1 /******************************************************************************
4 * Interface for granting foreign access to page frames, and receiving
5 * page-ownership transfers.
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:
14 * The above copyright notice and this permission notice shall be included in
15 * all copies or substantial portions of the Software.
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.
25 * Copyright (c) 2004, K A Fraser
28 #ifndef __XEN_PUBLIC_GRANT_TABLE_H__
29 #define __XEN_PUBLIC_GRANT_TABLE_H__
34 * `incontents 150 gnttab Grant Tables
36 * Xen's grant tables provide a generic mechanism to memory sharing
37 * between domains. This shared memory interface underpins the split
38 * device drivers for block and network IO.
40 * Each domain has its own grant table. This is a data structure that
41 * is shared with Xen; it allows the domain to tell Xen what kind of
42 * permissions other domains have on its pages. Entries in the grant
43 * table are identified by grant references. A grant reference is an
44 * integer, which indexes into the grant table. It acts as a
45 * capability which the grantee can use to perform operations on the
48 * This capability-based system allows shared-memory communications
49 * between unprivileged domains. A grant reference also encapsulates
50 * the details of a shared page, removing the need for a domain to
51 * know the real machine address of a page it is sharing. This makes
52 * it possible to share memory correctly with domains running in
53 * fully virtualised memory.
56 /***********************************
57 * GRANT TABLE REPRESENTATION
60 /* Some rough guidelines on accessing and updating grant-table entries
61 * in a concurrency-safe manner. For more information, Linux contains a
62 * reference implementation for guest OSes (drivers/xen/grant_table.c, see
63 * http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=blob;f=drivers/xen/grant-table.c;hb=HEAD
65 * NB. WMB is a no-op on current-generation x86 processors. However, a
66 * compiler barrier will still be required.
68 * Introducing a valid entry into the grant table:
69 * 1. Write ent->domid.
70 * 2. Write ent->frame:
71 * GTF_permit_access: Frame to which access is permitted.
72 * GTF_accept_transfer: Pseudo-phys frame slot being filled by new
73 * frame, or zero if none.
74 * 3. Write memory barrier (WMB).
75 * 4. Write ent->flags, inc. valid type.
77 * Invalidating an unused GTF_permit_access entry:
78 * 1. flags = ent->flags.
79 * 2. Observe that !(flags & (GTF_reading|GTF_writing)).
80 * 3. Check result of SMP-safe CMPXCHG(&ent->flags, flags, 0).
81 * NB. No need for WMB as reuse of entry is control-dependent on success of
82 * step 3, and all architectures guarantee ordering of ctrl-dep writes.
84 * Invalidating an in-use GTF_permit_access entry:
85 * This cannot be done directly. Request assistance from the domain controller
86 * which can set a timeout on the use of a grant entry and take necessary
87 * action. (NB. This is not yet implemented!).
89 * Invalidating an unused GTF_accept_transfer entry:
90 * 1. flags = ent->flags.
91 * 2. Observe that !(flags & GTF_transfer_committed). [*]
92 * 3. Check result of SMP-safe CMPXCHG(&ent->flags, flags, 0).
93 * NB. No need for WMB as reuse of entry is control-dependent on success of
94 * step 3, and all architectures guarantee ordering of ctrl-dep writes.
95 * [*] If GTF_transfer_committed is set then the grant entry is 'committed'.
96 * The guest must /not/ modify the grant entry until the address of the
97 * transferred frame is written. It is safe for the guest to spin waiting
98 * for this to occur (detect by observing GTF_transfer_completed in
101 * Invalidating a committed GTF_accept_transfer entry:
102 * 1. Wait for (ent->flags & GTF_transfer_completed).
104 * Changing a GTF_permit_access from writable to read-only:
105 * Use SMP-safe CMPXCHG to set GTF_readonly, while checking !GTF_writing.
107 * Changing a GTF_permit_access from read-only to writable:
108 * Use SMP-safe bit-setting instruction.
112 * Reference to a grant entry in a specified domain's grant table.
114 typedef uint32_t grant_ref_t;
117 * A grant table comprises a packed array of grant entries in one or more
118 * page frames shared between Xen and a guest.
119 * [XEN]: This field is written by Xen and read by the sharing guest.
120 * [GST]: This field is written by the guest and read by Xen.
124 * Version 1 of the grant table entry structure is maintained purely
125 * for backwards compatibility. New guests should use version 2.
127 #if __XEN_INTERFACE_VERSION__ < 0x0003020a
128 #define grant_entry_v1 grant_entry
129 #define grant_entry_v1_t grant_entry_t
131 struct grant_entry_v1 {
132 /* GTF_xxx: various type and flag information. [XEN,GST] */
134 /* The domain being granted foreign privileges. [GST] */
137 * GTF_permit_access: Frame that @domid is allowed to map and access. [GST]
138 * GTF_accept_transfer: Frame whose ownership transferred by @domid. [XEN]
142 typedef struct grant_entry_v1 grant_entry_v1_t;
144 /* The first few grant table entries will be preserved across grant table
145 * version changes and may be pre-populated at domain creation by tools.
147 #define GNTTAB_NR_RESERVED_ENTRIES 8
148 #define GNTTAB_RESERVED_CONSOLE 0
149 #define GNTTAB_RESERVED_XENSTORE 1
152 * Type of grant entry.
153 * GTF_invalid: This grant entry grants no privileges.
154 * GTF_permit_access: Allow @domid to map/access @frame.
155 * GTF_accept_transfer: Allow @domid to transfer ownership of one page frame
156 * to this guest. Xen writes the page number to @frame.
157 * GTF_transitive: Allow @domid to transitively access a subrange of
158 * @trans_grant in @trans_domid. No mappings are allowed.
160 #define GTF_invalid (0U<<0)
161 #define GTF_permit_access (1U<<0)
162 #define GTF_accept_transfer (2U<<0)
163 #define GTF_transitive (3U<<0)
164 #define GTF_type_mask (3U<<0)
167 * Subflags for GTF_permit_access.
168 * GTF_readonly: Restrict @domid to read-only mappings and accesses. [GST]
169 * GTF_reading: Grant entry is currently mapped for reading by @domid. [XEN]
170 * GTF_writing: Grant entry is currently mapped for writing by @domid. [XEN]
171 * GTF_PAT, GTF_PWT, GTF_PCD: (x86) cache attribute flags for the grant [GST]
172 * GTF_sub_page: Grant access to only a subrange of the page. @domid
173 * will only be allowed to copy from the grant, and not
176 #define _GTF_readonly (2)
177 #define GTF_readonly (1U<<_GTF_readonly)
178 #define _GTF_reading (3)
179 #define GTF_reading (1U<<_GTF_reading)
180 #define _GTF_writing (4)
181 #define GTF_writing (1U<<_GTF_writing)
183 #define GTF_PWT (1U<<_GTF_PWT)
185 #define GTF_PCD (1U<<_GTF_PCD)
187 #define GTF_PAT (1U<<_GTF_PAT)
188 #define _GTF_sub_page (8)
189 #define GTF_sub_page (1U<<_GTF_sub_page)
192 * Subflags for GTF_accept_transfer:
193 * GTF_transfer_committed: Xen sets this flag to indicate that it is committed
194 * to transferring ownership of a page frame. When a guest sees this flag
195 * it must /not/ modify the grant entry until GTF_transfer_completed is
197 * GTF_transfer_completed: It is safe for the guest to spin-wait on this flag
198 * after reading GTF_transfer_committed. Xen will always write the frame
199 * address, followed by ORing this flag, in a timely manner.
201 #define _GTF_transfer_committed (2)
202 #define GTF_transfer_committed (1U<<_GTF_transfer_committed)
203 #define _GTF_transfer_completed (3)
204 #define GTF_transfer_completed (1U<<_GTF_transfer_completed)
207 * Version 2 grant table entries. These fulfil the same role as
208 * version 1 entries, but can represent more complicated operations.
209 * Any given domain will have either a version 1 or a version 2 table,
210 * and every entry in the table will be the same version.
212 * The interface by which domains use grant references does not depend
213 * on the grant table version in use by the other domain.
215 #if __XEN_INTERFACE_VERSION__ >= 0x0003020a
217 * Version 1 and version 2 grant entries share a common prefix. The
218 * fields of the prefix are documented as part of struct
221 struct grant_entry_header {
225 typedef struct grant_entry_header grant_entry_header_t;
228 * Version 2 of the grant entry structure.
230 union grant_entry_v2 {
231 grant_entry_header_t hdr;
234 * This member is used for V1-style full page grants, where either:
236 * -- hdr.type is GTF_accept_transfer, or
237 * -- hdr.type is GTF_permit_access and GTF_sub_page is not set.
239 * In that case, the frame field has the same semantics as the
240 * field of the same name in the V1 entry structure.
243 grant_entry_header_t hdr;
249 * If the grant type is GTF_grant_access and GTF_sub_page is set,
250 * @domid is allowed to access bytes [@page_off,@page_off+@length)
254 grant_entry_header_t hdr;
261 * If the grant is GTF_transitive, @domid is allowed to use the
262 * grant @gref in domain @trans_domid, as if it was the local
263 * domain. Obviously, the transitive access must be compatible
264 * with the original grant.
266 * The current version of Xen does not allow transitive grants
270 grant_entry_header_t hdr;
276 uint32_t __spacer[4]; /* Pad to a power of two */
278 typedef union grant_entry_v2 grant_entry_v2_t;
280 typedef uint16_t grant_status_t;
282 #endif /* __XEN_INTERFACE_VERSION__ */
284 /***********************************
285 * GRANT TABLE QUERIES AND USES
288 /* ` enum neg_errnoval
289 * ` HYPERVISOR_grant_table_op(enum grant_table_op cmd,
291 * ` unsigned int count)
294 * @args points to an array of a per-command data structure. The array
298 /* ` enum grant_table_op { // GNTTABOP_* => struct gnttab_* */
299 #define GNTTABOP_map_grant_ref 0
300 #define GNTTABOP_unmap_grant_ref 1
301 #define GNTTABOP_setup_table 2
302 #define GNTTABOP_dump_table 3
303 #define GNTTABOP_transfer 4
304 #define GNTTABOP_copy 5
305 #define GNTTABOP_query_size 6
306 #define GNTTABOP_unmap_and_replace 7
307 #if __XEN_INTERFACE_VERSION__ >= 0x0003020a
308 #define GNTTABOP_set_version 8
309 #define GNTTABOP_get_status_frames 9
310 #define GNTTABOP_get_version 10
311 #define GNTTABOP_swap_grant_ref 11
312 #endif /* __XEN_INTERFACE_VERSION__ */
316 * Handle to track a mapping created via a grant reference.
318 typedef uint32_t grant_handle_t;
321 * GNTTABOP_map_grant_ref: Map the grant entry (<dom>,<ref>) for access
322 * by devices and/or host CPUs. If successful, <handle> is a tracking number
323 * that must be presented later to destroy the mapping(s). On error, <handle>
324 * is a negative status code.
326 * 1. If GNTMAP_device_map is specified then <dev_bus_addr> is the address
327 * via which I/O devices may access the granted frame.
328 * 2. If GNTMAP_host_map is specified then a mapping will be added at
329 * either a host virtual address in the current address space, or at
330 * a PTE at the specified machine address. The type of mapping to
331 * perform is selected through the GNTMAP_contains_pte flag, and the
332 * address is specified in <host_addr>.
333 * 3. Mappings should only be destroyed via GNTTABOP_unmap_grant_ref. If a
334 * host mapping is destroyed by other means then it is *NOT* guaranteed
335 * to be accounted to the correct grant reference!
337 struct gnttab_map_grant_ref {
340 uint32_t flags; /* GNTMAP_* */
343 /* OUT parameters. */
344 int16_t status; /* => enum grant_status */
345 grant_handle_t handle;
346 uint64_t dev_bus_addr;
348 typedef struct gnttab_map_grant_ref gnttab_map_grant_ref_t;
349 DEFINE_XEN_GUEST_HANDLE(gnttab_map_grant_ref_t);
352 * GNTTABOP_unmap_grant_ref: Destroy one or more grant-reference mappings
353 * tracked by <handle>. If <host_addr> or <dev_bus_addr> is zero, that
354 * field is ignored. If non-zero, they must refer to a device/host mapping
355 * that is tracked by <handle>
357 * 1. The call may fail in an undefined manner if either mapping is not
358 * tracked by <handle>.
359 * 3. After executing a batch of unmaps, it is guaranteed that no stale
360 * mappings will remain in the device or host TLBs.
362 struct gnttab_unmap_grant_ref {
365 uint64_t dev_bus_addr;
366 grant_handle_t handle;
367 /* OUT parameters. */
368 int16_t status; /* => enum grant_status */
370 typedef struct gnttab_unmap_grant_ref gnttab_unmap_grant_ref_t;
371 DEFINE_XEN_GUEST_HANDLE(gnttab_unmap_grant_ref_t);
374 * GNTTABOP_setup_table: Set up a grant table for <dom> comprising at least
375 * <nr_frames> pages. The frame addresses are written to the <frame_list>.
376 * Only <nr_frames> addresses are written, even if the table is larger.
378 * 1. <dom> may be specified as DOMID_SELF.
379 * 2. Only a sufficiently-privileged domain may specify <dom> != DOMID_SELF.
380 * 3. Xen may not support more than a single grant-table page per domain.
382 struct gnttab_setup_table {
386 /* OUT parameters. */
387 int16_t status; /* => enum grant_status */
388 XEN_GUEST_HANDLE(ulong) frame_list;
390 typedef struct gnttab_setup_table gnttab_setup_table_t;
391 DEFINE_XEN_GUEST_HANDLE(gnttab_setup_table_t);
394 * GNTTABOP_dump_table: Dump the contents of the grant table to the
395 * xen console. Debugging use only.
397 struct gnttab_dump_table {
400 /* OUT parameters. */
401 int16_t status; /* => enum grant_status */
403 typedef struct gnttab_dump_table gnttab_dump_table_t;
404 DEFINE_XEN_GUEST_HANDLE(gnttab_dump_table_t);
407 * GNTTABOP_transfer_grant_ref: Transfer <frame> to a foreign domain. The
408 * foreign domain has previously registered its interest in the transfer via
411 * Note that, even if the transfer fails, the specified page no longer belongs
412 * to the calling domain *unless* the error is GNTST_bad_page.
414 struct gnttab_transfer {
419 /* OUT parameters. */
422 typedef struct gnttab_transfer gnttab_transfer_t;
423 DEFINE_XEN_GUEST_HANDLE(gnttab_transfer_t);
427 * GNTTABOP_copy: Hypervisor based copy
428 * source and destinations can be eithers MFNs or, for foreign domains,
429 * grant references. the foreign domain has to grant read/write access
430 * in its grant table.
432 * The flags specify what type source and destinations are (either MFN
433 * or grant reference).
435 * Note that this can also be used to copy data between two domains
436 * via a third party if the source and destination domains had previously
437 * grant appropriate access to their pages to the third party.
439 * source_offset specifies an offset in the source frame, dest_offset
440 * the offset in the target frame and len specifies the number of
441 * bytes to be copied.
444 #define _GNTCOPY_source_gref (0)
445 #define GNTCOPY_source_gref (1<<_GNTCOPY_source_gref)
446 #define _GNTCOPY_dest_gref (1)
447 #define GNTCOPY_dest_gref (1<<_GNTCOPY_dest_gref)
448 #define _GNTCOPY_can_fail (2)
449 #define GNTCOPY_can_fail (1<<_GNTCOPY_can_fail)
462 uint16_t flags; /* GNTCOPY_* */
463 /* OUT parameters. */
466 typedef struct gnttab_copy gnttab_copy_t;
467 DEFINE_XEN_GUEST_HANDLE(gnttab_copy_t);
470 * GNTTABOP_query_size: Query the current and maximum sizes of the shared
473 * 1. <dom> may be specified as DOMID_SELF.
474 * 2. Only a sufficiently-privileged domain may specify <dom> != DOMID_SELF.
476 struct gnttab_query_size {
479 /* OUT parameters. */
481 uint32_t max_nr_frames;
482 int16_t status; /* => enum grant_status */
484 typedef struct gnttab_query_size gnttab_query_size_t;
485 DEFINE_XEN_GUEST_HANDLE(gnttab_query_size_t);
488 * GNTTABOP_unmap_and_replace: Destroy one or more grant-reference mappings
489 * tracked by <handle> but atomically replace the page table entry with one
490 * pointing to the machine address under <new_addr>. <new_addr> will be
491 * redirected to the null entry.
493 * 1. The call may fail in an undefined manner if either mapping is not
494 * tracked by <handle>.
495 * 2. After executing a batch of unmaps, it is guaranteed that no stale
496 * mappings will remain in the device or host TLBs.
498 struct gnttab_unmap_and_replace {
502 grant_handle_t handle;
503 /* OUT parameters. */
504 int16_t status; /* => enum grant_status */
506 typedef struct gnttab_unmap_and_replace gnttab_unmap_and_replace_t;
507 DEFINE_XEN_GUEST_HANDLE(gnttab_unmap_and_replace_t);
509 #if __XEN_INTERFACE_VERSION__ >= 0x0003020a
511 * GNTTABOP_set_version: Request a particular version of the grant
512 * table shared table structure. This operation can only be performed
513 * once in any given domain. It must be performed before any grants
514 * are activated; otherwise, the domain will be stuck with version 1.
515 * The only defined versions are 1 and 2.
517 struct gnttab_set_version {
518 /* IN/OUT parameters */
521 typedef struct gnttab_set_version gnttab_set_version_t;
522 DEFINE_XEN_GUEST_HANDLE(gnttab_set_version_t);
526 * GNTTABOP_get_status_frames: Get the list of frames used to store grant
527 * status for <dom>. In grant format version 2, the status is separated
528 * from the other shared grant fields to allow more efficient synchronization
529 * using barriers instead of atomic cmpexch operations.
530 * <nr_frames> specify the size of vector <frame_list>.
531 * The frame addresses are returned in the <frame_list>.
532 * Only <nr_frames> addresses are returned, even if the table is larger.
534 * 1. <dom> may be specified as DOMID_SELF.
535 * 2. Only a sufficiently-privileged domain may specify <dom> != DOMID_SELF.
537 struct gnttab_get_status_frames {
541 /* OUT parameters. */
542 int16_t status; /* => enum grant_status */
543 XEN_GUEST_HANDLE(uint64_t) frame_list;
545 typedef struct gnttab_get_status_frames gnttab_get_status_frames_t;
546 DEFINE_XEN_GUEST_HANDLE(gnttab_get_status_frames_t);
549 * GNTTABOP_get_version: Get the grant table version which is in
550 * effect for domain <dom>.
552 struct gnttab_get_version {
559 typedef struct gnttab_get_version gnttab_get_version_t;
560 DEFINE_XEN_GUEST_HANDLE(gnttab_get_version_t);
563 * GNTTABOP_swap_grant_ref: Swap the contents of two grant entries.
565 struct gnttab_swap_grant_ref {
570 int16_t status; /* => enum grant_status */
572 typedef struct gnttab_swap_grant_ref gnttab_swap_grant_ref_t;
573 DEFINE_XEN_GUEST_HANDLE(gnttab_swap_grant_ref_t);
575 #endif /* __XEN_INTERFACE_VERSION__ */
578 * Bitfield values for gnttab_map_grant_ref.flags.
580 /* Map the grant entry for access by I/O devices. */
581 #define _GNTMAP_device_map (0)
582 #define GNTMAP_device_map (1<<_GNTMAP_device_map)
583 /* Map the grant entry for access by host CPUs. */
584 #define _GNTMAP_host_map (1)
585 #define GNTMAP_host_map (1<<_GNTMAP_host_map)
586 /* Accesses to the granted frame will be restricted to read-only access. */
587 #define _GNTMAP_readonly (2)
588 #define GNTMAP_readonly (1<<_GNTMAP_readonly)
590 * GNTMAP_host_map subflag:
591 * 0 => The host mapping is usable only by the guest OS.
592 * 1 => The host mapping is usable by guest OS + current application.
594 #define _GNTMAP_application_map (3)
595 #define GNTMAP_application_map (1<<_GNTMAP_application_map)
598 * GNTMAP_contains_pte subflag:
599 * 0 => This map request contains a host virtual address.
600 * 1 => This map request contains the machine addess of the PTE to update.
602 #define _GNTMAP_contains_pte (4)
603 #define GNTMAP_contains_pte (1<<_GNTMAP_contains_pte)
605 #define _GNTMAP_can_fail (5)
606 #define GNTMAP_can_fail (1<<_GNTMAP_can_fail)
609 * Bits to be placed in guest kernel available PTE bits (architecture
610 * dependent; only supported when XENFEAT_gnttab_map_avail_bits is set).
612 #define _GNTMAP_guest_avail0 (16)
613 #define GNTMAP_guest_avail_mask ((uint32_t)~0 << _GNTMAP_guest_avail0)
616 * Values for error status returns. All errors are -ve.
618 /* ` enum grant_status { */
619 #define GNTST_okay (0) /* Normal return. */
620 #define GNTST_general_error (-1) /* General undefined error. */
621 #define GNTST_bad_domain (-2) /* Unrecognsed domain id. */
622 #define GNTST_bad_gntref (-3) /* Unrecognised or inappropriate gntref. */
623 #define GNTST_bad_handle (-4) /* Unrecognised or inappropriate handle. */
624 #define GNTST_bad_virt_addr (-5) /* Inappropriate virtual address to map. */
625 #define GNTST_bad_dev_addr (-6) /* Inappropriate device address to unmap.*/
626 #define GNTST_no_device_space (-7) /* Out of space in I/O MMU. */
627 #define GNTST_permission_denied (-8) /* Not enough privilege for operation. */
628 #define GNTST_bad_page (-9) /* Specified page was invalid for op. */
629 #define GNTST_bad_copy_arg (-10) /* copy arguments cross page boundary. */
630 #define GNTST_address_too_big (-11) /* transfer page address too large. */
631 #define GNTST_eagain (-12) /* Operation not done; try again. */
634 #define GNTTABOP_error_msgs { \
637 "unrecognised domain id", \
638 "invalid grant reference", \
639 "invalid mapping handle", \
640 "invalid virtual address", \
641 "invalid device address", \
642 "no spare translation slot in the I/O MMU", \
643 "permission denied", \
645 "copy arguments cross page boundary", \
646 "page address size too large", \
647 "operation not done; try again" \
650 #endif /* __XEN_PUBLIC_GRANT_TABLE_H__ */
658 * indent-tabs-mode: nil