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 #include <xen/interface/xen.h>
32 
33 /***********************************
34  * GRANT TABLE REPRESENTATION
35  */
36 
37 /* Some rough guidelines on accessing and updating grant-table entries
38  * in a concurrency-safe manner. For more information, Linux contains a
39  * reference implementation for guest OSes (arch/xen/kernel/grant_table.c).
40  *
41  * NB. WMB is a no-op on current-generation x86 processors. However, a
42  *     compiler barrier will still be required.
43  *
44  * Introducing a valid entry into the grant table:
45  *  1. Write ent->domid.
46  *  2. Write ent->frame:
47  *      GTF_permit_access:   Frame to which access is permitted.
48  *      GTF_accept_transfer: Pseudo-phys frame slot being filled by new
49  *                           frame, or zero if none.
50  *  3. Write memory barrier (WMB).
51  *  4. Write ent->flags, inc. valid type.
52  *
53  * Invalidating an unused GTF_permit_access entry:
54  *  1. flags = ent->flags.
55  *  2. Observe that !(flags & (GTF_reading|GTF_writing)).
56  *  3. Check result of SMP-safe CMPXCHG(&ent->flags, flags, 0).
57  *  NB. No need for WMB as reuse of entry is control-dependent on success of
58  *      step 3, and all architectures guarantee ordering of ctrl-dep writes.
59  *
60  * Invalidating an in-use GTF_permit_access entry:
61  *  This cannot be done directly. Request assistance from the domain controller
62  *  which can set a timeout on the use of a grant entry and take necessary
63  *  action. (NB. This is not yet implemented!).
64  *
65  * Invalidating an unused GTF_accept_transfer entry:
66  *  1. flags = ent->flags.
67  *  2. Observe that !(flags & GTF_transfer_committed). [*]
68  *  3. Check result of SMP-safe CMPXCHG(&ent->flags, flags, 0).
69  *  NB. No need for WMB as reuse of entry is control-dependent on success of
70  *      step 3, and all architectures guarantee ordering of ctrl-dep writes.
71  *  [*] If GTF_transfer_committed is set then the grant entry is 'committed'.
72  *      The guest must /not/ modify the grant entry until the address of the
73  *      transferred frame is written. It is safe for the guest to spin waiting
74  *      for this to occur (detect by observing GTF_transfer_completed in
75  *      ent->flags).
76  *
77  * Invalidating a committed GTF_accept_transfer entry:
78  *  1. Wait for (ent->flags & GTF_transfer_completed).
79  *
80  * Changing a GTF_permit_access from writable to read-only:
81  *  Use SMP-safe CMPXCHG to set GTF_readonly, while checking !GTF_writing.
82  *
83  * Changing a GTF_permit_access from read-only to writable:
84  *  Use SMP-safe bit-setting instruction.
85  */
86 
87 /*
88  * Reference to a grant entry in a specified domain's grant table.
89  */
90 typedef uint32_t grant_ref_t;
91 
92 /*
93  * A grant table comprises a packed array of grant entries in one or more
94  * page frames shared between Xen and a guest.
95  * [XEN]: This field is written by Xen and read by the sharing guest.
96  * [GST]: This field is written by the guest and read by Xen.
97  */
98 
99 /*
100  * Version 1 of the grant table entry structure is maintained purely
101  * for backwards compatibility.  New guests should use version 2.
102  */
103 struct grant_entry_v1 {
104     /* GTF_xxx: various type and flag information.  [XEN,GST] */
105     uint16_t flags;
106     /* The domain being granted foreign privileges. [GST] */
107     domid_t  domid;
108     /*
109      * GTF_permit_access: Frame that @domid is allowed to map and access. [GST]
110      * GTF_accept_transfer: Frame whose ownership transferred by @domid. [XEN]
111      */
112     uint32_t frame;
113 };
114 
115 /*
116  * Type of grant entry.
117  *  GTF_invalid: This grant entry grants no privileges.
118  *  GTF_permit_access: Allow @domid to map/access @frame.
119  *  GTF_accept_transfer: Allow @domid to transfer ownership of one page frame
120  *                       to this guest. Xen writes the page number to @frame.
121  *  GTF_transitive: Allow @domid to transitively access a subrange of
122  *                  @trans_grant in @trans_domid.  No mappings are allowed.
123  */
124 #define GTF_invalid         (0U<<0)
125 #define GTF_permit_access   (1U<<0)
126 #define GTF_accept_transfer (2U<<0)
127 #define GTF_transitive      (3U<<0)
128 #define GTF_type_mask       (3U<<0)
129 
130 /*
131  * Subflags for GTF_permit_access.
132  *  GTF_readonly: Restrict @domid to read-only mappings and accesses. [GST]
133  *  GTF_reading: Grant entry is currently mapped for reading by @domid. [XEN]
134  *  GTF_writing: Grant entry is currently mapped for writing by @domid. [XEN]
135  *  GTF_sub_page: Grant access to only a subrange of the page.  @domid
136  *                will only be allowed to copy from the grant, and not
137  *                map it. [GST]
138  */
139 #define _GTF_readonly       (2)
140 #define GTF_readonly        (1U<<_GTF_readonly)
141 #define _GTF_reading        (3)
142 #define GTF_reading         (1U<<_GTF_reading)
143 #define _GTF_writing        (4)
144 #define GTF_writing         (1U<<_GTF_writing)
145 #define _GTF_sub_page       (8)
146 #define GTF_sub_page        (1U<<_GTF_sub_page)
147 
148 /*
149  * Subflags for GTF_accept_transfer:
150  *  GTF_transfer_committed: Xen sets this flag to indicate that it is committed
151  *      to transferring ownership of a page frame. When a guest sees this flag
152  *      it must /not/ modify the grant entry until GTF_transfer_completed is
153  *      set by Xen.
154  *  GTF_transfer_completed: It is safe for the guest to spin-wait on this flag
155  *      after reading GTF_transfer_committed. Xen will always write the frame
156  *      address, followed by ORing this flag, in a timely manner.
157  */
158 #define _GTF_transfer_committed (2)
159 #define GTF_transfer_committed  (1U<<_GTF_transfer_committed)
160 #define _GTF_transfer_completed (3)
161 #define GTF_transfer_completed  (1U<<_GTF_transfer_completed)
162 
163 /*
164  * Version 2 grant table entries.  These fulfil the same role as
165  * version 1 entries, but can represent more complicated operations.
166  * Any given domain will have either a version 1 or a version 2 table,
167  * and every entry in the table will be the same version.
168  *
169  * The interface by which domains use grant references does not depend
170  * on the grant table version in use by the other domain.
171  */
172 
173 /*
174  * Version 1 and version 2 grant entries share a common prefix.  The
175  * fields of the prefix are documented as part of struct
176  * grant_entry_v1.
177  */
178 struct grant_entry_header {
179     uint16_t flags;
180     domid_t  domid;
181 };
182 
183 /*
184  * Version 2 of the grant entry structure, here is an union because three
185  * different types are suppotted: full_page, sub_page and transitive.
186  */
187 union grant_entry_v2 {
188     struct grant_entry_header hdr;
189 
190     /*
191      * This member is used for V1-style full page grants, where either:
192      *
193      * -- hdr.type is GTF_accept_transfer, or
194      * -- hdr.type is GTF_permit_access and GTF_sub_page is not set.
195      *
196      * In that case, the frame field has the same semantics as the
197      * field of the same name in the V1 entry structure.
198      */
199     struct {
200 	struct grant_entry_header hdr;
201 	uint32_t pad0;
202 	uint64_t frame;
203     } full_page;
204 
205     /*
206      * If the grant type is GTF_grant_access and GTF_sub_page is set,
207      * @domid is allowed to access bytes [@page_off,@page_off+@length)
208      * in frame @frame.
209      */
210     struct {
211 	struct grant_entry_header hdr;
212 	uint16_t page_off;
213 	uint16_t length;
214 	uint64_t frame;
215     } sub_page;
216 
217     /*
218      * If the grant is GTF_transitive, @domid is allowed to use the
219      * grant @gref in domain @trans_domid, as if it was the local
220      * domain.  Obviously, the transitive access must be compatible
221      * with the original grant.
222      */
223     struct {
224 	struct grant_entry_header hdr;
225 	domid_t trans_domid;
226 	uint16_t pad0;
227 	grant_ref_t gref;
228     } transitive;
229 
230     uint32_t __spacer[4]; /* Pad to a power of two */
231 };
232 
233 typedef uint16_t grant_status_t;
234 
235 /***********************************
236  * GRANT TABLE QUERIES AND USES
237  */
238 
239 /*
240  * Handle to track a mapping created via a grant reference.
241  */
242 typedef uint32_t grant_handle_t;
243 
244 /*
245  * GNTTABOP_map_grant_ref: Map the grant entry (<dom>,<ref>) for access
246  * by devices and/or host CPUs. If successful, <handle> is a tracking number
247  * that must be presented later to destroy the mapping(s). On error, <handle>
248  * is a negative status code.
249  * NOTES:
250  *  1. If GNTMAP_device_map is specified then <dev_bus_addr> is the address
251  *     via which I/O devices may access the granted frame.
252  *  2. If GNTMAP_host_map is specified then a mapping will be added at
253  *     either a host virtual address in the current address space, or at
254  *     a PTE at the specified machine address.  The type of mapping to
255  *     perform is selected through the GNTMAP_contains_pte flag, and the
256  *     address is specified in <host_addr>.
257  *  3. Mappings should only be destroyed via GNTTABOP_unmap_grant_ref. If a
258  *     host mapping is destroyed by other means then it is *NOT* guaranteed
259  *     to be accounted to the correct grant reference!
260  */
261 #define GNTTABOP_map_grant_ref        0
262 struct gnttab_map_grant_ref {
263     /* IN parameters. */
264     uint64_t host_addr;
265     uint32_t flags;               /* GNTMAP_* */
266     grant_ref_t ref;
267     domid_t  dom;
268     /* OUT parameters. */
269     int16_t  status;              /* GNTST_* */
270     grant_handle_t handle;
271     uint64_t dev_bus_addr;
272 };
273 DEFINE_GUEST_HANDLE_STRUCT(gnttab_map_grant_ref);
274 
275 /*
276  * GNTTABOP_unmap_grant_ref: Destroy one or more grant-reference mappings
277  * tracked by <handle>. If <host_addr> or <dev_bus_addr> is zero, that
278  * field is ignored. If non-zero, they must refer to a device/host mapping
279  * that is tracked by <handle>
280  * NOTES:
281  *  1. The call may fail in an undefined manner if either mapping is not
282  *     tracked by <handle>.
283  *  3. After executing a batch of unmaps, it is guaranteed that no stale
284  *     mappings will remain in the device or host TLBs.
285  */
286 #define GNTTABOP_unmap_grant_ref      1
287 struct gnttab_unmap_grant_ref {
288     /* IN parameters. */
289     uint64_t host_addr;
290     uint64_t dev_bus_addr;
291     grant_handle_t handle;
292     /* OUT parameters. */
293     int16_t  status;              /* GNTST_* */
294 };
295 DEFINE_GUEST_HANDLE_STRUCT(gnttab_unmap_grant_ref);
296 
297 /*
298  * GNTTABOP_setup_table: Set up a grant table for <dom> comprising at least
299  * <nr_frames> pages. The frame addresses are written to the <frame_list>.
300  * Only <nr_frames> addresses are written, even if the table is larger.
301  * NOTES:
302  *  1. <dom> may be specified as DOMID_SELF.
303  *  2. Only a sufficiently-privileged domain may specify <dom> != DOMID_SELF.
304  *  3. Xen may not support more than a single grant-table page per domain.
305  */
306 #define GNTTABOP_setup_table          2
307 struct gnttab_setup_table {
308     /* IN parameters. */
309     domid_t  dom;
310     uint32_t nr_frames;
311     /* OUT parameters. */
312     int16_t  status;              /* GNTST_* */
313     GUEST_HANDLE(xen_pfn_t) frame_list;
314 };
315 DEFINE_GUEST_HANDLE_STRUCT(gnttab_setup_table);
316 
317 /*
318  * GNTTABOP_dump_table: Dump the contents of the grant table to the
319  * xen console. Debugging use only.
320  */
321 #define GNTTABOP_dump_table           3
322 struct gnttab_dump_table {
323     /* IN parameters. */
324     domid_t dom;
325     /* OUT parameters. */
326     int16_t status;               /* GNTST_* */
327 };
328 DEFINE_GUEST_HANDLE_STRUCT(gnttab_dump_table);
329 
330 /*
331  * GNTTABOP_transfer_grant_ref: Transfer <frame> to a foreign domain. The
332  * foreign domain has previously registered its interest in the transfer via
333  * <domid, ref>.
334  *
335  * Note that, even if the transfer fails, the specified page no longer belongs
336  * to the calling domain *unless* the error is GNTST_bad_page.
337  */
338 #define GNTTABOP_transfer                4
339 struct gnttab_transfer {
340     /* IN parameters. */
341     xen_pfn_t mfn;
342     domid_t       domid;
343     grant_ref_t   ref;
344     /* OUT parameters. */
345     int16_t       status;
346 };
347 DEFINE_GUEST_HANDLE_STRUCT(gnttab_transfer);
348 
349 /*
350  * GNTTABOP_copy: Hypervisor based copy
351  * source and destinations can be eithers MFNs or, for foreign domains,
352  * grant references. the foreign domain has to grant read/write access
353  * in its grant table.
354  *
355  * The flags specify what type source and destinations are (either MFN
356  * or grant reference).
357  *
358  * Note that this can also be used to copy data between two domains
359  * via a third party if the source and destination domains had previously
360  * grant appropriate access to their pages to the third party.
361  *
362  * source_offset specifies an offset in the source frame, dest_offset
363  * the offset in the target frame and  len specifies the number of
364  * bytes to be copied.
365  */
366 
367 #define _GNTCOPY_source_gref      (0)
368 #define GNTCOPY_source_gref       (1<<_GNTCOPY_source_gref)
369 #define _GNTCOPY_dest_gref        (1)
370 #define GNTCOPY_dest_gref         (1<<_GNTCOPY_dest_gref)
371 
372 #define GNTTABOP_copy                 5
373 struct gnttab_copy {
374 	/* IN parameters. */
375 	struct {
376 		union {
377 			grant_ref_t ref;
378 			xen_pfn_t   gmfn;
379 		} u;
380 		domid_t  domid;
381 		uint16_t offset;
382 	} source, dest;
383 	uint16_t      len;
384 	uint16_t      flags;          /* GNTCOPY_* */
385 	/* OUT parameters. */
386 	int16_t       status;
387 };
388 DEFINE_GUEST_HANDLE_STRUCT(gnttab_copy);
389 
390 /*
391  * GNTTABOP_query_size: Query the current and maximum sizes of the shared
392  * grant table.
393  * NOTES:
394  *  1. <dom> may be specified as DOMID_SELF.
395  *  2. Only a sufficiently-privileged domain may specify <dom> != DOMID_SELF.
396  */
397 #define GNTTABOP_query_size           6
398 struct gnttab_query_size {
399     /* IN parameters. */
400     domid_t  dom;
401     /* OUT parameters. */
402     uint32_t nr_frames;
403     uint32_t max_nr_frames;
404     int16_t  status;              /* GNTST_* */
405 };
406 DEFINE_GUEST_HANDLE_STRUCT(gnttab_query_size);
407 
408 /*
409  * GNTTABOP_unmap_and_replace: Destroy one or more grant-reference mappings
410  * tracked by <handle> but atomically replace the page table entry with one
411  * pointing to the machine address under <new_addr>.  <new_addr> will be
412  * redirected to the null entry.
413  * NOTES:
414  *  1. The call may fail in an undefined manner if either mapping is not
415  *     tracked by <handle>.
416  *  2. After executing a batch of unmaps, it is guaranteed that no stale
417  *     mappings will remain in the device or host TLBs.
418  */
419 #define GNTTABOP_unmap_and_replace    7
420 struct gnttab_unmap_and_replace {
421     /* IN parameters. */
422     uint64_t host_addr;
423     uint64_t new_addr;
424     grant_handle_t handle;
425     /* OUT parameters. */
426     int16_t  status;              /* GNTST_* */
427 };
428 DEFINE_GUEST_HANDLE_STRUCT(gnttab_unmap_and_replace);
429 
430 /*
431  * GNTTABOP_set_version: Request a particular version of the grant
432  * table shared table structure.  This operation can only be performed
433  * once in any given domain.  It must be performed before any grants
434  * are activated; otherwise, the domain will be stuck with version 1.
435  * The only defined versions are 1 and 2.
436  */
437 #define GNTTABOP_set_version          8
438 struct gnttab_set_version {
439     /* IN parameters */
440     uint32_t version;
441 };
442 DEFINE_GUEST_HANDLE_STRUCT(gnttab_set_version);
443 
444 /*
445  * GNTTABOP_get_status_frames: Get the list of frames used to store grant
446  * status for <dom>. In grant format version 2, the status is separated
447  * from the other shared grant fields to allow more efficient synchronization
448  * using barriers instead of atomic cmpexch operations.
449  * <nr_frames> specify the size of vector <frame_list>.
450  * The frame addresses are returned in the <frame_list>.
451  * Only <nr_frames> addresses are returned, even if the table is larger.
452  * NOTES:
453  *  1. <dom> may be specified as DOMID_SELF.
454  *  2. Only a sufficiently-privileged domain may specify <dom> != DOMID_SELF.
455  */
456 #define GNTTABOP_get_status_frames     9
457 struct gnttab_get_status_frames {
458     /* IN parameters. */
459     uint32_t nr_frames;
460     domid_t  dom;
461     /* OUT parameters. */
462     int16_t  status;              /* GNTST_* */
463     GUEST_HANDLE(uint64_t) frame_list;
464 };
465 DEFINE_GUEST_HANDLE_STRUCT(gnttab_get_status_frames);
466 
467 /*
468  * GNTTABOP_get_version: Get the grant table version which is in
469  * effect for domain <dom>.
470  */
471 #define GNTTABOP_get_version          10
472 struct gnttab_get_version {
473     /* IN parameters */
474     domid_t dom;
475     uint16_t pad;
476     /* OUT parameters */
477     uint32_t version;
478 };
479 DEFINE_GUEST_HANDLE_STRUCT(gnttab_get_version);
480 
481 /*
482  * Issue one or more cache maintenance operations on a portion of a
483  * page granted to the calling domain by a foreign domain.
484  */
485 #define GNTTABOP_cache_flush          12
486 struct gnttab_cache_flush {
487     union {
488         uint64_t dev_bus_addr;
489         grant_ref_t ref;
490     } a;
491     uint16_t offset;   /* offset from start of grant */
492     uint16_t length;   /* size within the grant */
493 #define GNTTAB_CACHE_CLEAN          (1<<0)
494 #define GNTTAB_CACHE_INVAL          (1<<1)
495 #define GNTTAB_CACHE_SOURCE_GREF    (1<<31)
496     uint32_t op;
497 };
498 DEFINE_GUEST_HANDLE_STRUCT(gnttab_cache_flush);
499 
500 /*
501  * Bitfield values for update_pin_status.flags.
502  */
503  /* Map the grant entry for access by I/O devices. */
504 #define _GNTMAP_device_map      (0)
505 #define GNTMAP_device_map       (1<<_GNTMAP_device_map)
506  /* Map the grant entry for access by host CPUs. */
507 #define _GNTMAP_host_map        (1)
508 #define GNTMAP_host_map         (1<<_GNTMAP_host_map)
509  /* Accesses to the granted frame will be restricted to read-only access. */
510 #define _GNTMAP_readonly        (2)
511 #define GNTMAP_readonly         (1<<_GNTMAP_readonly)
512  /*
513   * GNTMAP_host_map subflag:
514   *  0 => The host mapping is usable only by the guest OS.
515   *  1 => The host mapping is usable by guest OS + current application.
516   */
517 #define _GNTMAP_application_map (3)
518 #define GNTMAP_application_map  (1<<_GNTMAP_application_map)
519 
520  /*
521   * GNTMAP_contains_pte subflag:
522   *  0 => This map request contains a host virtual address.
523   *  1 => This map request contains the machine addess of the PTE to update.
524   */
525 #define _GNTMAP_contains_pte    (4)
526 #define GNTMAP_contains_pte     (1<<_GNTMAP_contains_pte)
527 
528 /*
529  * Bits to be placed in guest kernel available PTE bits (architecture
530  * dependent; only supported when XENFEAT_gnttab_map_avail_bits is set).
531  */
532 #define _GNTMAP_guest_avail0    (16)
533 #define GNTMAP_guest_avail_mask ((uint32_t)~0 << _GNTMAP_guest_avail0)
534 
535 /*
536  * Values for error status returns. All errors are -ve.
537  */
538 #define GNTST_okay             (0)  /* Normal return.                        */
539 #define GNTST_general_error    (-1) /* General undefined error.              */
540 #define GNTST_bad_domain       (-2) /* Unrecognsed domain id.                */
541 #define GNTST_bad_gntref       (-3) /* Unrecognised or inappropriate gntref. */
542 #define GNTST_bad_handle       (-4) /* Unrecognised or inappropriate handle. */
543 #define GNTST_bad_virt_addr    (-5) /* Inappropriate virtual address to map. */
544 #define GNTST_bad_dev_addr     (-6) /* Inappropriate device address to unmap.*/
545 #define GNTST_no_device_space  (-7) /* Out of space in I/O MMU.              */
546 #define GNTST_permission_denied (-8) /* Not enough privilege for operation.  */
547 #define GNTST_bad_page         (-9) /* Specified page was invalid for op.    */
548 #define GNTST_bad_copy_arg    (-10) /* copy arguments cross page boundary.   */
549 #define GNTST_address_too_big (-11) /* transfer page address too large.      */
550 #define GNTST_eagain          (-12) /* Operation not done; try again.        */
551 
552 #define GNTTABOP_error_msgs {                   \
553     "okay",                                     \
554     "undefined error",                          \
555     "unrecognised domain id",                   \
556     "invalid grant reference",                  \
557     "invalid mapping handle",                   \
558     "invalid virtual address",                  \
559     "invalid device address",                   \
560     "no spare translation slot in the I/O MMU", \
561     "permission denied",                        \
562     "bad page",                                 \
563     "copy arguments cross page boundary",       \
564     "page address size too large",              \
565     "operation not done; try again"             \
566 }
567 
568 #endif /* __XEN_PUBLIC_GRANT_TABLE_H__ */
569