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 /* NR_GRANT_FRAMES must be less than or equal to that configured in Xen */
  26 #define NR_GRANT_FRAMES 4
  27 #define NR_GRANT_ENTRIES (NR_GRANT_FRAMES * EFI_PAGE_SIZE / sizeof(grant_entry_v1_t))
  28
  29 STATIC grant_entry_v1_t *GrantTable = NULL;
  30 STATIC grant_ref_t GrantList[NR_GRANT_ENTRIES];
  31 STATIC EFI_LOCK mGrantListLock;
  32 #ifdef GNT_DEBUG
  33 STATIC BOOLEAN GrantInUseList[NR_GRANT_ENTRIES];
  34 #endif
  35
  36 STATIC
  37 VOID
  38 XenGrantTablePutFreeEntry (
  39   grant_ref_t Ref
  40   )
  41 {
  42   EfiAcquireLock (&mGrantListLock);
  43 #ifdef GNT_DEBUG
  44   ASSERT (GrantInUseList[Ref]);
  45   GrantInUseList[Ref] = FALSE;
  46 #endif
  47   GrantList[Ref] = GrantList[0];
  48   GrantList[0] = Ref;
  49   EfiReleaseLock (&mGrantListLock);
  50 }
  51
  52 STATIC
  53 grant_ref_t
  54 XenGrantTableGetFreeEntry (
  55   VOID
  56   )
  57 {
  58   grant_ref_t Ref;
  59
  60   EfiAcquireLock (&mGrantListLock);
  61   Ref = GrantList[0];
  62   ASSERT (Ref >= NR_RESERVED_ENTRIES && Ref < NR_GRANT_ENTRIES);
  63   GrantList[0] = GrantList[Ref];
  64 #ifdef GNT_DEBUG
  65   ASSERT (!GrantInUseList[Ref]);
  66   GrantInUseList[Ref] = TRUE;
  67 #endif
  68   EfiReleaseLock (&mGrantListLock);
  69   return Ref;
  70 }
  71
  72 STATIC
  73 grant_ref_t
  74 XenGrantTableGrantAccess (
  75   IN domid_t  DomainId,
  76   IN UINTN    Frame,
  77   IN BOOLEAN  ReadOnly
  78   )
  79 {
  80   grant_ref_t Ref;
  81   UINT16 Flags;
  82
  83   ASSERT (GrantTable != NULL);
  84   Ref = XenGrantTableGetFreeEntry ();
  85   GrantTable[Ref].frame = (UINT32)Frame;
  86   GrantTable[Ref].domid = DomainId;
  87   MemoryFence ();
  88   Flags = GTF_permit_access;
  89   if (ReadOnly) {
  90     Flags |= GTF_readonly;
  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 ((EFI_D_WARN, "WARNING: g.e. still in use! (%x)\n", Flags));
 112       return EFI_NOT_READY;
 113     }
 114     OldFlags = InterlockedCompareExchange16 (&GrantTable[Ref].flags, Flags, 0);
 115   } while (OldFlags != Flags);
 116
 117   XenGrantTablePutFreeEntry (Ref);
 118   return EFI_SUCCESS;
 119 }
 120
 121 VOID
 122 XenGrantTableInit (
 123   IN XENBUS_DEVICE  *Dev
 124   )
 125 {
 126   xen_add_to_physmap_t Parameters;
 127   INTN Index;
 128   INTN ReturnCode;
 129
 130 #ifdef GNT_DEBUG
 131   SetMem(GrantInUseList, sizeof (GrantInUseList), 1);
 132 #endif
 133   EfiInitializeLock (&mGrantListLock, TPL_NOTIFY);
 134   for (Index = NR_RESERVED_ENTRIES; Index < NR_GRANT_ENTRIES; Index++) {
 135     XenGrantTablePutFreeEntry ((grant_ref_t)Index);
 136   }
 137
 138   GrantTable = (VOID*)(UINTN) Dev->XenIo->GrantTableAddress;
 139   for (Index = 0; Index < NR_GRANT_FRAMES; Index++) {
 140     Parameters.domid = DOMID_SELF;
 141     Parameters.idx = Index;
 142     Parameters.space = XENMAPSPACE_grant_table;
 143     Parameters.gpfn = (xen_pfn_t) ((UINTN) GrantTable >> EFI_PAGE_SHIFT) + Index;
 144     ReturnCode = XenHypercallMemoryOp (XENMEM_add_to_physmap, &Parameters);
 145     if (ReturnCode != 0) {
 146       DEBUG ((EFI_D_ERROR,
 147         "Xen GrantTable, add_to_physmap hypercall error: %Ld\n",
 148         (INT64)ReturnCode));
 149     }
 150   }
 151 }
 152
 153 VOID
 154 XenGrantTableDeinit (
 155   XENBUS_DEVICE *Dev
 156   )
 157 {
 158   INTN ReturnCode, Index;
 159   xen_remove_from_physmap_t Parameters;
 160
 161   if (GrantTable == NULL) {
 162     return;
 163   }
 164
 165   for (Index = NR_GRANT_FRAMES - 1; Index >= 0; Index--) {
 166     Parameters.domid = DOMID_SELF;
 167     Parameters.gpfn = (xen_pfn_t) ((UINTN) GrantTable >> EFI_PAGE_SHIFT) + Index;
 168     DEBUG ((EFI_D_INFO, "Xen GrantTable, removing %Lx\n",
 169       (UINT64)Parameters.gpfn));
 170     ReturnCode = XenHypercallMemoryOp (XENMEM_remove_from_physmap, &Parameters);
 171     if (ReturnCode != 0) {
 172       DEBUG ((EFI_D_ERROR,
 173         "Xen GrantTable, remove_from_physmap hypercall error: %Ld\n",
 174         (INT64)ReturnCode));
 175     }
 176   }
 177   GrantTable = NULL;
 178 }
 179
 180 EFI_STATUS
 181 EFIAPI
 182 XenBusGrantAccess (
 183   IN  XENBUS_PROTOCOL *This,
 184   IN  domid_t         DomainId,
 185   IN  UINTN           Frame, // MFN
 186   IN  BOOLEAN         ReadOnly,
 187   OUT grant_ref_t     *RefPtr
 188   )
 189 {
 190   *RefPtr = XenGrantTableGrantAccess (DomainId, Frame, ReadOnly);
 191   return EFI_SUCCESS;
 192 }
 193
 194 EFI_STATUS
 195 EFIAPI
 196 XenBusGrantEndAccess (
 197   IN XENBUS_PROTOCOL  *This,
 198   IN grant_ref_t      Ref
 199   )
 200 {
 201   return XenGrantTableEndAccess (Ref);
 202 }