OvmfPkg/XenBusDxe/GrantTable.c

   1 /** @file
   2   Grant Table function implementation.
   3
   4   Grant Table are used to grant access to certain page of the current
   5   VM to an other VM.
   6
   7   Author: Steven Smith (sos22@cam.ac.uk)
   8   Changes: Grzegorz Milos (gm281@cam.ac.uk)
   9   Copyright (C) 2006, Cambridge University
  10   Copyright (C) 2014, Citrix Ltd.
  11
  12   SPDX-License-Identifier: BSD-2-Clause-Patent
  13 **/
  14 #include "XenBusDxe.h"
  15
  16 #include <IndustryStandard/Xen/memory.h>
  17
  18 #include <Library/XenHypercallLib.h>
  19 #include <Library/SynchronizationLib.h>
  20
  21 #include "GrantTable.h"
  22
  23 #define NR_RESERVED_ENTRIES  8
  24
  25 #define NR_GRANT_FRAMES   (FixedPcdGet32 (PcdXenGrantFrames))
  26 #define NR_GRANT_ENTRIES  (NR_GRANT_FRAMES * EFI_PAGE_SIZE / sizeof(grant_entry_v1_t))
  27
  28 STATIC grant_entry_v1_t  *GrantTable = NULL;
  29 STATIC grant_ref_t       GrantList[NR_GRANT_ENTRIES];
  30 STATIC EFI_LOCK          mGrantListLock;
  31 #ifdef GNT_DEBUG
  32 STATIC BOOLEAN  GrantInUseList[NR_GRANT_ENTRIES];
  33 #endif
  34
  35 STATIC
  36 VOID
  37 XenGrantTablePutFreeEntry (
  38   grant_ref_t  Ref
  39   )
  40 {
  41   EfiAcquireLock (&mGrantListLock);
  42  #ifdef GNT_DEBUG
  43   ASSERT (GrantInUseList[Ref]);
  44   GrantInUseList[Ref] = FALSE;
  45  #endif
  46   GrantList[Ref] = GrantList[0];
  47   GrantList[0]   = Ref;
  48   EfiReleaseLock (&mGrantListLock);
  49 }
  50
  51 STATIC
  52 grant_ref_t
  53 XenGrantTableGetFreeEntry (
  54   VOID
  55   )
  56 {
  57   grant_ref_t  Ref;
  58
  59   EfiAcquireLock (&mGrantListLock);
  60   Ref = GrantList[0];
  61   ASSERT (Ref >= NR_RESERVED_ENTRIES && Ref < NR_GRANT_ENTRIES);
  62   GrantList[0] = GrantList[Ref];
  63  #ifdef GNT_DEBUG
  64   ASSERT (!GrantInUseList[Ref]);
  65   GrantInUseList[Ref] = TRUE;
  66  #endif
  67   EfiReleaseLock (&mGrantListLock);
  68   return Ref;
  69 }
  70
  71 STATIC
  72 grant_ref_t
  73 XenGrantTableGrantAccess (
  74   IN domid_t  DomainId,
  75   IN UINTN    Frame,
  76   IN BOOLEAN  ReadOnly
  77   )
  78 {
  79   grant_ref_t  Ref;
  80   UINT16       Flags;
  81
  82   ASSERT (GrantTable != NULL);
  83   Ref                   = XenGrantTableGetFreeEntry ();
  84   GrantTable[Ref].frame = (UINT32)Frame;
  85   GrantTable[Ref].domid = DomainId;
  86   MemoryFence ();
  87   Flags = GTF_permit_access;
  88   if (ReadOnly) {
  89     Flags |= GTF_readonly;
  90   }
  91
  92   GrantTable[Ref].flags = Flags;
  93
  94   return Ref;
  95 }
  96
  97 STATIC
  98 EFI_STATUS
  99 XenGrantTableEndAccess (
 100   grant_ref_t  Ref
 101   )
 102 {
 103   UINT16  Flags, OldFlags;
 104
 105   ASSERT (GrantTable != NULL);
 106   ASSERT (Ref >= NR_RESERVED_ENTRIES && Ref < NR_GRANT_ENTRIES);
 107
 108   OldFlags = GrantTable[Ref].flags;
 109   do {
 110     if ((Flags = OldFlags) & (GTF_reading | GTF_writing)) {
 111       DEBUG ((DEBUG_WARN, "WARNING: g.e. still in use! (%x)\n", Flags));
 112       return EFI_NOT_READY;
 113     }
 114
 115     OldFlags = InterlockedCompareExchange16 (&GrantTable[Ref].flags, Flags, 0);
 116   } while (OldFlags != Flags);
 117
 118   XenGrantTablePutFreeEntry (Ref);
 119   return EFI_SUCCESS;
 120 }
 121
 122 VOID
 123 XenGrantTableInit (
 124   IN XENBUS_DEVICE  *Dev
 125   )
 126 {
 127   xen_add_to_physmap_t  Parameters;
 128   INTN                  Index;
 129   INTN                  ReturnCode;
 130
 131  #ifdef GNT_DEBUG
 132   SetMem (GrantInUseList, sizeof (GrantInUseList), 1);
 133  #endif
 134   EfiInitializeLock (&mGrantListLock, TPL_NOTIFY);
 135   for (Index = NR_RESERVED_ENTRIES; Index < NR_GRANT_ENTRIES; Index++) {
 136     XenGrantTablePutFreeEntry ((grant_ref_t)Index);
 137   }
 138
 139   GrantTable = (VOID *)(UINTN)Dev->XenIo->GrantTableAddress;
 140   for (Index = 0; Index < NR_GRANT_FRAMES; Index++) {
 141     Parameters.domid = DOMID_SELF;
 142     Parameters.idx   = Index;
 143     Parameters.space = XENMAPSPACE_grant_table;
 144     Parameters.gpfn  = (xen_pfn_t)((UINTN)GrantTable >> EFI_PAGE_SHIFT) + Index;
 145     ReturnCode       = XenHypercallMemoryOp (XENMEM_add_to_physmap, &Parameters);
 146     if (ReturnCode != 0) {
 147       DEBUG ((
 148         DEBUG_ERROR,
 149         "Xen GrantTable, add_to_physmap hypercall error: %Ld\n",
 150         (INT64)ReturnCode
 151         ));
 152     }
 153   }
 154 }
 155
 156 VOID
 157 XenGrantTableDeinit (
 158   XENBUS_DEVICE  *Dev
 159   )
 160 {
 161   INTN                       ReturnCode, Index;
 162   xen_remove_from_physmap_t  Parameters;
 163
 164   if (GrantTable == NULL) {
 165     return;
 166   }
 167
 168   for (Index = NR_GRANT_FRAMES - 1; Index >= 0; Index--) {
 169     Parameters.domid = DOMID_SELF;
 170     Parameters.gpfn  = (xen_pfn_t)((UINTN)GrantTable >> EFI_PAGE_SHIFT) + Index;
 171     DEBUG ((
 172       DEBUG_INFO,
 173       "Xen GrantTable, removing %Lx\n",
 174       (UINT64)Parameters.gpfn
 175       ));
 176     ReturnCode = XenHypercallMemoryOp (XENMEM_remove_from_physmap, &Parameters);
 177     if (ReturnCode != 0) {
 178       DEBUG ((
 179         DEBUG_ERROR,
 180         "Xen GrantTable, remove_from_physmap hypercall error: %Ld\n",
 181         (INT64)ReturnCode
 182         ));
 183     }
 184   }
 185
 186   GrantTable = NULL;
 187 }
 188
 189 EFI_STATUS
 190 EFIAPI
 191 XenBusGrantAccess (
 192   IN  XENBUS_PROTOCOL  *This,
 193   IN  domid_t          DomainId,
 194   IN  UINTN            Frame, // MFN
 195   IN  BOOLEAN          ReadOnly,
 196   OUT grant_ref_t      *RefPtr
 197   )
 198 {
 199   *RefPtr = XenGrantTableGrantAccess (DomainId, Frame, ReadOnly);
 200   return EFI_SUCCESS;
 201 }
 202
 203 EFI_STATUS
 204 EFIAPI
 205 XenBusGrantEndAccess (
 206   IN XENBUS_PROTOCOL  *This,
 207   IN grant_ref_t      Ref
 208   )
 209 {
 210   return XenGrantTableEndAccess (Ref);
 211 }