't
  81     // be recognized as a true MMIO write, which would result in the required
  82     // #VC exception. Instead, use the the VMGEXIT MMIO write support directly
  83     // to perform the update.
  84     //
  85     VmgInit (Ghcb, &InterruptState);
  86     Ghcb->SharedBuffer[0]    = Value;
  87     Ghcb->SaveArea.SwScratch = (UINT64)(UINTN)Ghcb->SharedBuffer;
  88     VmgSetOffsetValid (Ghcb, GhcbSwScratch);
  89     VmgExit (Ghcb, SVM_EXIT_MMIO_WRITE, PhysAddr, 1);
  90     VmgDone (Ghcb, InterruptState);
  91   } else {
  92     *Ptr = Value;
  93   }
  94 }