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