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__
36 * `incontents 150 gnttab Grant Tables
38 * Xen's grant tables provide a generic mechanism to memory sharing
39 * between domains. This shared memory interface underpins the split
40 * device drivers for block and network IO.
42 * Each domain has its own grant table. This is a data structure that
43 * is shared with Xen; it allows the domain to tell Xen what kind of
44 * permissions other domains have on its pages. Entries in the grant
45 * table are identified by grant references. A grant reference is an
46 * integer, which indexes into the grant table. It acts as a
47 * capability which the grantee can use to perform operations on the
50 * This capability-based system allows shared-memory communications
51 * between unprivileged domains. A grant reference also encapsulates
52 * the details of a shared page, removing the need for a domain to
53 * know the real machine address of a page it is sharing. This makes
54 * it possible to share memory correctly with domains running in
55 * fully virtualised memory.
58 /***********************************
59 * GRANT TABLE REPRESENTATION
62 /* Some rough guidelines on accessing and updating grant-table entries
63 * in a concurrency-safe manner. For more information, Linux contains a
64 * reference implementation for guest OSes (drivers/xen/grant_table.c, see
65 * http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=blob;f=drivers/xen/grant-table.c;hb=HEAD
67 * NB. WMB is a no-op on current-generation x86 processors. However, a
68 * compiler barrier will still be required.
70 * Introducing a valid entry into the grant table:
71 * 1. Write ent->domid.
72 * 2. Write ent->frame:
73 * GTF_permit_access: Frame to which access is permitted.
74 * GTF_accept_transfer: Pseudo-phys frame slot being filled by new
75 * frame, or zero if none.
76 * 3. Write memory barrier (WMB).
77 * 4. Write ent->flags, inc. valid type.
79 * Invalidating an unused GTF_permit_access entry:
80 * 1. flags = ent->flags.
81 * 2. Observe that !(flags & (GTF_reading|GTF_writing)).
82 * 3. Check result of SMP-safe CMPXCHG(&ent->flags, flags, 0).
83 * NB. No need for WMB as reuse of entry is control-dependent on success of
84 * step 3, and all architectures guarantee ordering of ctrl-dep writes.
86 * Invalidating an in-use GTF_permit_access entry:
87 * This cannot be done directly. Request assistance from the domain controller
88 * which can set a timeout on the use of a grant entry and take necessary
89 * action. (NB. This is not yet implemented!).
91 * Invalidating an unused GTF_accept_transfer entry:
92 * 1. flags = ent->flags.
93 * 2. Observe that !(flags & GTF_transfer_committed). [*]
94 * 3. Check result of SMP-safe CMPXCHG(&ent->flags, flags, 0).
95 * NB. No need for WMB as reuse of entry is control-dependent on success of
96 * step 3, and all architectures guarantee ordering of ctrl-dep writes.
97 * [*] If GTF_transfer_committed is set then the grant entry is 'committed'.
98 * The guest must /not/ modify the grant entry until the address of the
99 * transferred frame is written. It is safe for the guest to spin waiting
100 * for this to occur (detect by observing GTF_transfer_completed in
103 * Invalidating a committed GTF_accept_transfer entry:
104 * 1. Wait for (ent->flags & GTF_transfer_completed).
106 * Changing a GTF_permit_access from writable to read-only:
107 * Use SMP-safe CMPXCHG to set GTF_readonly, while checking !GTF_writing.
109 * Changing a GTF_permit_access from read-only to writable:
110 * Use SMP-safe bit-setting instruction.
114 * Reference to a grant entry in a specified domain's grant table.
116 typedef uint32_t grant_ref_t;
119 * A grant table comprises a packed array of grant entries in one or more
120 * page frames shared between Xen and a guest.
121 * [XEN]: This field is written by Xen and read by the sharing guest.
122 * [GST]: This field is written by the guest and read by Xen.
126 * Version 1 of the grant table entry structure is maintained purely
127 * for backwards compatibility. New guests should use version 2.
129 #if __XEN_INTERFACE_VERSION__ < 0x0003020a
130 #define grant_entry_v1 grant_entry
131 #define grant_entry_v1_t grant_entry_t
133 struct grant_entry_v1 {
134 /* GTF_xxx: various type and flag information. [XEN,GST] */
136 /* The domain being granted foreign privileges. [GST] */
139 * GTF_permit_access: Frame that @domid is allowed to map and access. [GST]
140 * GTF_accept_transfer: Frame whose ownership transferred by @domid. [XEN]
144 typedef struct grant_entry_v1 grant_entry_v1_t;
146 /* The first few grant table entries will be preserved across grant table
147 * version changes and may be pre-populated at domain creation by tools.
149 #define GNTTAB_NR_RESERVED_ENTRIES 8
150 #define GNTTAB_RESERVED_CONSOLE 0
151 #define GNTTAB_RESERVED_XENSTORE 1
154 * Type of grant entry.
155 * GTF_invalid: This grant entry grants no privileges.
156 * GTF_permit_access: Allow @domid to map/access @frame.
157 * GTF_accept_transfer: Allow @domid to transfer ownership of one page frame
158 * to this guest. Xen writes the page number to @frame.
159 * GTF_transitive: Allow @domid to transitively access a subrange of
160 * @trans_grant in @trans_domid. No mappings are allowed.
162 #define GTF_invalid (0U<<0)
163 #define GTF_permit_access (1U<<0)
164 #define GTF_accept_transfer (2U<<0)
165 #define GTF_transitive (3U<<0)
166 #define GTF_type_mask (3U<<0)
169 * Subflags for GTF_permit_access.
170 * GTF_readonly: Restrict @domid to read-only mappings and accesses. [GST]
171 * GTF_reading: Grant entry is currently mapped for reading by @domid. [XEN]
172 * GTF_writing: Grant entry is currently mapped for writing by @domid. [XEN]
173 * GTF_PAT, GTF_PWT, GTF_PCD: (x86) cache attribute flags for the grant [GST]
174 * GTF_sub_page: Grant access to only a subrange of the page. @domid
175 * will only be allowed to copy from the grant, and not
178 #define _GTF_readonly (2)
179 #define GTF_readonly (1U<<_GTF_readonly)
180 #define _GTF_reading (3)
181 #define GTF_reading (1U<<_GTF_reading)
182 #define _GTF_writing (4)
183 #define GTF_writing (1U<<_GTF_writing)
185 #define GTF_PWT (1U<<_GTF_PWT)
187 #define GTF_PCD (1U<<_GTF_PCD)
189 #define GTF_PAT (1U<<_GTF_PAT)
190 #define _GTF_sub_page (8)
191 #define GTF_sub_page (1U<<_GTF_sub_page)
194 * Subflags for GTF_accept_transfer:
195 * GTF_transfer_committed: Xen sets this flag to indicate that it is committed
196 * to transferring ownership of a page frame. When a guest sees this flag
197 * it must /not/ modify the grant entry until GTF_transfer_completed is
199 * GTF_transfer_completed: It is safe for the guest to spin-wait on this flag
200 * after reading GTF_transfer_committed. Xen will always write the frame
201 * address, followed by ORing this flag, in a timely manner.
203 #define _GTF_transfer_committed (2)
204 #define GTF_transfer_committed (1U<<_GTF_transfer_committed)
205 #define _GTF_transfer_completed (3)
206 #define GTF_transfer_completed (1U<<_GTF_transfer_completed)
209 * Version 2 grant table entries. These fulfil the same role as
210 * version 1 entries, but can represent more complicated operations.
211 * Any given domain will have either a version 1 or a version 2 table,
212 * and every entry in the table will be the same version.
214 * The interface by which domains use grant references does not depend
215 * on the grant table version in use by the other domain.
217 #if __XEN_INTERFACE_VERSION__ >= 0x0003020a
219 * Version 1 and version 2 grant entries share a common prefix. The
220 * fields of the prefix are documented as part of struct
223 struct grant_entry_header {
227 typedef struct grant_entry_header grant_entry_header_t;
230 * Version 2 of the grant entry structure.
232 union grant_entry_v2 {
233 grant_entry_header_t hdr;
236 * This member is used for V1-style full page grants, where either:
238 * -- hdr.type is GTF_accept_transfer, or
239 * -- hdr.type is GTF_permit_access and GTF_sub_page is not set.
241 * In that case, the frame field has the same semantics as the
242 * field of the same name in the V1 entry structure.
245 grant_entry_header_t hdr;
251 * If the grant type is GTF_grant_access and GTF_sub_page is set,
252 * @domid is allowed to access bytes [@page_off,@page_off+@length)
256 grant_entry_header_t hdr;
263 * If the grant is GTF_transitive, @domid is allowed to use the
264 * grant @gref in domain @trans_domid, as if it was the local
265 * domain. Obviously, the transitive access must be compatible
266 * with the original grant.
268 * The current version of Xen does not allow transitive grants
272 grant_entry_header_t hdr;
278 uint32_t __spacer[4]; /* Pad to a power of two */
280 typedef union grant_entry_v2 grant_entry_v2_t;
282 typedef uint16_t grant_status_t;
284 #endif /* __XEN_INTERFACE_VERSION__ */
286 /***********************************
287 * GRANT TABLE QUERIES AND USES
290 /* ` enum neg_errnoval
291 * ` HYPERVISOR_grant_table_op(enum grant_table_op cmd,
293 * ` unsigned int count)
296 * @args points to an array of a per-command data structure. The array
300 /* ` enum grant_table_op { // GNTTABOP_* => struct gnttab_* */
301 #define GNTTABOP_map_grant_ref 0
302 #define GNTTABOP_unmap_grant_ref 1
303 #define GNTTABOP_setup_table 2
304 #define GNTTABOP_dump_table 3
305 #define GNTTABOP_transfer 4
306 #define GNTTABOP_copy 5
307 #define GNTTABOP_query_size 6
308 #define GNTTABOP_unmap_and_replace 7
309 #if __XEN_INTERFACE_VERSION__ >= 0x0003020a
310 #define GNTTABOP_set_version 8
311 #define GNTTABOP_get_status_frames 9
312 #define GNTTABOP_get_version 10
313 #define GNTTABOP_swap_grant_ref 11
314 #endif /* __XEN_INTERFACE_VERSION__ */
318 * Handle to track a mapping created via a grant reference.
320 typedef uint32_t grant_handle_t;
323 * GNTTABOP_map_grant_ref: Map the grant entry (<dom>,<ref>) for access
324 * by devices and/or host CPUs. If successful, <handle> is a tracking number
325 * that must be presented later to destroy the mapping(s). On error, <handle>
326 * is a negative status code.
328 * 1. If GNTMAP_device_map is specified then <dev_bus_addr> is the address
329 * via which I/O devices may access the granted frame.
330 * 2. If GNTMAP_host_map is specified then a mapping will be added at
331 * either a host virtual address in the current address space, or at
332 * a PTE at the specified machine address. The type of mapping to
333 * perform is selected through the GNTMAP_contains_pte flag, and the
334 * address is specified in <host_addr>.
335 * 3. Mappings should only be destroyed via GNTTABOP_unmap_grant_ref. If a
336 * host mapping is destroyed by other means then it is *NOT* guaranteed
337 * to be accounted to the correct grant reference!
339 struct gnttab_map_grant_ref {
342 uint32_t flags; /* GNTMAP_* */
345 /* OUT parameters. */
346 int16_t status; /* => enum grant_status */
347 grant_handle_t handle;
348 uint64_t dev_bus_addr;
350 typedef struct gnttab_map_grant_ref gnttab_map_grant_ref_t;
351 DEFINE_XEN_GUEST_HANDLE(gnttab_map_grant_ref_t);
354 * GNTTABOP_unmap_grant_ref: Destroy one or more grant-reference mappings
355 * tracked by <handle>. If <host_addr> or <dev_bus_addr> is zero, that
356 * field is ignored. If non-zero, they must refer to a device/host mapping
357 * that is tracked by <handle>
359 * 1. The call may fail in an undefined manner if either mapping is not
360 * tracked by <handle>.
361 * 3. After executing a batch of unmaps, it is guaranteed that no stale
362 * mappings will remain in the device or host TLBs.
364 struct gnttab_unmap_grant_ref {
367 uint64_t dev_bus_addr;
368 grant_handle_t handle;
369 /* OUT parameters. */
370 int16_t status; /* => enum grant_status */
372 typedef struct gnttab_unmap_grant_ref gnttab_unmap_grant_ref_t;
373 DEFINE_XEN_GUEST_HANDLE(gnttab_unmap_grant_ref_t);
376 * GNTTABOP_setup_table: Set up a grant table for <dom> comprising at least
377 * <nr_frames> pages. The frame addresses are written to the <frame_list>.
378 * Only <nr_frames> addresses are written, even if the table is larger.
380 * 1. <dom> may be specified as DOMID_SELF.
381 * 2. Only a sufficiently-privileged domain may specify <dom> != DOMID_SELF.
382 * 3. Xen may not support more than a single grant-table page per domain.
384 struct gnttab_setup_table {
388 /* OUT parameters. */
389 int16_t status; /* => enum grant_status */
390 #if __XEN_INTERFACE_VERSION__ < 0x00040300
391 XEN_GUEST_HANDLE(ulong) frame_list;
393 XEN_GUEST_HANDLE(xen_pfn_t) frame_list;
396 typedef struct gnttab_setup_table gnttab_setup_table_t;
397 DEFINE_XEN_GUEST_HANDLE(gnttab_setup_table_t);
400 * GNTTABOP_dump_table: Dump the contents of the grant table to the
401 * xen console. Debugging use only.
403 struct gnttab_dump_table {
406 /* OUT parameters. */
407 int16_t status; /* => enum grant_status */
409 typedef struct gnttab_dump_table gnttab_dump_table_t;
410 DEFINE_XEN_GUEST_HANDLE(gnttab_dump_table_t);
413 * GNTTABOP_transfer_grant_ref: Transfer <frame> to a foreign domain. The
414 * foreign domain has previously registered its interest in the transfer via
417 * Note that, even if the transfer fails, the specified page no longer belongs
418 * to the calling domain *unless* the error is GNTST_bad_page.
420 struct gnttab_transfer {
425 /* OUT parameters. */
428 typedef struct gnttab_transfer gnttab_transfer_t;
429 DEFINE_XEN_GUEST_HANDLE(gnttab_transfer_t);
433 * GNTTABOP_copy: Hypervisor based copy
434 * source and destinations can be eithers MFNs or, for foreign domains,
435 * grant references. the foreign domain has to grant read/write access
436 * in its grant table.
438 * The flags specify what type source and destinations are (either MFN
439 * or grant reference).
441 * Note that this can also be used to copy data between two domains
442 * via a third party if the source and destination domains had previously
443 * grant appropriate access to their pages to the third party.
445 * source_offset specifies an offset in the source frame, dest_offset
446 * the offset in the target frame and len specifies the number of
447 * bytes to be copied.
450 #define _GNTCOPY_source_gref (0)
451 #define GNTCOPY_source_gref (1<<_GNTCOPY_source_gref)
452 #define _GNTCOPY_dest_gref (1)
453 #define GNTCOPY_dest_gref (1<<_GNTCOPY_dest_gref)
466 uint16_t flags; /* GNTCOPY_* */
467 /* OUT parameters. */
470 typedef struct gnttab_copy gnttab_copy_t;
471 DEFINE_XEN_GUEST_HANDLE(gnttab_copy_t);
474 * GNTTABOP_query_size: Query the current and maximum sizes of the shared
477 * 1. <dom> may be specified as DOMID_SELF.
478 * 2. Only a sufficiently-privileged domain may specify <dom> != DOMID_SELF.
480 struct gnttab_query_size {
483 /* OUT parameters. */
485 uint32_t max_nr_frames;
486 int16_t status; /* => enum grant_status */
488 typedef struct gnttab_query_size gnttab_query_size_t;
489 DEFINE_XEN_GUEST_HANDLE(gnttab_query_size_t);
492 * GNTTABOP_unmap_and_replace: Destroy one or more grant-reference mappings
493 * tracked by <handle> but atomically replace the page table entry with one
494 * pointing to the machine address under <new_addr>. <new_addr> will be
495 * redirected to the null entry.
497 * 1. The call may fail in an undefined manner if either mapping is not
498 * tracked by <handle>.
499 * 2. After executing a batch of unmaps, it is guaranteed that no stale
500 * mappings will remain in the device or host TLBs.
502 struct gnttab_unmap_and_replace {
506 grant_handle_t handle;
507 /* OUT parameters. */
508 int16_t status; /* => enum grant_status */
510 typedef struct gnttab_unmap_and_replace gnttab_unmap_and_replace_t;
511 DEFINE_XEN_GUEST_HANDLE(gnttab_unmap_and_replace_t);
513 #if __XEN_INTERFACE_VERSION__ >= 0x0003020a
515 * GNTTABOP_set_version: Request a particular version of the grant
516 * table shared table structure. This operation can only be performed
517 * once in any given domain. It must be performed before any grants
518 * are activated; otherwise, the domain will be stuck with version 1.
519 * The only defined versions are 1 and 2.
521 struct gnttab_set_version {
522 /* IN/OUT parameters */
525 typedef struct gnttab_set_version gnttab_set_version_t;
526 DEFINE_XEN_GUEST_HANDLE(gnttab_set_version_t);
530 * GNTTABOP_get_status_frames: Get the list of frames used to store grant
531 * status for <dom>. In grant format version 2, the status is separated
532 * from the other shared grant fields to allow more efficient synchronization
533 * using barriers instead of atomic cmpexch operations.
534 * <nr_frames> specify the size of vector <frame_list>.
535 * The frame addresses are returned in the <frame_list>.
536 * Only <nr_frames> addresses are returned, even if the table is larger.
538 * 1. <dom> may be specified as DOMID_SELF.
539 * 2. Only a sufficiently-privileged domain may specify <dom> != DOMID_SELF.
541 struct gnttab_get_status_frames {
545 /* OUT parameters. */
546 int16_t status; /* => enum grant_status */
547 XEN_GUEST_HANDLE(uint64_t) frame_list;
549 typedef struct gnttab_get_status_frames gnttab_get_status_frames_t;
550 DEFINE_XEN_GUEST_HANDLE(gnttab_get_status_frames_t);
553 * GNTTABOP_get_version: Get the grant table version which is in
554 * effect for domain <dom>.
556 struct gnttab_get_version {
563 typedef struct gnttab_get_version gnttab_get_version_t;
564 DEFINE_XEN_GUEST_HANDLE(gnttab_get_version_t);
567 * GNTTABOP_swap_grant_ref: Swap the contents of two grant entries.
569 struct gnttab_swap_grant_ref {
574 int16_t status; /* => enum grant_status */
576 typedef struct gnttab_swap_grant_ref gnttab_swap_grant_ref_t;
577 DEFINE_XEN_GUEST_HANDLE(gnttab_swap_grant_ref_t);
579 #endif /* __XEN_INTERFACE_VERSION__ */
582 * Bitfield values for gnttab_map_grant_ref.flags.
584 /* Map the grant entry for access by I/O devices. */
585 #define _GNTMAP_device_map (0)
586 #define GNTMAP_device_map (1<<_GNTMAP_device_map)
587 /* Map the grant entry for access by host CPUs. */
588 #define _GNTMAP_host_map (1)
589 #define GNTMAP_host_map (1<<_GNTMAP_host_map)
590 /* Accesses to the granted frame will be restricted to read-only access. */
591 #define _GNTMAP_readonly (2)
592 #define GNTMAP_readonly (1<<_GNTMAP_readonly)
594 * GNTMAP_host_map subflag:
595 * 0 => The host mapping is usable only by the guest OS.
596 * 1 => The host mapping is usable by guest OS + current application.
598 #define _GNTMAP_application_map (3)
599 #define GNTMAP_application_map (1<<_GNTMAP_application_map)
602 * GNTMAP_contains_pte subflag:
603 * 0 => This map request contains a host virtual address.
604 * 1 => This map request contains the machine addess of the PTE to update.
606 #define _GNTMAP_contains_pte (4)
607 #define GNTMAP_contains_pte (1<<_GNTMAP_contains_pte)
609 #define _GNTMAP_can_fail (5)
610 #define GNTMAP_can_fail (1<<_GNTMAP_can_fail)
613 * Bits to be placed in guest kernel available PTE bits (architecture
614 * dependent; only supported when XENFEAT_gnttab_map_avail_bits is set).
616 #define _GNTMAP_guest_avail0 (16)
617 #define GNTMAP_guest_avail_mask ((uint32_t)~0 << _GNTMAP_guest_avail0)
620 * Values for error status returns. All errors are -ve.
622 /* ` enum grant_status { */
623 #define GNTST_okay (0) /* Normal return. */
624 #define GNTST_general_error (-1) /* General undefined error. */
625 #define GNTST_bad_domain (-2) /* Unrecognsed domain id. */
626 #define GNTST_bad_gntref (-3) /* Unrecognised or inappropriate gntref. */
627 #define GNTST_bad_handle (-4) /* Unrecognised or inappropriate handle. */
628 #define GNTST_bad_virt_addr (-5) /* Inappropriate virtual address to map. */
629 #define GNTST_bad_dev_addr (-6) /* Inappropriate device address to unmap.*/
630 #define GNTST_no_device_space (-7) /* Out of space in I/O MMU. */
631 #define GNTST_permission_denied (-8) /* Not enough privilege for operation. */
632 #define GNTST_bad_page (-9) /* Specified page was invalid for op. */
633 #define GNTST_bad_copy_arg (-10) /* copy arguments cross page boundary. */
634 #define GNTST_address_too_big (-11) /* transfer page address too large. */
635 #define GNTST_eagain (-12) /* Operation not done; try again. */
638 #define GNTTABOP_error_msgs { \
641 "unrecognised domain id", \
642 "invalid grant reference", \
643 "invalid mapping handle", \
644 "invalid virtual address", \
645 "invalid device address", \
646 "no spare translation slot in the I/O MMU", \
647 "permission denied", \
649 "copy arguments cross page boundary", \
650 "page address size too large", \
651 "operation not done; try again" \
654 #endif /* __XEN_PUBLIC_GRANT_TABLE_H__ */
659 * c-file-style: "BSD"
662 * indent-tabs-mode: nil