grant_table.h revision 183340 
1/******************************************************************************
2 * grant_table.h
3 *
4 * Interface for granting foreign access to page frames, and receiving
5 * page-ownership transfers.
6 *
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:
13 *
14 * The above copyright notice and this permission notice shall be included in
15 * all copies or substantial portions of the Software.
16 *
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.
24 *
25 * Copyright (c) 2004, K A Fraser
26 */
27
28#ifndef __XEN_PUBLIC_GRANT_TABLE_H__
29#define __XEN_PUBLIC_GRANT_TABLE_H__
30
31
32/***********************************
33 * GRANT TABLE REPRESENTATION
34 */
35
36/* Some rough guidelines on accessing and updating grant-table entries
37 * in a concurrency-safe manner. For more information, Linux contains a
38 * reference implementation for guest OSes (arch/xen/kernel/grant_table.c).
39 *
40 * NB. WMB is a no-op on current-generation x86 processors. However, a
41 *     compiler barrier will still be required.
42 *
43 * Introducing a valid entry into the grant table:
44 *  1. Write ent->domid.
45 *  2. Write ent->frame:
46 *      GTF_permit_access:   Frame to which access is permitted.
47 *      GTF_accept_transfer: Pseudo-phys frame slot being filled by new
48 *                           frame, or zero if none.
49 *  3. Write memory barrier (WMB).
50 *  4. Write ent->flags, inc. valid type.
51 *
52 * Invalidating an unused GTF_permit_access entry:
53 *  1. flags = ent->flags.
54 *  2. Observe that !(flags & (GTF_reading|GTF_writing)).
55 *  3. Check result of SMP-safe CMPXCHG(&ent->flags, flags, 0).
56 *  NB. No need for WMB as reuse of entry is control-dependent on success of
57 *      step 3, and all architectures guarantee ordering of ctrl-dep writes.
58 *
59 * Invalidating an in-use GTF_permit_access entry:
60 *  This cannot be done directly. Request assistance from the domain controller
61 *  which can set a timeout on the use of a grant entry and take necessary
62 *  action. (NB. This is not yet implemented!).
63 *
64 * Invalidating an unused GTF_accept_transfer entry:
65 *  1. flags = ent->flags.
66 *  2. Observe that !(flags & GTF_transfer_committed). [*]
67 *  3. Check result of SMP-safe CMPXCHG(&ent->flags, flags, 0).
68 *  NB. No need for WMB as reuse of entry is control-dependent on success of
69 *      step 3, and all architectures guarantee ordering of ctrl-dep writes.
70 *  [*] If GTF_transfer_committed is set then the grant entry is 'committed'.
71 *      The guest must /not/ modify the grant entry until the address of the
72 *      transferred frame is written. It is safe for the guest to spin waiting
73 *      for this to occur (detect by observing GTF_transfer_completed in
74 *      ent->flags).
75 *
76 * Invalidating a committed GTF_accept_transfer entry:
77 *  1. Wait for (ent->flags & GTF_transfer_completed).
78 *
79 * Changing a GTF_permit_access from writable to read-only:
80 *  Use SMP-safe CMPXCHG to set GTF_readonly, while checking !GTF_writing.
81 *
82 * Changing a GTF_permit_access from read-only to writable:
83 *  Use SMP-safe bit-setting instruction.
84 */
85
86/*
87 * A grant table comprises a packed array of grant entries in one or more
88 * page frames shared between Xen and a guest.
89 * [XEN]: This field is written by Xen and read by the sharing guest.
90 * [GST]: This field is written by the guest and read by Xen.
91 */
92struct grant_entry {
93    /* GTF_xxx: various type and flag information.  [XEN,GST] */
94    uint16_t flags;
95    /* The domain being granted foreign privileges. [GST] */
96    domid_t  domid;
97    /*
98     * GTF_permit_access: Frame that @domid is allowed to map and access. [GST]
99     * GTF_accept_transfer: Frame whose ownership transferred by @domid. [XEN]
100     */
101    uint32_t frame;
102};
103typedef struct grant_entry grant_entry_t;
104
105/*
106 * Type of grant entry.
107 *  GTF_invalid: This grant entry grants no privileges.
108 *  GTF_permit_access: Allow @domid to map/access @frame.
109 *  GTF_accept_transfer: Allow @domid to transfer ownership of one page frame
110 *                       to this guest. Xen writes the page number to @frame.
111 */
112#define GTF_invalid         (0U<<0)
113#define GTF_permit_access   (1U<<0)
114#define GTF_accept_transfer (2U<<0)
115#define GTF_type_mask       (3U<<0)
116
117/*
118 * Subflags for GTF_permit_access.
119 *  GTF_readonly: Restrict @domid to read-only mappings and accesses. [GST]
120 *  GTF_reading: Grant entry is currently mapped for reading by @domid. [XEN]
121 *  GTF_writing: Grant entry is currently mapped for writing by @domid. [XEN]
122 *  GTF_PAT, GTF_PWT, GTF_PCD: (x86) cache attribute flags for the grant [GST]
123 */
124#define _GTF_readonly       (2)
125#define GTF_readonly        (1U<<_GTF_readonly)
126#define _GTF_reading        (3)
127#define GTF_reading         (1U<<_GTF_reading)
128#define _GTF_writing        (4)
129#define GTF_writing         (1U<<_GTF_writing)
130#define _GTF_PWT            (5)
131#define GTF_PWT             (1U<<_GTF_PWT)
132#define _GTF_PCD            (6)
133#define GTF_PCD             (1U<<_GTF_PCD)
134#define _GTF_PAT            (7)
135#define GTF_PAT             (1U<<_GTF_PAT)
136
137/*
138 * Subflags for GTF_accept_transfer:
139 *  GTF_transfer_committed: Xen sets this flag to indicate that it is committed
140 *      to transferring ownership of a page frame. When a guest sees this flag
141 *      it must /not/ modify the grant entry until GTF_transfer_completed is
142 *      set by Xen.
143 *  GTF_transfer_completed: It is safe for the guest to spin-wait on this flag
144 *      after reading GTF_transfer_committed. Xen will always write the frame
145 *      address, followed by ORing this flag, in a timely manner.
146 */
147#define _GTF_transfer_committed (2)
148#define GTF_transfer_committed  (1U<<_GTF_transfer_committed)
149#define _GTF_transfer_completed (3)
150#define GTF_transfer_completed  (1U<<_GTF_transfer_completed)
151
152
153/***********************************
154 * GRANT TABLE QUERIES AND USES
155 */
156
157/*
158 * Reference to a grant entry in a specified domain's grant table.
159 */
160typedef uint32_t grant_ref_t;
161
162/*
163 * Handle to track a mapping created via a grant reference.
164 */
165typedef uint32_t grant_handle_t;
166
167/*
168 * GNTTABOP_map_grant_ref: Map the grant entry (<dom>,<ref>) for access
169 * by devices and/or host CPUs. If successful, <handle> is a tracking number
170 * that must be presented later to destroy the mapping(s). On error, <handle>
171 * is a negative status code.
172 * NOTES:
173 *  1. If GNTMAP_device_map is specified then <dev_bus_addr> is the address
174 *     via which I/O devices may access the granted frame.
175 *  2. If GNTMAP_host_map is specified then a mapping will be added at
176 *     either a host virtual address in the current address space, or at
177 *     a PTE at the specified machine address.  The type of mapping to
178 *     perform is selected through the GNTMAP_contains_pte flag, and the
179 *     address is specified in <host_addr>.
180 *  3. Mappings should only be destroyed via GNTTABOP_unmap_grant_ref. If a
181 *     host mapping is destroyed by other means then it is *NOT* guaranteed
182 *     to be accounted to the correct grant reference!
183 */
184#define GNTTABOP_map_grant_ref        0
185struct gnttab_map_grant_ref {
186    /* IN parameters. */
187    uint64_t host_addr;
188    uint32_t flags;               /* GNTMAP_* */
189    grant_ref_t ref;
190    domid_t  dom;
191    /* OUT parameters. */
192    int16_t  status;              /* GNTST_* */
193    grant_handle_t handle;
194    uint64_t dev_bus_addr;
195};
196typedef struct gnttab_map_grant_ref gnttab_map_grant_ref_t;
197DEFINE_XEN_GUEST_HANDLE(gnttab_map_grant_ref_t);
198
199/*
200 * GNTTABOP_unmap_grant_ref: Destroy one or more grant-reference mappings
201 * tracked by <handle>. If <host_addr> or <dev_bus_addr> is zero, that
202 * field is ignored. If non-zero, they must refer to a device/host mapping
203 * that is tracked by <handle>
204 * NOTES:
205 *  1. The call may fail in an undefined manner if either mapping is not
206 *     tracked by <handle>.
207 *  3. After executing a batch of unmaps, it is guaranteed that no stale
208 *     mappings will remain in the device or host TLBs.
209 */
210#define GNTTABOP_unmap_grant_ref      1
211struct gnttab_unmap_grant_ref {
212    /* IN parameters. */
213    uint64_t host_addr;
214    uint64_t dev_bus_addr;
215    grant_handle_t handle;
216    /* OUT parameters. */
217    int16_t  status;              /* GNTST_* */
218};
219typedef struct gnttab_unmap_grant_ref gnttab_unmap_grant_ref_t;
220DEFINE_XEN_GUEST_HANDLE(gnttab_unmap_grant_ref_t);
221
222/*
223 * GNTTABOP_setup_table: Set up a grant table for <dom> comprising at least
224 * <nr_frames> pages. The frame addresses are written to the <frame_list>.
225 * Only <nr_frames> addresses are written, even if the table is larger.
226 * NOTES:
227 *  1. <dom> may be specified as DOMID_SELF.
228 *  2. Only a sufficiently-privileged domain may specify <dom> != DOMID_SELF.
229 *  3. Xen may not support more than a single grant-table page per domain.
230 */
231#define GNTTABOP_setup_table          2
232struct gnttab_setup_table {
233    /* IN parameters. */
234    domid_t  dom;
235    uint32_t nr_frames;
236    /* OUT parameters. */
237    int16_t  status;              /* GNTST_* */
238#ifdef __LP64__
239    XEN_GUEST_HANDLE(uint64_t) frame_list;
240#else
241    XEN_GUEST_HANDLE(uint32_t) frame_list;
242#endif
243};
244typedef struct gnttab_setup_table gnttab_setup_table_t;
245DEFINE_XEN_GUEST_HANDLE(gnttab_setup_table_t);
246
247/*
248 * GNTTABOP_dump_table: Dump the contents of the grant table to the
249 * xen console. Debugging use only.
250 */
251#define GNTTABOP_dump_table           3
252struct gnttab_dump_table {
253    /* IN parameters. */
254    domid_t dom;
255    /* OUT parameters. */
256    int16_t status;               /* GNTST_* */
257};
258typedef struct gnttab_dump_table gnttab_dump_table_t;
259DEFINE_XEN_GUEST_HANDLE(gnttab_dump_table_t);
260
261/*
262 * GNTTABOP_transfer_grant_ref: Transfer <frame> to a foreign domain. The
263 * foreign domain has previously registered its interest in the transfer via
264 * <domid, ref>.
265 *
266 * Note that, even if the transfer fails, the specified page no longer belongs
267 * to the calling domain *unless* the error is GNTST_bad_page.
268 */
269#define GNTTABOP_transfer                4
270struct gnttab_transfer {
271    /* IN parameters. */
272    xen_pfn_t     mfn;
273    domid_t       domid;
274    grant_ref_t   ref;
275    /* OUT parameters. */
276    int16_t       status;
277};
278typedef struct gnttab_transfer gnttab_transfer_t;
279DEFINE_XEN_GUEST_HANDLE(gnttab_transfer_t);
280
281
282/*
283 * GNTTABOP_copy: Hypervisor based copy
284 * source and destinations can be eithers MFNs or, for foreign domains,
285 * grant references. the foreign domain has to grant read/write access
286 * in its grant table.
287 *
288 * The flags specify what type source and destinations are (either MFN
289 * or grant reference).
290 *
291 * Note that this can also be used to copy data between two domains
292 * via a third party if the source and destination domains had previously
293 * grant appropriate access to their pages to the third party.
294 *
295 * source_offset specifies an offset in the source frame, dest_offset
296 * the offset in the target frame and  len specifies the number of
297 * bytes to be copied.
298 */
299
300#define _GNTCOPY_source_gref      (0)
301#define GNTCOPY_source_gref       (1<<_GNTCOPY_source_gref)
302#define _GNTCOPY_dest_gref        (1)
303#define GNTCOPY_dest_gref         (1<<_GNTCOPY_dest_gref)
304
305#define GNTTABOP_copy                 5
306typedef struct gnttab_copy {
307    /* IN parameters. */
308    struct {
309        union {
310            grant_ref_t ref;
311            xen_pfn_t   gmfn;
312        } u;
313        domid_t  domid;
314        uint16_t offset;
315    } source, dest;
316    uint16_t      len;
317    uint16_t      flags;          /* GNTCOPY_* */
318    /* OUT parameters. */
319    int16_t       status;
320} gnttab_copy_t;
321DEFINE_XEN_GUEST_HANDLE(gnttab_copy_t);
322
323/*
324 * GNTTABOP_query_size: Query the current and maximum sizes of the shared
325 * grant table.
326 * NOTES:
327 *  1. <dom> may be specified as DOMID_SELF.
328 *  2. Only a sufficiently-privileged domain may specify <dom> != DOMID_SELF.
329 */
330#define GNTTABOP_query_size           6
331struct gnttab_query_size {
332    /* IN parameters. */
333    domid_t  dom;
334    /* OUT parameters. */
335    uint32_t nr_frames;
336    uint32_t max_nr_frames;
337    int16_t  status;              /* GNTST_* */
338};
339typedef struct gnttab_query_size gnttab_query_size_t;
340DEFINE_XEN_GUEST_HANDLE(gnttab_query_size_t);
341
342/*
343 * GNTTABOP_unmap_and_replace: Destroy one or more grant-reference mappings
344 * tracked by <handle> but atomically replace the page table entry with one
345 * pointing to the machine address under <new_addr>.  <new_addr> will be
346 * redirected to the null entry.
347 * NOTES:
348 *  1. The call may fail in an undefined manner if either mapping is not
349 *     tracked by <handle>.
350 *  2. After executing a batch of unmaps, it is guaranteed that no stale
351 *     mappings will remain in the device or host TLBs.
352 */
353#define GNTTABOP_unmap_and_replace    7
354struct gnttab_unmap_and_replace {
355    /* IN parameters. */
356    uint64_t host_addr;
357    uint64_t new_addr;
358    grant_handle_t handle;
359    /* OUT parameters. */
360    int16_t  status;              /* GNTST_* */
361};
362typedef struct gnttab_unmap_and_replace gnttab_unmap_and_replace_t;
363DEFINE_XEN_GUEST_HANDLE(gnttab_unmap_and_replace_t);
364
365
366/*
367 * Bitfield values for update_pin_status.flags.
368 */
369 /* Map the grant entry for access by I/O devices. */
370#define _GNTMAP_device_map      (0)
371#define GNTMAP_device_map       (1<<_GNTMAP_device_map)
372 /* Map the grant entry for access by host CPUs. */
373#define _GNTMAP_host_map        (1)
374#define GNTMAP_host_map         (1<<_GNTMAP_host_map)
375 /* Accesses to the granted frame will be restricted to read-only access. */
376#define _GNTMAP_readonly        (2)
377#define GNTMAP_readonly         (1<<_GNTMAP_readonly)
378 /*
379  * GNTMAP_host_map subflag:
380  *  0 => The host mapping is usable only by the guest OS.
381  *  1 => The host mapping is usable by guest OS + current application.
382  */
383#define _GNTMAP_application_map (3)
384#define GNTMAP_application_map  (1<<_GNTMAP_application_map)
385
386 /*
387  * GNTMAP_contains_pte subflag:
388  *  0 => This map request contains a host virtual address.
389  *  1 => This map request contains the machine addess of the PTE to update.
390  */
391#define _GNTMAP_contains_pte    (4)
392#define GNTMAP_contains_pte     (1<<_GNTMAP_contains_pte)
393
394/*
395 * Values for error status returns. All errors are -ve.
396 */
397#define GNTST_okay             (0)  /* Normal return.                        */
398#define GNTST_general_error    (-1) /* General undefined error.              */
399#define GNTST_bad_domain       (-2) /* Unrecognsed domain id.                */
400#define GNTST_bad_gntref       (-3) /* Unrecognised or inappropriate gntref. */
401#define GNTST_bad_handle       (-4) /* Unrecognised or inappropriate handle. */
402#define GNTST_bad_virt_addr    (-5) /* Inappropriate virtual address to map. */
403#define GNTST_bad_dev_addr     (-6) /* Inappropriate device address to unmap.*/
404#define GNTST_no_device_space  (-7) /* Out of space in I/O MMU.              */
405#define GNTST_permission_denied (-8) /* Not enough privilege for operation.  */
406#define GNTST_bad_page         (-9) /* Specified page was invalid for op.    */
407#define GNTST_bad_copy_arg    (-10) /* copy arguments cross page boundary.   */
408#define GNTST_address_too_big (-11) /* transfer page address too large.      */
409
410#define GNTTABOP_error_msgs {                   \
411    "okay",                                     \
412    "undefined error",                          \
413    "unrecognised domain id",                   \
414    "invalid grant reference",                  \
415    "invalid mapping handle",                   \
416    "invalid virtual address",                  \
417    "invalid device address",                   \
418    "no spare translation slot in the I/O MMU", \
419    "permission denied",                        \
420    "bad page",                                 \
421    "copy arguments cross page boundary",       \
422    "page address size too large"               \
423}
424
425#endif /* __XEN_PUBLIC_GRANT_TABLE_H__ */
426
427/*
428 * Local variables:
429 * mode: C
430 * c-set-style: "BSD"
431 * c-basic-offset: 4
432 * tab-width: 4
433 * indent-tabs-mode: nil
434 * End:
435 */
436