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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 */
74typedef 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 */
88struct 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 */
181struct grant_entry_header {
182 uint16_t flags;
183 domid_t domid;
184};
185
186/*
187 * Version 2 of the grant entry structure.
188 */
189union 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
238typedef 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 */
262typedef 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 */
281struct 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};
292DEFINE_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 */
305struct 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};
313DEFINE_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 */
324struct 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};
332DEFINE_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 */
338struct gnttab_dump_table {
339 /* IN parameters. */
340 domid_t dom;
341 /* OUT parameters. */
342 int16_t status; /* GNTST_* */
343};
344DEFINE_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 */
355struct 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};
363DEFINE_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
388struct 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};
403DEFINE_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 */
412struct 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};
420DEFINE_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 */
433struct 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};
441DEFINE_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 */
449struct gnttab_set_version {
450 /* IN/OUT parameters */
451 uint32_t version;
452};
453DEFINE_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 */
467struct 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};
475DEFINE_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 */
481struct gnttab_get_version {
482 /* IN parameters */
483 domid_t dom;
484 uint16_t pad;
485 /* OUT parameters */
486 uint32_t version;
487};
488DEFINE_GUEST_HANDLE_STRUCT(gnttab_get_version);
489
490/*
491 * GNTTABOP_swap_grant_ref: Swap the contents of two grant entries.
492 */
493struct 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};
500DEFINE_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 */
506struct 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};
518DEFINE_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__ */