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 SPDX-License-Identifier: BSD-2-Clause-Patent
   6
   7 **/
   8
   9 #include <PiDxe.h>
  10 #include <Library/HobLib.h>
  11 #include <Library/DebugLib.h>
  12 #include <Guid/XenInfo.h>
  13
  14 STATIC VOID    *HyperPage;
  15
  16 /**
  17   Check if the Xen Hypercall library is able to make calls to the Xen
  18   hypervisor.
  19
  20   Client code should call further functions in this library only if, and after,
  21   this function returns TRUE.
  22
  23   @retval TRUE   Hypercalls are available.
  24   @retval FALSE  Hypercalls are not available.
  25 **/
  26 BOOLEAN
  27 EFIAPI
  28 XenHypercallIsAvailable (
  29   VOID
  30   )
  31 {
  32   return HyperPage != NULL;
  33 }
  34
  35 //
  36 // Interface exposed by the ASM implementation of the core hypercall
  37 //
  38 INTN
  39 EFIAPI
  40 __XenHypercall2 (
  41   IN     VOID *HypercallAddr,
  42   IN OUT INTN Arg1,
  43   IN OUT INTN Arg2
  44   );
  45
  46 /**
  47   Library constructor: retrieves the Hyperpage address
  48   from the gEfiXenInfoGuid HOB
  49 **/
  50
  51 RETURN_STATUS
  52 EFIAPI
  53 XenHypercallLibInit (
  54   VOID
  55   )
  56 {
  57   EFI_HOB_GUID_TYPE   *GuidHob;
  58   EFI_XEN_INFO        *XenInfo;
  59
  60   GuidHob = GetFirstGuidHob (&gEfiXenInfoGuid);
  61   if (GuidHob == NULL) {
  62     //
  63     // We don't fail library construction, since that has catastrophic
  64     // consequences for client modules (whereas those modules may easily be
  65     // running on a non-Xen platform). Instead, XenHypercallIsAvailable() above
  66     // will return FALSE.
  67     //
  68     return RETURN_SUCCESS;
  69   }
  70   XenInfo = (EFI_XEN_INFO *) GET_GUID_HOB_DATA (GuidHob);
  71   HyperPage = XenInfo->HyperPages;
  72   return RETURN_SUCCESS;
  73 }
  74
  75 /**
  76   This function will put the two arguments in the right place (registers) and
  77   invoke the hypercall identified by HypercallID.
  78
  79   @param HypercallID    The symbolic ID of the hypercall to be invoked
  80   @param Arg1           First argument.
  81   @param Arg2           Second argument.
  82
  83   @return   Return 0 if success otherwise it return an errno.
  84 **/
  85 INTN
  86 EFIAPI
  87 XenHypercall2 (
  88   IN     UINTN  HypercallID,
  89   IN OUT INTN   Arg1,
  90   IN OUT INTN   Arg2
  91   )
  92 {
  93   ASSERT (HyperPage != NULL);
  94
  95   return __XenHypercall2 ((UINT8*)HyperPage + HypercallID * 32, Arg1, Arg2);
  96 }