1 /* SPDX-License-Identifier: MIT */
2 /******************************************************************************
3  * grant_table.h
4  *
5  * Interface for granting foreign access to page frames, and receiving
6  * page-ownership transfers.
7  *
8  * Copyright (c) 2004, K A Fraser
9  */
10 
11 #ifndef __XEN_PUBLIC_GRANT_TABLE_H__
12 #define __XEN_PUBLIC_GRANT_TABLE_H__
13 
14 #include <xen/interface/xen.h>
15 
16 /***********************************
17  * GRANT TABLE REPRESENTATION
18  */
19 
20 /* Some rough guidelines on accessing and updating grant-table entries
21  * in a concurrency-safe manner. For more information, Linux contains a
22  * reference implementation for guest OSes (drivers/xen/grant_table.c, see
23  * http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=blob;f=drivers/xen/grant-table.c;hb=HEAD
24  *
25  * NB. WMB is a no-op on current-generation x86 processors. However, a
26  *     compiler barrier will still be required.
27  *
28  * Introducing a valid entry into the grant table:
29  *  1. Write ent->domid.
30  *  2. Write ent->frame:
31  *      GTF_permit_access:   Frame to which access is permitted.
32  *      GTF_accept_transfer: Pseudo-phys frame slot being filled by new
33  *                           frame, or zero if none.
34  *  3. Write memory barrier (WMB).
35  *  4. Write ent->flags, inc. valid type.
36  *
37  * Invalidating an unused GTF_permit_access entry:
38  *  1. flags = ent->flags.
39  *  2. Observe that !(flags & (GTF_reading|GTF_writing)).
40  *  3. Check result of SMP-safe CMPXCHG(&ent->flags, flags, 0).
41  *  NB. No need for WMB as reuse of entry is control-dependent on success of
42  *      step 3, and all architectures guarantee ordering of ctrl-dep writes.
43  *
44  * Invalidating an in-use GTF_permit_access entry:
45  *  This cannot be done directly. Request assistance from the domain controller
46  *  which can set a timeout on the use of a grant entry and take necessary
47  *  action. (NB. This is not yet implemented!).
48  *
49  * Invalidating an unused GTF_accept_transfer entry:
50  *  1. flags = ent->flags.
51  *  2. Observe that !(flags & GTF_transfer_committed). [*]
52  *  3. Check result of SMP-safe CMPXCHG(&ent->flags, flags, 0).
53  *  NB. No need for WMB as reuse of entry is control-dependent on success of
54  *      step 3, and all architectures guarantee ordering of ctrl-dep writes.
55  *  [*] If GTF_transfer_committed is set then the grant entry is 'committed'.
56  *      The guest must /not/ modify the grant entry until the address of the
57  *      transferred frame is written. It is safe for the guest to spin waiting
58  *      for this to occur (detect by observing GTF_transfer_completed in
59  *      ent->flags).
60  *
61  * Invalidating a committed GTF_accept_transfer entry:
62  *  1. Wait for (ent->flags & GTF_transfer_completed).
63  *
64  * Changing a GTF_permit_access from writable to read-only:
65  *  Use SMP-safe CMPXCHG to set GTF_readonly, while checking !GTF_writing.
66  *
67  * Changing a GTF_permit_access from read-only to writable:
68  *  Use SMP-safe bit-setting instruction.
69  */
70 
71 /*
72  * Reference to a grant entry in a specified domain's grant table.
73  */
74 typedef uint32_t grant_ref_t;
75 
76 /*
77  * A grant table comprises a packed array of grant entries in one or more
78  * page frames shared between Xen and a guest.
79  * [XEN]: This field is written by Xen and read by the sharing guest.
80  * [GST]: This field is written by the guest and read by Xen.
81  */
82 
83 /*
84  * Version 1 of the grant table entry structure is maintained largely for
85  * backwards compatibility.  New guests are recommended to support using
86  * version 2 to overcome version 1 limitations, but to default to version 1.
87  */
88 struct grant_entry_v1 {
89     /* GTF_xxx: various type and flag information.  [XEN,GST] */
90     uint16_t flags;
91     /* The domain being granted foreign privileges. [GST] */
92     domid_t  domid;
93     /*
94      * GTF_permit_access: GFN that @domid is allowed to map and access. [GST]
95      * GTF_accept_transfer: GFN that @domid is allowed to transfer into. [GST]
96      * GTF_transfer_completed: MFN whose ownership transferred by @domid
97      *                         (non-translated guests only). [XEN]
98      */
99     uint32_t frame;
100 };
101 
102 /* The first few grant table entries will be preserved across grant table
103  * version changes and may be pre-populated at domain creation by tools.
104  */
105 #define GNTTAB_NR_RESERVED_ENTRIES     8
106 #define GNTTAB_RESERVED_CONSOLE        0
107 #define GNTTAB_RESERVED_XENSTORE       1
108 
109 /*
110  * Type of grant entry.
111  *  GTF_invalid: This grant entry grants no privileges.
112  *  GTF_permit_access: Allow @domid to map/access @frame.
113  *  GTF_accept_transfer: Allow @domid to transfer ownership of one page frame
114  *                       to this guest. Xen writes the page number to @frame.
115  *  GTF_transitive: Allow @domid to transitively access a subrange of
116  *                  @trans_grant in @trans_domid.  No mappings are allowed.
117  */
118 #define GTF_invalid         (0U<<0)
119 #define GTF_permit_access   (1U<<0)
120 #define GTF_accept_transfer (2U<<0)
121 #define GTF_transitive      (3U<<0)
122 #define GTF_type_mask       (3U<<0)
123 
124 /*
125  * Subflags for GTF_permit_access and GTF_transitive.
126  *  GTF_readonly: Restrict @domid to read-only mappings and accesses. [GST]
127  *  GTF_reading: Grant entry is currently mapped for reading by @domid. [XEN]
128  *  GTF_writing: Grant entry is currently mapped for writing by @domid. [XEN]
129  * Further subflags for GTF_permit_access only.
130  *  GTF_PAT, GTF_PWT, GTF_PCD: (x86) cache attribute flags to be used for
131  *                             mappings of the grant [GST]
132  *  GTF_sub_page: Grant access to only a subrange of the page.  @domid
133  *                will only be allowed to copy from the grant, and not
134  *                map it. [GST]
135  */
136 #define _GTF_readonly       (2)
137 #define GTF_readonly        (1U<<_GTF_readonly)
138 #define _GTF_reading        (3)
139 #define GTF_reading         (1U<<_GTF_reading)
140 #define _GTF_writing        (4)
141 #define GTF_writing         (1U<<_GTF_writing)
142 #define _GTF_PWT            (5)
143 #define GTF_PWT             (1U<<_GTF_PWT)
144 #define _GTF_PCD            (6)
145 #define GTF_PCD             (1U<<_GTF_PCD)
146 #define _GTF_PAT            (7)
147 #define GTF_PAT             (1U<<_GTF_PAT)
148 #define _GTF_sub_page       (8)
149 #define GTF_sub_page        (1U<<_GTF_sub_page)
150 
151 /*
152  * Subflags for GTF_accept_transfer:
153  *  GTF_transfer_committed: Xen sets this flag to indicate that it is committed
154  *      to transferring ownership of a page frame. When a guest sees this flag
155  *      it must /not/ modify the grant entry until GTF_transfer_completed is
156  *      set by Xen.
157  *  GTF_transfer_completed: It is safe for the guest to spin-wait on this flag
158  *      after reading GTF_transfer_committed. Xen will always write the frame
159  *      address, followed by ORing this flag, in a timely manner.
160  */
161 #define _GTF_transfer_committed (2)
162 #define GTF_transfer_committed  (1U<<_GTF_transfer_committed)
163 #define _GTF_transfer_completed (3)
164 #define GTF_transfer_completed  (1U<<_GTF_transfer_completed)
165 
166 /*
167  * Version 2 grant table entries.  These fulfil the same role as
168  * version 1 entries, but can represent more complicated operations.
169  * Any given domain will have either a version 1 or a version 2 table,
170  * and every entry in the table will be the same version.
171  *
172  * The interface by which domains use grant references does not depend
173  * on the grant table version in use by the other domain.
174  */
175 
176 /*
177  * Version 1 and version 2 grant entries share a common prefix.  The
178  * fields of the prefix are documented as part of struct
179  * grant_entry_v1.
180  */
181 struct grant_entry_header {
182     uint16_t flags;
183     domid_t  domid;
184 };
185 
186 /*
187  * Version 2 of the grant entry structure.
188  */
189 union grant_entry_v2 {
190     struct grant_entry_header hdr;
191 
192     /*
193      * This member is used for V1-style full page grants, where either:
194      *
195      * -- hdr.type is GTF_accept_transfer, or
196      * -- hdr.type is GTF_permit_access and GTF_sub_page is not set.
197      *
198      * In that case, the frame field has the same semantics as the
199      * field of the same name in the V1 entry structure.
200      */
201     struct {
202         struct grant_entry_header hdr;
203         uint32_t pad0;
204         uint64_t frame;
205     } full_page;
206 
207     /*
208      * If the grant type is GTF_grant_access and GTF_sub_page is set,
209      * @domid is allowed to access bytes [@page_off,@page_off+@length)
210      * in frame @frame.
211      */
212     struct {
213         struct grant_entry_header hdr;
214         uint16_t page_off;
215         uint16_t length;
216         uint64_t frame;
217     } sub_page;
218 
219     /*
220      * If the grant is GTF_transitive, @domid is allowed to use the
221      * grant @gref in domain @trans_domid, as if it was the local
222      * domain.  Obviously, the transitive access must be compatible
223      * with the original grant.
224      *
225      * The current version of Xen does not allow transitive grants
226      * to be mapped.
227      */
228     struct {
229         struct grant_entry_header hdr;
230         domid_t trans_domid;
231         uint16_t pad0;
232         grant_ref_t gref;
233     } transitive;
234 
235     uint32_t __spacer[4]; /* Pad to a power of two */
236 };
237 
238 typedef uint16_t grant_status_t;
239 
240 /***********************************
241  * GRANT TABLE QUERIES AND USES
242  */
243 
244 #define GNTTABOP_map_grant_ref        0
245 #define GNTTABOP_unmap_grant_ref      1
246 #define GNTTABOP_setup_table          2
247 #define GNTTABOP_dump_table           3
248 #define GNTTABOP_transfer             4
249 #define GNTTABOP_copy                 5
250 #define GNTTABOP_query_size           6
251 #define GNTTABOP_unmap_and_replace    7
252 #define GNTTABOP_set_version          8
253 #define GNTTABOP_get_status_frames    9
254 #define GNTTABOP_get_version          10
255 #define GNTTABOP_swap_grant_ref	      11
256 #define GNTTABOP_cache_flush	      12
257 /* ` } */
258 
259 /*
260  * Handle to track a mapping created via a grant reference.
261  */
262 typedef uint32_t grant_handle_t;
263 
264 /*
265  * GNTTABOP_map_grant_ref: Map the grant entry (<dom>,<ref>) for access
266  * by devices and/or host CPUs. If successful, <handle> is a tracking number
267  * that must be presented later to destroy the mapping(s). On error, <status>
268  * is a negative status code.
269  * NOTES:
270  *  1. If GNTMAP_device_map is specified then <dev_bus_addr> is the address
271  *     via which I/O devices may access the granted frame.
272  *  2. If GNTMAP_host_map is specified then a mapping will be added at
273  *     either a host virtual address in the current address space, or at
274  *     a PTE at the specified machine address.  The type of mapping to
275  *     perform is selected through the GNTMAP_contains_pte flag, and the
276  *     address is specified in <host_addr>.
277  *  3. Mappings should only be destroyed via GNTTABOP_unmap_grant_ref. If a
278  *     host mapping is destroyed by other means then it is *NOT* guaranteed
279  *     to be accounted to the correct grant reference!
280  */
281 struct gnttab_map_grant_ref {
282     /* IN parameters. */
283     uint64_t host_addr;
284     uint32_t flags;               /* GNTMAP_* */
285     grant_ref_t ref;
286     domid_t  dom;
287     /* OUT parameters. */
288     int16_t  status;              /* GNTST_* */
289     grant_handle_t handle;
290     uint64_t dev_bus_addr;
291 };
292 DEFINE_GUEST_HANDLE_STRUCT(gnttab_map_grant_ref);
293 
294 /*
295  * GNTTABOP_unmap_grant_ref: Destroy one or more grant-reference mappings
296  * tracked by <handle>. If <host_addr> or <dev_bus_addr> is zero, that
297  * field is ignored. If non-zero, they must refer to a device/host mapping
298  * that is tracked by <handle>
299  * NOTES:
300  *  1. The call may fail in an undefined manner if either mapping is not
301  *     tracked by <handle>.
302  *  3. After executing a batch of unmaps, it is guaranteed that no stale
303  *     mappings will remain in the device or host TLBs.
304  */
305 struct gnttab_unmap_grant_ref {
306     /* IN parameters. */
307     uint64_t host_addr;
308     uint64_t dev_bus_addr;
309     grant_handle_t handle;
310     /* OUT parameters. */
311     int16_t  status;              /* GNTST_* */
312 };
313 DEFINE_GUEST_HANDLE_STRUCT(gnttab_unmap_grant_ref);
314 
315 /*
316  * GNTTABOP_setup_table: Set up a grant table for <dom> comprising at least
317  * <nr_frames> pages. The frame addresses are written to the <frame_list>.
318  * Only <nr_frames> addresses are written, even if the table is larger.
319  * NOTES:
320  *  1. <dom> may be specified as DOMID_SELF.
321  *  2. Only a sufficiently-privileged domain may specify <dom> != DOMID_SELF.
322  *  3. Xen may not support more than a single grant-table page per domain.
323  */
324 struct gnttab_setup_table {
325     /* IN parameters. */
326     domid_t  dom;
327     uint32_t nr_frames;
328     /* OUT parameters. */
329     int16_t  status;              /* GNTST_* */
330     GUEST_HANDLE(xen_pfn_t) frame_list;
331 };
332 DEFINE_GUEST_HANDLE_STRUCT(gnttab_setup_table);
333 
334 /*
335  * GNTTABOP_dump_table: Dump the contents of the grant table to the
336  * xen console. Debugging use only.
337  */
338 struct gnttab_dump_table {
339     /* IN parameters. */
340     domid_t dom;
341     /* OUT parameters. */
342     int16_t status;               /* GNTST_* */
343 };
344 DEFINE_GUEST_HANDLE_STRUCT(gnttab_dump_table);
345 
346 /*
347  * GNTTABOP_transfer: Transfer <frame> to a foreign domain. The foreign domain
348  * has previously registered its interest in the transfer via <domid, ref>.
349  *
350  * Note that, even if the transfer fails, the specified page no longer belongs
351  * to the calling domain *unless* the error is GNTST_bad_page.
352  *
353  * Note further that only PV guests can use this operation.
354  */
355 struct gnttab_transfer {
356     /* IN parameters. */
357     xen_pfn_t     mfn;
358     domid_t       domid;
359     grant_ref_t   ref;
360     /* OUT parameters. */
361     int16_t       status;
362 };
363 DEFINE_GUEST_HANDLE_STRUCT(gnttab_transfer);
364 
365 /*
366  * GNTTABOP_copy: Hypervisor based copy
367  * source and destinations can be eithers MFNs or, for foreign domains,
368  * grant references. the foreign domain has to grant read/write access
369  * in its grant table.
370  *
371  * The flags specify what type source and destinations are (either MFN
372  * or grant reference).
373  *
374  * Note that this can also be used to copy data between two domains
375  * via a third party if the source and destination domains had previously
376  * grant appropriate access to their pages to the third party.
377  *
378  * source_offset specifies an offset in the source frame, dest_offset
379  * the offset in the target frame and  len specifies the number of
380  * bytes to be copied.
381  */
382 
383 #define _GNTCOPY_source_gref      (0)
384 #define GNTCOPY_source_gref       (1<<_GNTCOPY_source_gref)
385 #define _GNTCOPY_dest_gref        (1)
386 #define GNTCOPY_dest_gref         (1<<_GNTCOPY_dest_gref)
387 
388 struct gnttab_copy {
389     /* IN parameters. */
390     struct gnttab_copy_ptr {
391         union {
392             grant_ref_t ref;
393             xen_pfn_t   gmfn;
394         } u;
395         domid_t  domid;
396         uint16_t offset;
397     } source, dest;
398     uint16_t      len;
399     uint16_t      flags;          /* GNTCOPY_* */
400     /* OUT parameters. */
401     int16_t       status;
402 };
403 DEFINE_GUEST_HANDLE_STRUCT(gnttab_copy);
404 
405 /*
406  * GNTTABOP_query_size: Query the current and maximum sizes of the shared
407  * grant table.
408  * NOTES:
409  *  1. <dom> may be specified as DOMID_SELF.
410  *  2. Only a sufficiently-privileged domain may specify <dom> != DOMID_SELF.
411  */
412 struct gnttab_query_size {
413     /* IN parameters. */
414     domid_t  dom;
415     /* OUT parameters. */
416     uint32_t nr_frames;
417     uint32_t max_nr_frames;
418     int16_t  status;              /* GNTST_* */
419 };
420 DEFINE_GUEST_HANDLE_STRUCT(gnttab_query_size);
421 
422 /*
423  * GNTTABOP_unmap_and_replace: Destroy one or more grant-reference mappings
424  * tracked by <handle> but atomically replace the page table entry with one
425  * pointing to the machine address under <new_addr>.  <new_addr> will be
426  * redirected to the null entry.
427  * NOTES:
428  *  1. The call may fail in an undefined manner if either mapping is not
429  *     tracked by <handle>.
430  *  2. After executing a batch of unmaps, it is guaranteed that no stale
431  *     mappings will remain in the device or host TLBs.
432  */
433 struct gnttab_unmap_and_replace {
434     /* IN parameters. */
435     uint64_t host_addr;
436     uint64_t new_addr;
437     grant_handle_t handle;
438     /* OUT parameters. */
439     int16_t  status;              /* GNTST_* */
440 };
441 DEFINE_GUEST_HANDLE_STRUCT(gnttab_unmap_and_replace);
442 
443 /*
444  * GNTTABOP_set_version: Request a particular version of the grant
445  * table shared table structure.  This operation may be used to toggle
446  * between different versions, but must be performed while no grants
447  * are active.  The only defined versions are 1 and 2.
448  */
449 struct gnttab_set_version {
450     /* IN/OUT parameters */
451     uint32_t version;
452 };
453 DEFINE_GUEST_HANDLE_STRUCT(gnttab_set_version);
454 
455 /*
456  * GNTTABOP_get_status_frames: Get the list of frames used to store grant
457  * status for <dom>. In grant format version 2, the status is separated
458  * from the other shared grant fields to allow more efficient synchronization
459  * using barriers instead of atomic cmpexch operations.
460  * <nr_frames> specify the size of vector <frame_list>.
461  * The frame addresses are returned in the <frame_list>.
462  * Only <nr_frames> addresses are returned, even if the table is larger.
463  * NOTES:
464  *  1. <dom> may be specified as DOMID_SELF.
465  *  2. Only a sufficiently-privileged domain may specify <dom> != DOMID_SELF.
466  */
467 struct gnttab_get_status_frames {
468     /* IN parameters. */
469     uint32_t nr_frames;
470     domid_t  dom;
471     /* OUT parameters. */
472     int16_t  status;              /* GNTST_* */
473     GUEST_HANDLE(uint64_t) frame_list;
474 };
475 DEFINE_GUEST_HANDLE_STRUCT(gnttab_get_status_frames);
476 
477 /*
478  * GNTTABOP_get_version: Get the grant table version which is in
479  * effect for domain <dom>.
480  */
481 struct gnttab_get_version {
482     /* IN parameters */
483     domid_t dom;
484     uint16_t pad;
485     /* OUT parameters */
486     uint32_t version;
487 };
488 DEFINE_GUEST_HANDLE_STRUCT(gnttab_get_version);
489 
490 /*
491  * GNTTABOP_swap_grant_ref: Swap the contents of two grant entries.
492  */
493 struct gnttab_swap_grant_ref {
494     /* IN parameters */
495     grant_ref_t ref_a;
496     grant_ref_t ref_b;
497     /* OUT parameters */
498     int16_t status;             /* GNTST_* */
499 };
500 DEFINE_GUEST_HANDLE_STRUCT(gnttab_swap_grant_ref);
501 
502 /*
503  * Issue one or more cache maintenance operations on a portion of a
504  * page granted to the calling domain by a foreign domain.
505  */
506 struct gnttab_cache_flush {
507     union {
508         uint64_t dev_bus_addr;
509         grant_ref_t ref;
510     } a;
511     uint16_t offset; /* offset from start of grant */
512     uint16_t length; /* size within the grant */
513 #define GNTTAB_CACHE_CLEAN          (1u<<0)
514 #define GNTTAB_CACHE_INVAL          (1u<<1)
515 #define GNTTAB_CACHE_SOURCE_GREF    (1u<<31)
516     uint32_t op;
517 };
518 DEFINE_GUEST_HANDLE_STRUCT(gnttab_cache_flush);
519 
520 /*
521  * Bitfield values for gnttab_map_grant_ref.flags.
522  */
523  /* Map the grant entry for access by I/O devices. */
524 #define _GNTMAP_device_map      (0)
525 #define GNTMAP_device_map       (1<<_GNTMAP_device_map)
526  /* Map the grant entry for access by host CPUs. */
527 #define _GNTMAP_host_map        (1)
528 #define GNTMAP_host_map         (1<<_GNTMAP_host_map)
529  /* Accesses to the granted frame will be restricted to read-only access. */
530 #define _GNTMAP_readonly        (2)
531 #define GNTMAP_readonly         (1<<_GNTMAP_readonly)
532  /*
533   * GNTMAP_host_map subflag:
534   *  0 => The host mapping is usable only by the guest OS.
535   *  1 => The host mapping is usable by guest OS + current application.
536   */
537 #define _GNTMAP_application_map (3)
538 #define GNTMAP_application_map  (1<<_GNTMAP_application_map)
539 
540  /*
541   * GNTMAP_contains_pte subflag:
542   *  0 => This map request contains a host virtual address.
543   *  1 => This map request contains the machine addess of the PTE to update.
544   */
545 #define _GNTMAP_contains_pte    (4)
546 #define GNTMAP_contains_pte     (1<<_GNTMAP_contains_pte)
547 
548 /*
549  * Bits to be placed in guest kernel available PTE bits (architecture
550  * dependent; only supported when XENFEAT_gnttab_map_avail_bits is set).
551  */
552 #define _GNTMAP_guest_avail0    (16)
553 #define GNTMAP_guest_avail_mask ((uint32_t)~0 << _GNTMAP_guest_avail0)
554 
555 /*
556  * Values for error status returns. All errors are -ve.
557  */
558 #define GNTST_okay             (0)  /* Normal return.                        */
559 #define GNTST_general_error    (-1) /* General undefined error.              */
560 #define GNTST_bad_domain       (-2) /* Unrecognsed domain id.                */
561 #define GNTST_bad_gntref       (-3) /* Unrecognised or inappropriate gntref. */
562 #define GNTST_bad_handle       (-4) /* Unrecognised or inappropriate handle. */
563 #define GNTST_bad_virt_addr    (-5) /* Inappropriate virtual address to map. */
564 #define GNTST_bad_dev_addr     (-6) /* Inappropriate device address to unmap.*/
565 #define GNTST_no_device_space  (-7) /* Out of space in I/O MMU.              */
566 #define GNTST_permission_denied (-8) /* Not enough privilege for operation.  */
567 #define GNTST_bad_page         (-9) /* Specified page was invalid for op.    */
568 #define GNTST_bad_copy_arg    (-10) /* copy arguments cross page boundary.   */
569 #define GNTST_address_too_big (-11) /* transfer page address too large.      */
570 #define GNTST_eagain          (-12) /* Operation not done; try again.        */
571 #define GNTST_no_space        (-13) /* Out of space (handles etc).           */
572 
573 #define GNTTABOP_error_msgs {                   \
574     "okay",                                     \
575     "undefined error",                          \
576     "unrecognised domain id",                   \
577     "invalid grant reference",                  \
578     "invalid mapping handle",                   \
579     "invalid virtual address",                  \
580     "invalid device address",                   \
581     "no spare translation slot in the I/O MMU", \
582     "permission denied",                        \
583     "bad page",                                 \
584     "copy arguments cross page boundary",       \
585     "page address size too large",              \
586     "operation not done; try again",            \
587     "out of space",                             \
588 }
589 
590 #endif /* __XEN_PUBLIC_GRANT_TABLE_H__ */
591