OvmfPkg/Library/XenHypercallLib/X86XenHypercall.c

   1 /** @file
   2   Xen Hypercall Library implementation for Intel architecture
   3
   4 Copyright (c) 2014, Linaro Ltd. All rights reserved.<BR>
   5 This program and the accompanying materials are licensed and made available under
   6 the terms and conditions of the BSD License that accompanies this distribution.
   7 The full text of the license may be found at
   8 http://opensource.org/licenses/bsd-license.php.
   9
  10 THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  11 WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  12
  13 **/
  14
  15 #include <PiDxe.h>
  16 #include <Library/HobLib.h>
  17 #include <Library/DebugLib.h>
  18 #include <Guid/XenInfo.h>
  19
  20 STATIC VOID    *HyperPage;
  21
  22 /**
  23   Check if the Xen Hypercall library is able to make calls to the Xen
  24   hypervisor.
  25
  26   Client code should call further functions in this library only if, and after,
  27   this function returns TRUE.
  28
  29   @retval TRUE   Hypercalls are available.
  30   @retval FALSE  Hypercalls are not available.
  31 **/
  32 BOOLEAN
  33 EFIAPI
  34 XenHypercallIsAvailable (
  35   VOID
  36   )
  37 {
  38   return HyperPage != NULL;
  39 }
  40
  41 //
  42 // Interface exposed by the ASM implementation of the core hypercall
  43 //
  44 INTN
  45 EFIAPI
  46 __XenHypercall2 (
  47   IN     VOID *HypercallAddr,
  48   IN OUT INTN Arg1,
  49   IN OUT INTN Arg2
  50   );
  51
  52 /**
  53   Library constructor: retrieves the Hyperpage address
  54   from the gEfiXenInfoGuid HOB
  55 **/
  56
  57 RETURN_STATUS
  58 EFIAPI
  59 XenHypercallLibInit (
  60   VOID
  61   )
  62 {
  63   EFI_HOB_GUID_TYPE   *GuidHob;
  64   EFI_XEN_INFO        *XenInfo;
  65
  66   GuidHob = GetFirstGuidHob (&gEfiXenInfoGuid);
  67   if (GuidHob == NULL) {
  68     //
  69     // We don't fail library construction, since that has catastrophic
  70     // consequences for client modules (whereas those modules may easily be
  71     // running on a non-Xen platform). Instead, XenHypercallIsAvailable() above
  72     // will return FALSE.
  73     //
  74     return RETURN_SUCCESS;
  75   }
  76   XenInfo = (EFI_XEN_INFO *) GET_GUID_HOB_DATA (GuidHob);
  77   HyperPage = XenInfo->HyperPages;
  78   return RETURN_SUCCESS;
  79 }
  80
  81 /**
  82   This function will put the two arguments in the right place (registers) and
  83   invoke the hypercall identified by HypercallID.
  84
  85   @param HypercallID    The symbolic ID of the hypercall to be invoked
  86   @param Arg1           First argument.
  87   @param Arg2           Second argument.
  88
  89   @return   Return 0 if success otherwise it return an errno.
  90 **/
  91 INTN
  92 EFIAPI
  93 XenHypercall2 (
  94   IN     UINTN  HypercallID,
  95   IN OUT INTN   Arg1,
  96   IN OUT INTN   Arg2
  97   )
  98 {
  99   ASSERT (HyperPage != NULL);
 100
 101   return __XenHypercall2 ((UINT8*)HyperPage + HypercallID * 32, Arg1, Arg2);
 102 }