include/xen/interface/grant_table.h

   1 /******************************************************************************
   2  * grant_table.h
   3  *
   4  * Interface for granting foreign access to page frames, and receiving
   5  * page-ownership transfers.
   6  *
   7  * Permission is hereby granted, free of charge, to any person obtaining a copy
   8  * of this software and associated documentation files (the "Software"), to
   9  * deal in the Software without restriction, including without limitation the
  10  * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
  11  * sell copies of the Software, and to permit persons to whom the Software is
  12  * furnished to do so, subject to the following conditions:
  13  *
  14  * The above copyright notice and this permission notice shall be included in
  15  * all copies or substantial portions of the Software.
  16  *
  17  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  18  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  19  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  20  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  21  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  22  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
  23  * DEALINGS IN THE SOFTWARE.
  24  *
  25  * Copyright (c) 2004, K A Fraser
  26  */
  27
  28 #ifndef __XEN_PUBLIC_GRANT_TABLE_H__
  29 #define __XEN_PUBLIC_GRANT_TABLE_H__
  30
  31
  32 /***********************************
  33  * GRANT TABLE REPRESENTATION
  34  */
  35
  36 /* Some rough guidelines on accessing and updating grant-table entries
  37  * in a concurrency-safe manner. For more information, Linux contains a
  38  * reference implementation for guest OSes (arch/xen/kernel/grant_table.c).
  39  *
  40  * NB. WMB is a no-op on current-generation x86 processors. However, a
  41  *     compiler barrier will still be required.
  42  *
  43  * Introducing a valid entry into the grant table:
  44  *  1. Write ent->domid.
  45  *  2. Write ent->frame:
  46  *      GTF_permit_access:   Frame to which access is permitted.
  47  *      GTF_accept_transfer: Pseudo-phys frame slot being filled by new
  48  *                           frame, or zero if none.
  49  *  3. Write memory barrier (WMB).
  50  *  4. Write ent->flags, inc. valid type.
  51  *
  52  * Invalidating an unused GTF_permit_access entry:
  53  *  1. flags = ent->flags.
  54  *  2. Observe that !(flags & (GTF_reading|GTF_writing)).
  55  *  3. Check result of SMP-safe CMPXCHG(&ent->flags, flags, 0).
  56  *  NB. No need for WMB as reuse of entry is control-dependent on success of
  57  *      step 3, and all architectures guarantee ordering of ctrl-dep writes.
  58  *
  59  * Invalidating an in-use GTF_permit_access entry:
  60  *  This cannot be done directly. Request assistance from the domain controller
  61  *  which can set a timeout on the use of a grant entry and take necessary
  62  *  action. (NB. This is not yet implemented!).
  63  *
  64  * Invalidating an unused GTF_accept_transfer entry:
  65  *  1. flags = ent->flags.
  66  *  2. Observe that !(flags & GTF_transfer_committed). [*]
  67  *  3. Check result of SMP-safe CMPXCHG(&ent->flags, flags, 0).
  68  *  NB. No need for WMB as reuse of entry is control-dependent on success of
  69  *      step 3, and all architectures guarantee ordering of ctrl-dep writes.
  70  *  [*] If GTF_transfer_committed is set then the grant entry is 'committed'.
  71  *      The guest must /not/ modify the grant entry until the address of the
  72  *      transferred frame is written. It is safe for the guest to spin waiting
  73  *      for this to occur (detect by observing GTF_transfer_completed in
  74  *      ent->flags).
  75  *
  76  * Invalidating a committed GTF_accept_transfer entry:
  77  *  1. Wait for (ent->flags & GTF_transfer_completed).
  78  *
  79  * Changing a GTF_permit_access from writable to read-only:
  80  *  Use SMP-safe CMPXCHG to set GTF_readonly, while checking !GTF_writing.
  81  *
  82  * Changing a GTF_permit_access from read-only to writable:
  83  *  Use SMP-safe bit-setting instruction.
  84  */
  85
  86 /*
  87  * A grant table comprises a packed array of grant entries in one or more
  88  * page frames shared between Xen and a guest.
  89  * [XEN]: This field is written by Xen and read by the sharing guest.
  90  * [GST]: This field is written by the guest and read by Xen.
  91  */
  92 struct grant_entry {
  93     /* GTF_xxx: various type and flag information.  [XEN,GST] */
  94     uint16_t flags;
  95     /* The domain being granted foreign privileges. [GST] */
  96     domid_t  domid;
  97     /*
  98      * GTF_permit_access: Frame that @domid is allowed to map and access. [GST]
  99      * GTF_accept_transfer: Frame whose ownership transferred by @domid. [XEN]
 100      */
 101     uint32_t frame;
 102 };
 103
 104 /*
 105  * Type of grant entry.
 106  *  GTF_invalid: This grant entry grants no privileges.
 107  *  GTF_permit_access: Allow @domid to map/access @frame.
 108  *  GTF_accept_transfer: Allow @domid to transfer ownership of one page frame
 109  *                       to this guest. Xen writes the page number to @frame.
 110  */
 111 #define GTF_invalid         (0U<<0)
 112 #define GTF_permit_access   (1U<<0)
 113 #define GTF_accept_transfer (2U<<0)
 114 #define GTF_type_mask       (3U<<0)
 115
 116 /*
 117  * Subflags for GTF_permit_access.
 118  *  GTF_readonly: Restrict @domid to read-only mappings and accesses. [GST]
 119  *  GTF_reading: Grant entry is currently mapped for reading by @domid. [XEN]
 120  *  GTF_writing: Grant entry is currently mapped for writing by @domid. [XEN]
 121  */
 122 #define _GTF_readonly       (2)
 123 #define GTF_readonly        (1U<<_GTF_readonly)
 124 #define _GTF_reading        (3)
 125 #define GTF_reading         (1U<<_GTF_reading)
 126 #define _GTF_writing        (4)
 127 #define GTF_writing         (1U<<_GTF_writing)
 128
 129 /*
 130  * Subflags for GTF_accept_transfer:
 131  *  GTF_transfer_committed: Xen sets this flag to indicate that it is committed
 132  *      to transferring ownership of a page frame. When a guest sees this flag
 133  *      it must /not/ modify the grant entry until GTF_transfer_completed is
 134  *      set by Xen.
 135  *  GTF_transfer_completed: It is safe for the guest to spin-wait on this flag
 136  *      after reading GTF_transfer_committed. Xen will always write the frame
 137  *      address, followed by ORing this flag, in a timely manner.
 138  */
 139 #define _GTF_transfer_committed (2)
 140 #define GTF_transfer_committed  (1U<<_GTF_transfer_committed)
 141 #define _GTF_transfer_completed (3)
 142 #define GTF_transfer_completed  (1U<<_GTF_transfer_completed)
 143
 144
 145 /***********************************
 146  * GRANT TABLE QUERIES AND USES
 147  */
 148
 149 /*
 150  * Reference to a grant entry in a specified domain's grant table.
 151  */
 152 typedef uint32_t grant_ref_t;
 153
 154 /*
 155  * Handle to track a mapping created via a grant reference.
 156  */
 157 typedef uint32_t grant_handle_t;
 158
 159 /*
 160  * GNTTABOP_map_grant_ref: Map the grant entry (<dom>,<ref>) for access
 161  * by devices and/or host CPUs. If successful, <handle> is a tracking number
 162  * that must be presented later to destroy the mapping(s). On error, <handle>
 163  * is a negative status code.
 164  * NOTES:
 165  *  1. If GNTMAP_device_map is specified then <dev_bus_addr> is the address
 166  *     via which I/O devices may access the granted frame.
 167  *  2. If GNTMAP_host_map is specified then a mapping will be added at
 168  *     either a host virtual address in the current address space, or at
 169  *     a PTE at the specified machine address.  The type of mapping to
 170  *     perform is selected through the GNTMAP_contains_pte flag, and the
 171  *     address is specified in <host_addr>.
 172  *  3. Mappings should only be destroyed via GNTTABOP_unmap_grant_ref. If a
 173  *     host mapping is destroyed by other means then it is *NOT* guaranteed
 174  *     to be accounted to the correct grant reference!
 175  */
 176 #define GNTTABOP_map_grant_ref        0
 177 struct gnttab_map_grant_ref {
 178     /* IN parameters. */
 179     uint64_t host_addr;
 180     uint32_t flags;               /* GNTMAP_* */
 181     grant_ref_t ref;
 182     domid_t  dom;
 183     /* OUT parameters. */
 184     int16_t  status;              /* GNTST_* */
 185     grant_handle_t handle;
 186     uint64_t dev_bus_addr;
 187 };
 188
 189 /*
 190  * GNTTABOP_unmap_grant_ref: Destroy one or more grant-reference mappings
 191  * tracked by <handle>. If <host_addr> or <dev_bus_addr> is zero, that
 192  * field is ignored. If non-zero, they must refer to a device/host mapping
 193  * that is tracked by <handle>
 194  * NOTES:
 195  *  1. The call may fail in an undefined manner if either mapping is not
 196  *     tracked by <handle>.
 197  *  3. After executing a batch of unmaps, it is guaranteed that no stale
 198  *     mappings will remain in the device or host TLBs.
 199  */
 200 #define GNTTABOP_unmap_grant_ref      1
 201 struct gnttab_unmap_grant_ref {
 202     /* IN parameters. */
 203     uint64_t host_addr;
 204     uint64_t dev_bus_addr;
 205     grant_handle_t handle;
 206     /* OUT parameters. */
 207     int16_t  status;              /* GNTST_* */
 208 };
 209
 210 /*
 211  * GNTTABOP_setup_table: Set up a grant table for <dom> comprising at least
 212  * <nr_frames> pages. The frame addresses are written to the <frame_list>.
 213  * Only <nr_frames> addresses are written, even if the table is larger.
 214  * NOTES:
 215  *  1. <dom> may be specified as DOMID_SELF.
 216  *  2. Only a sufficiently-privileged domain may specify <dom> != DOMID_SELF.
 217  *  3. Xen may not support more than a single grant-table page per domain.
 218  */
 219 #define GNTTABOP_setup_table          2
 220 struct gnttab_setup_table {
 221     /* IN parameters. */
 222     domid_t  dom;
 223     uint32_t nr_frames;
 224     /* OUT parameters. */
 225     int16_t  status;              /* GNTST_* */
 226     ulong *frame_list;
 227 };
 228
 229 /*
 230  * GNTTABOP_dump_table: Dump the contents of the grant table to the
 231  * xen console. Debugging use only.
 232  */
 233 #define GNTTABOP_dump_table           3
 234 struct gnttab_dump_table {
 235     /* IN parameters. */
 236     domid_t dom;
 237     /* OUT parameters. */
 238     int16_t status;               /* GNTST_* */
 239 };
 240
 241 /*
 242  * GNTTABOP_transfer_grant_ref: Transfer <frame> to a foreign domain. The
 243  * foreign domain has previously registered its interest in the transfer via
 244  * <domid, ref>.
 245  *
 246  * Note that, even if the transfer fails, the specified page no longer belongs
 247  * to the calling domain *unless* the error is GNTST_bad_page.
 248  */
 249 #define GNTTABOP_transfer                4
 250 struct gnttab_transfer {
 251     /* IN parameters. */
 252     unsigned long mfn;
 253     domid_t       domid;
 254     grant_ref_t   ref;
 255     /* OUT parameters. */
 256     int16_t       status;
 257 };
 258
 259
 260 /*
 261  * GNTTABOP_copy: Hypervisor based copy
 262  * source and destinations can be eithers MFNs or, for foreign domains,
 263  * grant references. the foreign domain has to grant read/write access
 264  * in its grant table.
 265  *
 266  * The flags specify what type source and destinations are (either MFN
 267  * or grant reference).
 268  *
 269  * Note that this can also be used to copy data between two domains
 270  * via a third party if the source and destination domains had previously
 271  * grant appropriate access to their pages to the third party.
 272  *
 273  * source_offset specifies an offset in the source frame, dest_offset
 274  * the offset in the target frame and  len specifies the number of
 275  * bytes to be copied.
 276  */
 277
 278 #define _GNTCOPY_source_gref      (0)
 279 #define GNTCOPY_source_gref       (1<<_GNTCOPY_source_gref)
 280 #define _GNTCOPY_dest_gref        (1)
 281 #define GNTCOPY_dest_gref         (1<<_GNTCOPY_dest_gref)
 282
 283 #define GNTTABOP_copy                 5
 284 struct gnttab_copy {
 285         /* IN parameters. */
 286         struct {
 287                 union {
 288                         grant_ref_t ref;
 289                         unsigned long   gmfn;
 290                 } u;
 291                 domid_t  domid;
 292                 uint16_t offset;
 293         } source, dest;
 294         uint16_t      len;
 295         uint16_t      flags;          /* GNTCOPY_* */
 296         /* OUT parameters. */
 297         int16_t       status;
 298 };
 299
 300 /*
 301  * GNTTABOP_query_size: Query the current and maximum sizes of the shared
 302  * grant table.
 303  * NOTES:
 304  *  1. <dom> may be specified as DOMID_SELF.
 305  *  2. Only a sufficiently-privileged domain may specify <dom> != DOMID_SELF.
 306  */
 307 #define GNTTABOP_query_size           6
 308 struct gnttab_query_size {
 309     /* IN parameters. */
 310     domid_t  dom;
 311     /* OUT parameters. */
 312     uint32_t nr_frames;
 313     uint32_t max_nr_frames;
 314     int16_t  status;              /* GNTST_* */
 315 };
 316
 317
 318 /*
 319  * Bitfield values for update_pin_status.flags.
 320  */
 321  /* Map the grant entry for access by I/O devices. */
 322 #define _GNTMAP_device_map      (0)
 323 #define GNTMAP_device_map       (1<<_GNTMAP_device_map)
 324  /* Map the grant entry for access by host CPUs. */
 325 #define _GNTMAP_host_map        (1)
 326 #define GNTMAP_host_map         (1<<_GNTMAP_host_map)
 327  /* Accesses to the granted frame will be restricted to read-only access. */
 328 #define _GNTMAP_readonly        (2)
 329 #define GNTMAP_readonly         (1<<_GNTMAP_readonly)
 330  /*
 331   * GNTMAP_host_map subflag:
 332   *  0 => The host mapping is usable only by the guest OS.
 333   *  1 => The host mapping is usable by guest OS + current application.
 334   */
 335 #define _GNTMAP_application_map (3)
 336 #define GNTMAP_application_map  (1<<_GNTMAP_application_map)
 337
 338  /*
 339   * GNTMAP_contains_pte subflag:
 340   *  0 => This map request contains a host virtual address.
 341   *  1 => This map request contains the machine addess of the PTE to update.
 342   */
 343 #define _GNTMAP_contains_pte    (4)
 344 #define GNTMAP_contains_pte     (1<<_GNTMAP_contains_pte)
 345
 346 /*
 347  * Values for error status returns. All errors are -ve.
 348  */
 349 #define GNTST_okay             (0)  /* Normal return.                        */
 350 #define GNTST_general_error    (-1) /* General undefined error.              */
 351 #define GNTST_bad_domain       (-2) /* Unrecognsed domain id.                */
 352 #define GNTST_bad_gntref       (-3) /* Unrecognised or inappropriate gntref. */
 353 #define GNTST_bad_handle       (-4) /* Unrecognised or inappropriate handle. */
 354 #define GNTST_bad_virt_addr    (-5) /* Inappropriate virtual address to map. */
 355 #define GNTST_bad_dev_addr     (-6) /* Inappropriate device address to unmap.*/
 356 #define GNTST_no_device_space  (-7) /* Out of space in I/O MMU.              */
 357 #define GNTST_permission_denied (-8) /* Not enough privilege for operation.  */
 358 #define GNTST_bad_page         (-9) /* Specified page was invalid for op.    */
 359 #define GNTST_bad_copy_arg    (-10) /* copy arguments cross page boundary */
 360
 361 #define GNTTABOP_error_msgs {                   \
 362     "okay",                                     \
 363     "undefined error",                          \
 364     "unrecognised domain id",                   \
 365     "invalid grant reference",                  \
 366     "invalid mapping handle",                   \
 367     "invalid virtual address",                  \
 368     "invalid device address",                   \
 369     "no spare translation slot in the I/O MMU", \
 370     "permission denied",                        \
 371     "bad page",                                 \
 372     "copy arguments cross page boundary"        \
 373 }
 374
 375 #endif /* __XEN_PUBLIC_GRANT_TABLE_H__ */