OvmfPkg/Include/IndustryStandard/Xen/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  * SPDX-License-Identifier: MIT
   8  *
   9  * Copyright (c) 2004, K A Fraser
  10  */
  11
  12 #ifndef __XEN_PUBLIC_GRANT_TABLE_H__
  13 #define __XEN_PUBLIC_GRANT_TABLE_H__
  14
  15 #include "xen.h"
  16
  17 /*
  18  * `incontents 150 gnttab Grant Tables
  19  *
  20  * Xen's grant tables provide a generic mechanism to memory sharing
  21  * between domains. This shared memory interface underpins the split
  22  * device drivers for block and network IO.
  23  *
  24  * Each domain has its own grant table. This is a data structure that
  25  * is shared with Xen; it allows the domain to tell Xen what kind of
  26  * permissions other domains have on its pages. Entries in the grant
  27  * table are identified by grant references. A grant reference is an
  28  * integer, which indexes into the grant table. It acts as a
  29  * capability which the grantee can use to perform operations on the
  30  * granter's memory.
  31  *
  32  * This capability-based system allows shared-memory communications
  33  * between unprivileged domains. A grant reference also encapsulates
  34  * the details of a shared page, removing the need for a domain to
  35  * know the real machine address of a page it is sharing. This makes
  36  * it possible to share memory correctly with domains running in
  37  * fully virtualised memory.
  38  */
  39
  40 /***********************************
  41  * GRANT TABLE REPRESENTATION
  42  */
  43
  44 /* Some rough guidelines on accessing and updating grant-table entries
  45  * in a concurrency-safe manner. For more information, Linux contains a
  46  * reference implementation for guest OSes (drivers/xen/grant_table.c, see
  47  * http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=blob;f=drivers/xen/grant-table.c;hb=HEAD
  48  *
  49  * NB. WMB is a no-op on current-generation x86 processors. However, a
  50  *     compiler barrier will still be required.
  51  *
  52  * Introducing a valid entry into the grant table:
  53  *  1. Write ent->domid.
  54  *  2. Write ent->frame:
  55  *      GTF_permit_access:   Frame to which access is permitted.
  56  *      GTF_accept_transfer: Pseudo-phys frame slot being filled by new
  57  *                           frame, or zero if none.
  58  *  3. Write memory barrier (WMB).
  59  *  4. Write ent->flags, inc. valid type.
  60  *
  61  * Invalidating an unused GTF_permit_access entry:
  62  *  1. flags = ent->flags.
  63  *  2. Observe that !(flags & (GTF_reading|GTF_writing)).
  64  *  3. Check result of SMP-safe CMPXCHG(&ent->flags, flags, 0).
  65  *  NB. No need for WMB as reuse of entry is control-dependent on success of
  66  *      step 3, and all architectures guarantee ordering of ctrl-dep writes.
  67  *
  68  * Invalidating an in-use GTF_permit_access entry:
  69  *  This cannot be done directly. Request assistance from the domain controller
  70  *  which can set a timeout on the use of a grant entry and take necessary
  71  *  action. (NB. This is not yet implemented!).
  72  *
  73  * Invalidating an unused GTF_accept_transfer entry:
  74  *  1. flags = ent->flags.
  75  *  2. Observe that !(flags & GTF_transfer_committed). [*]
  76  *  3. Check result of SMP-safe CMPXCHG(&ent->flags, flags, 0).
  77  *  NB. No need for WMB as reuse of entry is control-dependent on success of
  78  *      step 3, and all architectures guarantee ordering of ctrl-dep writes.
  79  *  [*] If GTF_transfer_committed is set then the grant entry is 'committed'.
  80  *      The guest must /not/ modify the grant entry until the address of the
  81  *      transferred frame is written. It is safe for the guest to spin waiting
  82  *      for this to occur (detect by observing GTF_transfer_completed in
  83  *      ent->flags).
  84  *
  85  * Invalidating a committed GTF_accept_transfer entry:
  86  *  1. Wait for (ent->flags & GTF_transfer_completed).
  87  *
  88  * Changing a GTF_permit_access from writable to read-only:
  89  *  Use SMP-safe CMPXCHG to set GTF_readonly, while checking !GTF_writing.
  90  *
  91  * Changing a GTF_permit_access from read-only to writable:
  92  *  Use SMP-safe bit-setting instruction.
  93  */
  94
  95 /*
  96  * Reference to a grant entry in a specified domain's grant table.
  97  */
  98 typedef UINT32 grant_ref_t;
  99
 100 /*
 101  * A grant table comprises a packed array of grant entries in one or more
 102  * page frames shared between Xen and a guest.
 103  * [XEN]: This field is written by Xen and read by the sharing guest.
 104  * [GST]: This field is written by the guest and read by Xen.
 105  */
 106
 107 /*
 108  * Version 1 of the grant table entry structure is maintained purely
 109  * for backwards compatibility.  New guests should use version 2.
 110  */
 111 #if __XEN_INTERFACE_VERSION__ < 0x0003020a
 112 #define grant_entry_v1 grant_entry
 113 #define grant_entry_v1_t grant_entry_t
 114 #endif
 115 struct grant_entry_v1 {
 116     /* GTF_xxx: various type and flag information.  [XEN,GST] */
 117     UINT16 flags;
 118     /* The domain being granted foreign privileges. [GST] */
 119     domid_t  domid;
 120     /*
 121      * GTF_permit_access: Frame that @domid is allowed to map and access. [GST]
 122      * GTF_accept_transfer: Frame whose ownership transferred by @domid. [XEN]
 123      */
 124     UINT32 frame;
 125 };
 126 typedef struct grant_entry_v1 grant_entry_v1_t;
 127
 128 /* The first few grant table entries will be preserved across grant table
 129  * version changes and may be pre-populated at domain creation by tools.
 130  */
 131 #define GNTTAB_NR_RESERVED_ENTRIES     8
 132 #define GNTTAB_RESERVED_CONSOLE        0
 133 #define GNTTAB_RESERVED_XENSTORE       1
 134
 135 /*
 136  * Type of grant entry.
 137  *  GTF_invalid: This grant entry grants no privileges.
 138  *  GTF_permit_access: Allow @domid to map/access @frame.
 139  *  GTF_accept_transfer: Allow @domid to transfer ownership of one page frame
 140  *                       to this guest. Xen writes the page number to @frame.
 141  *  GTF_transitive: Allow @domid to transitively access a subrange of
 142  *                  @trans_grant in @trans_domid.  No mappings are allowed.
 143  */
 144 #define GTF_invalid         (0U<<0)
 145 #define GTF_permit_access   (1U<<0)
 146 #define GTF_accept_transfer (2U<<0)
 147 #define GTF_transitive      (3U<<0)
 148 #define GTF_type_mask       (3U<<0)
 149
 150 /*
 151  * Subflags for GTF_permit_access.
 152  *  GTF_readonly: Restrict @domid to read-only mappings and accesses. [GST]
 153  *  GTF_reading: Grant entry is currently mapped for reading by @domid. [XEN]
 154  *  GTF_writing: Grant entry is currently mapped for writing by @domid. [XEN]
 155  *  GTF_PAT, GTF_PWT, GTF_PCD: (x86) cache attribute flags for the grant [GST]
 156  *  GTF_sub_page: Grant access to only a subrange of the page.  @domid
 157  *                will only be allowed to copy from the grant, and not
 158  *                map it. [GST]
 159  */
 160 #define _GTF_readonly       (2)
 161 #define GTF_readonly        (1U<<_GTF_readonly)
 162 #define _GTF_reading        (3)
 163 #define GTF_reading         (1U<<_GTF_reading)
 164 #define _GTF_writing        (4)
 165 #define GTF_writing         (1U<<_GTF_writing)
 166 #define _GTF_PWT            (5)
 167 #define GTF_PWT             (1U<<_GTF_PWT)
 168 #define _GTF_PCD            (6)
 169 #define GTF_PCD             (1U<<_GTF_PCD)
 170 #define _GTF_PAT            (7)
 171 #define GTF_PAT             (1U<<_GTF_PAT)
 172 #define _GTF_sub_page       (8)
 173 #define GTF_sub_page        (1U<<_GTF_sub_page)
 174
 175 /*
 176  * Subflags for GTF_accept_transfer:
 177  *  GTF_transfer_committed: Xen sets this flag to indicate that it is committed
 178  *      to transferring ownership of a page frame. When a guest sees this flag
 179  *      it must /not/ modify the grant entry until GTF_transfer_completed is
 180  *      set by Xen.
 181  *  GTF_transfer_completed: It is safe for the guest to spin-wait on this flag
 182  *      after reading GTF_transfer_committed. Xen will always write the frame
 183  *      address, followed by ORing this flag, in a timely manner.
 184  */
 185 #define _GTF_transfer_committed (2)
 186 #define GTF_transfer_committed  (1U<<_GTF_transfer_committed)
 187 #define _GTF_transfer_completed (3)
 188 #define GTF_transfer_completed  (1U<<_GTF_transfer_completed)
 189
 190 /*
 191  * Version 2 grant table entries.  These fulfil the same role as
 192  * version 1 entries, but can represent more complicated operations.
 193  * Any given domain will have either a version 1 or a version 2 table,
 194  * and every entry in the table will be the same version.
 195  *
 196  * The interface by which domains use grant references does not depend
 197  * on the grant table version in use by the other domain.
 198  */
 199 #if __XEN_INTERFACE_VERSION__ >= 0x0003020a
 200 /*
 201  * Version 1 and version 2 grant entries share a common prefix.  The
 202  * fields of the prefix are documented as part of struct
 203  * grant_entry_v1.
 204  */
 205 struct grant_entry_header {
 206     UINT16 flags;
 207     domid_t  domid;
 208 };
 209 typedef struct grant_entry_header grant_entry_header_t;
 210
 211 /*
 212  * Version 2 of the grant entry structure.
 213  */
 214 union grant_entry_v2 {
 215     grant_entry_header_t hdr;
 216
 217     /*
 218      * This member is used for V1-style full page grants, where either:
 219      *
 220      * -- hdr.type is GTF_accept_transfer, or
 221      * -- hdr.type is GTF_permit_access and GTF_sub_page is not set.
 222      *
 223      * In that case, the frame field has the same semantics as the
 224      * field of the same name in the V1 entry structure.
 225      */
 226     struct {
 227         grant_entry_header_t hdr;
 228         UINT32 pad0;
 229         UINT64 frame;
 230     } full_page;
 231
 232     /*
 233      * If the grant type is GTF_grant_access and GTF_sub_page is set,
 234      * @domid is allowed to access bytes [@page_off,@page_off+@length)
 235      * in frame @frame.
 236      */
 237     struct {
 238         grant_entry_header_t hdr;
 239         UINT16 page_off;
 240         UINT16 length;
 241         UINT64 frame;
 242     } sub_page;
 243
 244     /*
 245      * If the grant is GTF_transitive, @domid is allowed to use the
 246      * grant @gref in domain @trans_domid, as if it was the local
 247      * domain.  Obviously, the transitive access must be compatible
 248      * with the original grant.
 249      *
 250      * The current version of Xen does not allow transitive grants
 251      * to be mapped.
 252      */
 253     struct {
 254         grant_entry_header_t hdr;
 255         domid_t trans_domid;
 256         UINT16 pad0;
 257         grant_ref_t gref;
 258     } transitive;
 259
 260     UINT32 __spacer[4]; /* Pad to a power of two */
 261 };
 262 typedef union grant_entry_v2 grant_entry_v2_t;
 263
 264 typedef UINT16 grant_status_t;
 265
 266 #endif /* __XEN_INTERFACE_VERSION__ */
 267
 268 /***********************************
 269  * GRANT TABLE QUERIES AND USES
 270  */
 271
 272 /* ` enum neg_errnoval
 273  * ` HYPERVISOR_grant_table_op(enum grant_table_op cmd,
 274  * `                           VOID *args,
 275  * `                           UINT32 count)
 276  * `
 277  *
 278  * @args points to an array of a per-command data structure. The array
 279  * has @count members
 280  */
 281
 282 /* ` enum grant_table_op { // GNTTABOP_* => struct gnttab_* */
 283 #define GNTTABOP_map_grant_ref        0
 284 #define GNTTABOP_unmap_grant_ref      1
 285 /* ` } */
 286
 287 /*
 288  * Handle to track a mapping created via a grant reference.
 289  */
 290 typedef UINT32 grant_handle_t;
 291
 292 /*
 293  * GNTTABOP_map_grant_ref: Map the grant entry (<dom>,<ref>) for access
 294  * by devices and/or host CPUs. If successful, <handle> is a tracking number
 295  * that must be presented later to destroy the mapping(s). On error, <handle>
 296  * is a negative status code.
 297  * NOTES:
 298  *  1. If GNTMAP_device_map is specified then <dev_bus_addr> is the address
 299  *     via which I/O devices may access the granted frame.
 300  *  2. If GNTMAP_host_map is specified then a mapping will be added at
 301  *     either a host virtual address in the current address space, or at
 302  *     a PTE at the specified machine address.  The type of mapping to
 303  *     perform is selected through the GNTMAP_contains_pte flag, and the
 304  *     address is specified in <host_addr>.
 305  *  3. Mappings should only be destroyed via GNTTABOP_unmap_grant_ref. If a
 306  *     host mapping is destroyed by other means then it is *NOT* guaranteed
 307  *     to be accounted to the correct grant reference!
 308  */
 309 struct gnttab_map_grant_ref {
 310     /* IN parameters. */
 311     UINT64 host_addr;
 312     UINT32 flags;               /* GNTMAP_* */
 313     grant_ref_t ref;
 314     domid_t  dom;
 315     /* OUT parameters. */
 316     INT16  status;              /* => enum grant_status */
 317     grant_handle_t handle;
 318     UINT64 dev_bus_addr;
 319 };
 320 typedef struct gnttab_map_grant_ref gnttab_map_grant_ref_t;
 321 DEFINE_XEN_GUEST_HANDLE(gnttab_map_grant_ref_t);
 322
 323 /*
 324  * GNTTABOP_unmap_grant_ref: Destroy one or more grant-reference mappings
 325  * tracked by <handle>. If <host_addr> or <dev_bus_addr> is zero, that
 326  * field is ignored. If non-zero, they must refer to a device/host mapping
 327  * that is tracked by <handle>
 328  * NOTES:
 329  *  1. The call may fail in an undefined manner if either mapping is not
 330  *     tracked by <handle>.
 331  *  3. After executing a batch of unmaps, it is guaranteed that no stale
 332  *     mappings will remain in the device or host TLBs.
 333  */
 334 struct gnttab_unmap_grant_ref {
 335     /* IN parameters. */
 336     UINT64 host_addr;
 337     UINT64 dev_bus_addr;
 338     grant_handle_t handle;
 339     /* OUT parameters. */
 340     INT16  status;              /* => enum grant_status */
 341 };
 342 typedef struct gnttab_unmap_grant_ref gnttab_unmap_grant_ref_t;
 343 DEFINE_XEN_GUEST_HANDLE(gnttab_unmap_grant_ref_t);
 344
 345 /*
 346  * Bitfield values for gnttab_map_grant_ref.flags.
 347  */
 348  /* Map the grant entry for access by I/O devices. */
 349 #define _GNTMAP_device_map      (0)
 350 #define GNTMAP_device_map       (1<<_GNTMAP_device_map)
 351  /* Map the grant entry for access by host CPUs. */
 352 #define _GNTMAP_host_map        (1)
 353 #define GNTMAP_host_map         (1<<_GNTMAP_host_map)
 354  /* Accesses to the granted frame will be restricted to read-only access. */
 355 #define _GNTMAP_readonly        (2)
 356 #define GNTMAP_readonly         (1<<_GNTMAP_readonly)
 357  /*
 358   * GNTMAP_host_map subflag:
 359   *  0 => The host mapping is usable only by the guest OS.
 360   *  1 => The host mapping is usable by guest OS + current application.
 361   */
 362 #define _GNTMAP_application_map (3)
 363 #define GNTMAP_application_map  (1<<_GNTMAP_application_map)
 364
 365  /*
 366   * GNTMAP_contains_pte subflag:
 367   *  0 => This map request contains a host virtual address.
 368   *  1 => This map request contains the machine addess of the PTE to update.
 369   */
 370 #define _GNTMAP_contains_pte    (4)
 371 #define GNTMAP_contains_pte     (1<<_GNTMAP_contains_pte)
 372
 373 #define _GNTMAP_can_fail        (5)
 374 #define GNTMAP_can_fail         (1<<_GNTMAP_can_fail)
 375
 376 /*
 377  * Bits to be placed in guest kernel available PTE bits (architecture
 378  * dependent; only supported when XENFEAT_gnttab_map_avail_bits is set).
 379  */
 380 #define _GNTMAP_guest_avail0    (16)
 381 #define GNTMAP_guest_avail_mask ((UINT32)~0 << _GNTMAP_guest_avail0)
 382
 383 /*
 384  * Values for error status returns. All errors are -ve.
 385  */
 386 /* ` enum grant_status { */
 387 #define GNTST_okay             (0)  /* Normal return.                        */
 388 #define GNTST_general_error    (-1) /* General undefined error.              */
 389 #define GNTST_bad_domain       (-2) /* Unrecognsed domain id.                */
 390 #define GNTST_bad_gntref       (-3) /* Unrecognised or inappropriate gntref. */
 391 #define GNTST_bad_handle       (-4) /* Unrecognised or inappropriate handle. */
 392 #define GNTST_bad_virt_addr    (-5) /* Inappropriate virtual address to map. */
 393 #define GNTST_bad_dev_addr     (-6) /* Inappropriate device address to unmap.*/
 394 #define GNTST_no_device_space  (-7) /* Out of space in I/O MMU.              */
 395 #define GNTST_permission_denied (-8) /* Not enough privilege for operation.  */
 396 #define GNTST_bad_page         (-9) /* Specified page was invalid for op.    */
 397 #define GNTST_bad_copy_arg    (-10) /* copy arguments cross page boundary.   */
 398 #define GNTST_address_too_big (-11) /* transfer page address too large.      */
 399 #define GNTST_eagain          (-12) /* Operation not done; try again.        */
 400 /* ` } */
 401
 402 #define GNTTABOP_error_msgs {                   \
 403     "okay",                                     \
 404     "undefined error",                          \
 405     "unrecognised domain id",                   \
 406     "invalid grant reference",                  \
 407     "invalid mapping handle",                   \
 408     "invalid virtual address",                  \
 409     "invalid device address",                   \
 410     "no spare translation slot in the I/O MMU", \
 411     "permission denied",                        \
 412     "bad page",                                 \
 413     "copy arguments cross page boundary",       \
 414     "page address size too large",              \
 415     "operation not done; try again"             \
 416 }
 417
 418 #endif /* __XEN_PUBLIC_GRANT_TABLE_H__ */
 419
 420 /*
 421  * Local variables:
 422  * mode: C
 423  * c-file-style: "BSD"
 424  * c-basic-offset: 4
 425  * tab-width: 4
 426  * indent-tabs-mode: nil
 427  * End:
 428  */