OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgSec.c

   1 /** @file
   2
   3   Stateless fw_cfg library implementation.
   4
   5   Clients must call QemuFwCfgIsAvailable() first.
   6
   7   Copyright (C) 2013, Red Hat, Inc.
   8   Copyright (c) 2011 - 2013, Intel Corporation. All rights reserved.<BR>
   9   Copyright (c) 2017, Advanced Micro Devices. All rights reserved.<BR>
  10
  11   This program and the accompanying materials are licensed and made available
  12   under the terms and conditions of the BSD License which accompanies this
  13   distribution.  The full text of the license may be found at
  14   http://opensource.org/licenses/bsd-license.php
  15
  16   THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS, WITHOUT
  17   WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  18 **/
  19
  20 #include <Library/DebugLib.h>
  21 #include <Library/QemuFwCfgLib.h>
  22
  23 #include "QemuFwCfgLibInternal.h"
  24
  25 /**
  26   Returns a boolean indicating if the firmware configuration interface
  27   is available or not.
  28
  29   This function may change fw_cfg state.
  30
  31   @retval    TRUE   The interface is available
  32   @retval    FALSE  The interface is not available
  33
  34 **/
  35 BOOLEAN
  36 EFIAPI
  37 QemuFwCfgIsAvailable (
  38   VOID
  39   )
  40 {
  41   UINT32 Signature;
  42   UINT32 Revision;
  43
  44   QemuFwCfgSelectItem (QemuFwCfgItemSignature);
  45   Signature = QemuFwCfgRead32 ();
  46   DEBUG ((EFI_D_INFO, "FW CFG Signature: 0x%x\n", Signature));
  47   QemuFwCfgSelectItem (QemuFwCfgItemInterfaceVersion);
  48   Revision = QemuFwCfgRead32 ();
  49   DEBUG ((EFI_D_INFO, "FW CFG Revision: 0x%x\n", Revision));
  50   if ((Signature != SIGNATURE_32 ('Q', 'E', 'M', 'U')) ||
  51       (Revision < 1)
  52      ) {
  53     DEBUG ((EFI_D_INFO, "QemuFwCfg interface not supported.\n"));
  54     return FALSE;
  55   }
  56
  57   DEBUG ((EFI_D_INFO, "QemuFwCfg interface is supported.\n"));
  58   return TRUE;
  59 }
  60
  61
  62 /**
  63   Returns a boolean indicating if the firmware configuration interface is
  64   available for library-internal purposes.
  65
  66   This function never changes fw_cfg state.
  67
  68   @retval    TRUE   The interface is available internally.
  69   @retval    FALSE  The interface is not available internally.
  70 **/
  71 BOOLEAN
  72 InternalQemuFwCfgIsAvailable (
  73   VOID
  74   )
  75 {
  76   //
  77   // We always return TRUE, because the consumer of this library ought to have
  78   // called QemuFwCfgIsAvailable before making other calls which would hit this
  79   // path.
  80   //
  81   return TRUE;
  82 }
  83
  84 /**
  85   Returns a boolean indicating whether QEMU provides the DMA-like access method
  86   for fw_cfg.
  87
  88   @retval    TRUE   The DMA-like access method is available.
  89   @retval    FALSE  The DMA-like access method is unavailable.
  90 **/
  91 BOOLEAN
  92 InternalQemuFwCfgDmaIsAvailable (
  93   VOID
  94   )
  95 {
  96   return FALSE;
  97 }
  98
  99 /**
 100
 101  Returns a boolean indicating whether SEV is enabled
 102
 103  @retval    TRUE    SEV is enabled
 104  @retval    FALSE   SEV is disabled
 105 **/
 106 BOOLEAN
 107 InternalQemuFwCfgSevIsEnabled (
 108   VOID
 109   )
 110 {
 111   //
 112   // DMA is not supported in SEC phase hence SEV support is irrelevant
 113   //
 114   return FALSE;
 115 }
 116
 117 /**
 118  Allocate a bounce buffer for SEV DMA.
 119
 120   @param[in]     NumPage  Number of pages.
 121   @param[out]    Buffer   Allocated DMA Buffer pointer
 122
 123 **/
 124 VOID
 125 InternalQemuFwCfgSevDmaAllocateBuffer (
 126   OUT    VOID     **Buffer,
 127   IN     UINT32   NumPages
 128   )
 129 {
 130   //
 131   // We should never reach here
 132   //
 133   ASSERT (FALSE);
 134 }
 135
 136 /**
 137  Free the DMA buffer allocated using InternalQemuFwCfgSevDmaAllocateBuffer
 138
 139   @param[in]     NumPage  Number of pages.
 140   @param[in]     Buffer   DMA Buffer pointer
 141
 142 **/
 143 VOID
 144 InternalQemuFwCfgSevDmaFreeBuffer (
 145   IN     VOID     *Buffer,
 146   IN     UINT32   NumPages
 147   )
 148 {
 149   //
 150   // We should never reach here
 151   //
 152   ASSERT (FALSE);
 153 }