grant_table.h revision 6144:5a5f883be4e5 
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 */
123#define _GTF_readonly       (2)
124#define GTF_readonly        (1U<<_GTF_readonly)
125#define _GTF_reading        (3)
126#define GTF_reading         (1U<<_GTF_reading)
127#define _GTF_writing        (4)
128#define GTF_writing         (1U<<_GTF_writing)
129
130/*
131 * Subflags for GTF_accept_transfer:
132 *  GTF_transfer_committed: Xen sets this flag to indicate that it is committed
133 *      to transferring ownership of a page frame. When a guest sees this flag
134 *      it must /not/ modify the grant entry until GTF_transfer_completed is
135 *      set by Xen.
136 *  GTF_transfer_completed: It is safe for the guest to spin-wait on this flag
137 *      after reading GTF_transfer_committed. Xen will always write the frame
138 *      address, followed by ORing this flag, in a timely manner.
139 */
140#define _GTF_transfer_committed (2)
141#define GTF_transfer_committed  (1U<<_GTF_transfer_committed)
142#define _GTF_transfer_completed (3)
143#define GTF_transfer_completed  (1U<<_GTF_transfer_completed)
144
145
146/***********************************
147 * GRANT TABLE QUERIES AND USES
148 */
149
150/*
151 * Reference to a grant entry in a specified domain's grant table.
152 */
153typedef uint32_t grant_ref_t;
154
155/*
156 * Handle to track a mapping created via a grant reference.
157 */
158typedef uint32_t grant_handle_t;
159
160/*
161 * GNTTABOP_map_grant_ref: Map the grant entry (<dom>,<ref>) for access
162 * by devices and/or host CPUs. If successful, <handle> is a tracking number
163 * that must be presented later to destroy the mapping(s). On error, <handle>
164 * is a negative status code.
165 * NOTES:
166 *  1. If GNTMAP_device_map is specified then <dev_bus_addr> is the address
167 *     via which I/O devices may access the granted frame.
168 *  2. If GNTMAP_host_map is specified then a mapping will be added at
169 *     either a host virtual address in the current address space, or at
170 *     a PTE at the specified machine address.  The type of mapping to
171 *     perform is selected through the GNTMAP_contains_pte flag, and the
172 *     address is specified in <host_addr>.
173 *  3. Mappings should only be destroyed via GNTTABOP_unmap_grant_ref. If a
174 *     host mapping is destroyed by other means then it is *NOT* guaranteed
175 *     to be accounted to the correct grant reference!
176 */
177#define GNTTABOP_map_grant_ref        0
178struct gnttab_map_grant_ref {
179    /* IN parameters. */
180    uint64_t host_addr;
181    uint32_t flags;               /* GNTMAP_* */
182    grant_ref_t ref;
183    domid_t  dom;
184    /* OUT parameters. */
185    int16_t  status;              /* GNTST_* */
186    grant_handle_t handle;
187    uint64_t dev_bus_addr;
188};
189typedef struct gnttab_map_grant_ref gnttab_map_grant_ref_t;
190DEFINE_XEN_GUEST_HANDLE(gnttab_map_grant_ref_t);
191
192/*
193 * GNTTABOP_unmap_grant_ref: Destroy one or more grant-reference mappings
194 * tracked by <handle>. If <host_addr> or <dev_bus_addr> is zero, that
195 * field is ignored. If non-zero, they must refer to a device/host mapping
196 * that is tracked by <handle>
197 * NOTES:
198 *  1. The call may fail in an undefined manner if either mapping is not
199 *     tracked by <handle>.
200 *  3. After executing a batch of unmaps, it is guaranteed that no stale
201 *     mappings will remain in the device or host TLBs.
202 */
203#define GNTTABOP_unmap_grant_ref      1
204struct gnttab_unmap_grant_ref {
205    /* IN parameters. */
206    uint64_t host_addr;
207    uint64_t dev_bus_addr;
208    grant_handle_t handle;
209    /* OUT parameters. */
210    int16_t  status;              /* GNTST_* */
211};
212typedef struct gnttab_unmap_grant_ref gnttab_unmap_grant_ref_t;
213DEFINE_XEN_GUEST_HANDLE(gnttab_unmap_grant_ref_t);
214
215/*
216 * GNTTABOP_setup_table: Set up a grant table for <dom> comprising at least
217 * <nr_frames> pages. The frame addresses are written to the <frame_list>.
218 * Only <nr_frames> addresses are written, even if the table is larger.
219 * NOTES:
220 *  1. <dom> may be specified as DOMID_SELF.
221 *  2. Only a sufficiently-privileged domain may specify <dom> != DOMID_SELF.
222 *  3. Xen may not support more than a single grant-table page per domain.
223 */
224#define GNTTABOP_setup_table          2
225struct gnttab_setup_table {
226    /* IN parameters. */
227    domid_t  dom;
228    uint32_t nr_frames;
229    /* OUT parameters. */
230    int16_t  status;              /* GNTST_* */
231    XEN_GUEST_HANDLE(ulong) frame_list;
232};
233typedef struct gnttab_setup_table gnttab_setup_table_t;
234DEFINE_XEN_GUEST_HANDLE(gnttab_setup_table_t);
235
236/*
237 * GNTTABOP_dump_table: Dump the contents of the grant table to the
238 * xen console. Debugging use only.
239 */
240#define GNTTABOP_dump_table           3
241struct gnttab_dump_table {
242    /* IN parameters. */
243    domid_t dom;
244    /* OUT parameters. */
245    int16_t status;               /* GNTST_* */
246};
247typedef struct gnttab_dump_table gnttab_dump_table_t;
248DEFINE_XEN_GUEST_HANDLE(gnttab_dump_table_t);
249
250/*
251 * GNTTABOP_transfer_grant_ref: Transfer <frame> to a foreign domain. The
252 * foreign domain has previously registered its interest in the transfer via
253 * <domid, ref>.
254 *
255 * Note that, even if the transfer fails, the specified page no longer belongs
256 * to the calling domain *unless* the error is GNTST_bad_page.
257 */
258#define GNTTABOP_transfer                4
259struct gnttab_transfer {
260    /* IN parameters. */
261    xen_pfn_t     mfn;
262    domid_t       domid;
263    grant_ref_t   ref;
264    /* OUT parameters. */
265    int16_t       status;
266};
267typedef struct gnttab_transfer gnttab_transfer_t;
268DEFINE_XEN_GUEST_HANDLE(gnttab_transfer_t);
269
270
271/*
272 * GNTTABOP_copy: Hypervisor based copy
273 * source and destinations can be eithers MFNs or, for foreign domains,
274 * grant references. the foreign domain has to grant read/write access
275 * in its grant table.
276 *
277 * The flags specify what type source and destinations are (either MFN
278 * or grant reference).
279 *
280 * Note that this can also be used to copy data between two domains
281 * via a third party if the source and destination domains had previously
282 * grant appropriate access to their pages to the third party.
283 *
284 * source_offset specifies an offset in the source frame, dest_offset
285 * the offset in the target frame and  len specifies the number of
286 * bytes to be copied.
287 */
288
289#define _GNTCOPY_source_gref      (0)
290#define GNTCOPY_source_gref       (1<<_GNTCOPY_source_gref)
291#define _GNTCOPY_dest_gref        (1)
292#define GNTCOPY_dest_gref         (1<<_GNTCOPY_dest_gref)
293
294#define GNTTABOP_copy                 5
295typedef struct gnttab_copy {
296    /* IN parameters. */
297    struct {
298        union {
299            grant_ref_t ref;
300            xen_pfn_t   gmfn;
301        } u;
302        domid_t  domid;
303        uint16_t offset;
304    } source, dest;
305    uint16_t      len;
306    uint16_t      flags;          /* GNTCOPY_* */
307    /* OUT parameters. */
308    int16_t       status;
309} gnttab_copy_t;
310DEFINE_XEN_GUEST_HANDLE(gnttab_copy_t);
311
312/*
313 * GNTTABOP_query_size: Query the current and maximum sizes of the shared
314 * grant table.
315 * NOTES:
316 *  1. <dom> may be specified as DOMID_SELF.
317 *  2. Only a sufficiently-privileged domain may specify <dom> != DOMID_SELF.
318 */
319#define GNTTABOP_query_size           6
320struct gnttab_query_size {
321    /* IN parameters. */
322    domid_t  dom;
323    /* OUT parameters. */
324    uint32_t nr_frames;
325    uint32_t max_nr_frames;
326    int16_t  status;              /* GNTST_* */
327};
328typedef struct gnttab_query_size gnttab_query_size_t;
329DEFINE_XEN_GUEST_HANDLE(gnttab_query_size_t);
330
331
332/*
333 * Bitfield values for update_pin_status.flags.
334 */
335 /* Map the grant entry for access by I/O devices. */
336#define _GNTMAP_device_map      (0)
337#define GNTMAP_device_map       (1<<_GNTMAP_device_map)
338 /* Map the grant entry for access by host CPUs. */
339#define _GNTMAP_host_map        (1)
340#define GNTMAP_host_map         (1<<_GNTMAP_host_map)
341 /* Accesses to the granted frame will be restricted to read-only access. */
342#define _GNTMAP_readonly        (2)
343#define GNTMAP_readonly         (1<<_GNTMAP_readonly)
344 /*
345  * GNTMAP_host_map subflag:
346  *  0 => The host mapping is usable only by the guest OS.
347  *  1 => The host mapping is usable by guest OS + current application.
348  */
349#define _GNTMAP_application_map (3)
350#define GNTMAP_application_map  (1<<_GNTMAP_application_map)
351
352 /*
353  * GNTMAP_contains_pte subflag:
354  *  0 => This map request contains a host virtual address.
355  *  1 => This map request contains the machine addess of the PTE to update.
356  */
357#define _GNTMAP_contains_pte    (4)
358#define GNTMAP_contains_pte     (1<<_GNTMAP_contains_pte)
359
360/*
361 * Values for error status returns. All errors are -ve.
362 */
363#define GNTST_okay             (0)  /* Normal return.                        */
364#define GNTST_general_error    (-1) /* General undefined error.              */
365#define GNTST_bad_domain       (-2) /* Unrecognsed domain id.                */
366#define GNTST_bad_gntref       (-3) /* Unrecognised or inappropriate gntref. */
367#define GNTST_bad_handle       (-4) /* Unrecognised or inappropriate handle. */
368#define GNTST_bad_virt_addr    (-5) /* Inappropriate virtual address to map. */
369#define GNTST_bad_dev_addr     (-6) /* Inappropriate device address to unmap.*/
370#define GNTST_no_device_space  (-7) /* Out of space in I/O MMU.              */
371#define GNTST_permission_denied (-8) /* Not enough privilege for operation.  */
372#define GNTST_bad_page         (-9) /* Specified page was invalid for op.    */
373#define GNTST_bad_copy_arg    (-10) /* copy arguments cross page boundary */
374
375#define GNTTABOP_error_msgs {                   \
376    "okay",                                     \
377    "undefined error",                          \
378    "unrecognised domain id",                   \
379    "invalid grant reference",                  \
380    "invalid mapping handle",                   \
381    "invalid virtual address",                  \
382    "invalid device address",                   \
383    "no spare translation slot in the I/O MMU", \
384    "permission denied",                        \
385    "bad page",                                 \
386    "copy arguments cross page boundary"        \
387}
388
389#endif /* __XEN_PUBLIC_GRANT_TABLE_H__ */
390
391/*
392 * Local variables:
393 * mode: C
394 * c-set-style: "BSD"
395 * c-basic-offset: 4
396 * tab-width: 4
397 * indent-tabs-mode: nil
398 * End:
399 */
400