OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPei.c

   1 /** @file
   2
   3   Stateful and implicitly initialized fw_cfg library implementation.
   4
   5   Copyright (C) 2013, Red Hat, Inc.
   6   Copyright (c) 2011 - 2013, Intel Corporation. All rights reserved.<BR>
   7   Copyright (c) 2017, Advanced Micro Devices. All rights reserved.<BR>
   8
   9   This program and the accompanying materials are licensed and made available
  10   under the terms and conditions of the BSD License which accompanies this
  11   distribution.  The full text of the license may be found at
  12   http://opensource.org/licenses/bsd-license.php
  13
  14   THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS, WITHOUT
  15   WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  16 **/
  17
  18 #include <Library/BaseLib.h>
  19 #include <Library/DebugLib.h>
  20 #include <Library/QemuFwCfgLib.h>
  21 #include <Library/MemEncryptSevLib.h>
  22
  23 #include "QemuFwCfgLibInternal.h"
  24
  25 STATIC BOOLEAN mQemuFwCfgSupported = FALSE;
  26 STATIC BOOLEAN mQemuFwCfgDmaSupported;
  27
  28
  29 /**
  30   Returns a boolean indicating if the firmware configuration interface
  31   is available or not.
  32
  33   This function may change fw_cfg state.
  34
  35   @retval    TRUE   The interface is available
  36   @retval    FALSE  The interface is not available
  37
  38 **/
  39 BOOLEAN
  40 EFIAPI
  41 QemuFwCfgIsAvailable (
  42   VOID
  43   )
  44 {
  45   return InternalQemuFwCfgIsAvailable ();
  46 }
  47
  48
  49 RETURN_STATUS
  50 EFIAPI
  51 QemuFwCfgInitialize (
  52   VOID
  53   )
  54 {
  55   UINT32 Signature;
  56   UINT32 Revision;
  57
  58   //
  59   // Enable the access routines while probing to see if it is supported.
  60   // For probing we always use the IO Port (IoReadFifo8()) access method.
  61   //
  62   mQemuFwCfgSupported = TRUE;
  63   mQemuFwCfgDmaSupported = FALSE;
  64
  65   QemuFwCfgSelectItem (QemuFwCfgItemSignature);
  66   Signature = QemuFwCfgRead32 ();
  67   DEBUG ((EFI_D_INFO, "FW CFG Signature: 0x%x\n", Signature));
  68   QemuFwCfgSelectItem (QemuFwCfgItemInterfaceVersion);
  69   Revision = QemuFwCfgRead32 ();
  70   DEBUG ((EFI_D_INFO, "FW CFG Revision: 0x%x\n", Revision));
  71   if ((Signature != SIGNATURE_32 ('Q', 'E', 'M', 'U')) ||
  72       (Revision < 1)
  73      ) {
  74     DEBUG ((EFI_D_INFO, "QemuFwCfg interface not supported.\n"));
  75     mQemuFwCfgSupported = FALSE;
  76     return RETURN_SUCCESS;
  77   }
  78
  79   if ((Revision & FW_CFG_F_DMA) == 0) {
  80     DEBUG ((DEBUG_INFO, "QemuFwCfg interface (IO Port) is supported.\n"));
  81   } else {
  82     //
  83     // If SEV is enabled then we do not support DMA operations in PEI phase.
  84     // This is mainly because DMA in SEV guest requires using bounce buffer
  85     // (which need to allocate dynamic memory and allocating a PAGE size'd
  86     // buffer can be challenge in PEI phase)
  87     //
  88     if (InternalQemuFwCfgSevIsEnabled ()) {
  89       DEBUG ((DEBUG_INFO, "SEV: QemuFwCfg fallback to IO Port interface.\n"));
  90     } else {
  91       mQemuFwCfgDmaSupported = TRUE;
  92       DEBUG ((DEBUG_INFO, "QemuFwCfg interface (DMA) is supported.\n"));
  93     }
  94   }
  95   return RETURN_SUCCESS;
  96 }
  97
  98
  99 /**
 100   Returns a boolean indicating if the firmware configuration interface is
 101   available for library-internal purposes.
 102
 103   This function never changes fw_cfg state.
 104
 105   @retval    TRUE   The interface is available internally.
 106   @retval    FALSE  The interface is not available internally.
 107 **/
 108 BOOLEAN
 109 InternalQemuFwCfgIsAvailable (
 110   VOID
 111   )
 112 {
 113   return mQemuFwCfgSupported;
 114 }
 115
 116 /**
 117   Returns a boolean indicating whether QEMU provides the DMA-like access method
 118   for fw_cfg.
 119
 120   @retval    TRUE   The DMA-like access method is available.
 121   @retval    FALSE  The DMA-like access method is unavailable.
 122 **/
 123 BOOLEAN
 124 InternalQemuFwCfgDmaIsAvailable (
 125   VOID
 126   )
 127 {
 128   return mQemuFwCfgDmaSupported;
 129 }
 130
 131 /**
 132
 133  Returns a boolean indicating whether SEV is enabled
 134
 135  @retval    TRUE    SEV is enabled
 136  @retval    FALSE   SEV is disabled
 137 **/
 138 BOOLEAN
 139 InternalQemuFwCfgSevIsEnabled (
 140   VOID
 141   )
 142 {
 143   return MemEncryptSevIsEnabled ();
 144 }
 145
 146 /**
 147  Allocate a bounce buffer for SEV DMA.
 148
 149   @param[in]     NumPage  Number of pages.
 150   @param[out]    Buffer   Allocated DMA Buffer pointer
 151
 152 **/
 153 VOID
 154 InternalQemuFwCfgSevDmaAllocateBuffer (
 155   OUT    VOID     **Buffer,
 156   IN     UINT32   NumPages
 157   )
 158 {
 159   //
 160   // We should never reach here
 161   //
 162   ASSERT (FALSE);
 163   CpuDeadLoop ();
 164 }
 165
 166 /**
 167  Free the DMA buffer allocated using InternalQemuFwCfgSevDmaAllocateBuffer
 168
 169   @param[in]     NumPage  Number of pages.
 170   @param[in]     Buffer   DMA Buffer pointer
 171
 172 **/
 173 VOID
 174 InternalQemuFwCfgSevDmaFreeBuffer (
 175   IN     VOID     *Buffer,
 176   IN     UINT32   NumPages
 177   )
 178 {
 179   //
 180   // We should never reach here
 181   //
 182   ASSERT (FALSE);
 183   CpuDeadLoop ();
 184 }