Line data Source code
1 0 : /* SPDX-License-Identifier: MIT */
2 :
3 : /******************************************************************************
4 : * grant_table.h
5 : *
6 : * Interface for granting foreign access to page frames, and receiving
7 : * page-ownership transfers.
8 : *
9 : * Permission is hereby granted, free of charge, to any person obtaining a copy
10 : * of this software and associated documentation files (the "Software"), to
11 : * deal in the Software without restriction, including without limitation the
12 : * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
13 : * sell copies of the Software, and to permit persons to whom the Software is
14 : * furnished to do so, subject to the following conditions:
15 : *
16 : * The above copyright notice and this permission notice shall be included in
17 : * all copies or substantial portions of the Software.
18 : *
19 : * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
20 : * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
21 : * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
22 : * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
23 : * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
24 : * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
25 : * DEALINGS IN THE SOFTWARE.
26 : *
27 : * Copyright (c) 2004, K A Fraser
28 : */
29 :
30 : #ifndef __XEN_PUBLIC_GRANT_TABLE_H__
31 : #define __XEN_PUBLIC_GRANT_TABLE_H__
32 :
33 : #include "xen.h"
34 :
35 : /*
36 : * `incontents 150 gnttab Grant Tables
37 : *
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.
41 : *
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
48 : * granter's memory.
49 : *
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.
56 : */
57 :
58 : /***********************************
59 : * GRANT TABLE REPRESENTATION
60 : */
61 :
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
66 : *
67 : * NB. WMB is a no-op on current-generation x86 processors. However, a
68 : * compiler barrier will still be required.
69 : *
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.
78 : *
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.
85 : *
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!).
90 : *
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
101 : * ent->flags).
102 : *
103 : * Invalidating a committed GTF_accept_transfer entry:
104 : * 1. Wait for (ent->flags & GTF_transfer_completed).
105 : *
106 : * Changing a GTF_permit_access from writable to read-only:
107 : * Use SMP-safe CMPXCHG to set GTF_readonly, while checking !GTF_writing.
108 : *
109 : * Changing a GTF_permit_access from read-only to writable:
110 : * Use SMP-safe bit-setting instruction.
111 : */
112 :
113 : /*
114 : * Reference to a grant entry in a specified domain's grant table.
115 : */
116 0 : typedef uint32_t grant_ref_t;
117 :
118 : /*
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.
123 : */
124 :
125 : /*
126 : * Version 1 of the grant table entry structure is maintained purely
127 : * for backwards compatibility. New guests should use version 2.
128 : */
129 : #if CONFIG_XEN_INTERFACE_VERSION < 0x0003020a
130 0 : #define grant_entry_v1 grant_entry
131 0 : #define grant_entry_v1_t grant_entry_t
132 : #endif
133 0 : struct grant_entry_v1 {
134 : /* GTF_xxx: various type and flag information. [XEN,GST] */
135 0 : uint16_t flags;
136 : /* The domain being granted foreign privileges. [GST] */
137 0 : domid_t domid;
138 : /*
139 : * GTF_permit_access: GFN that @domid is allowed to map and access. [GST]
140 : * GTF_accept_transfer: GFN that @domid is allowed to transfer into. [GST]
141 : * GTF_transfer_completed: MFN whose ownership transferred by @domid
142 : * (non-translated guests only). [XEN]
143 : */
144 0 : uint32_t frame;
145 : };
146 0 : typedef struct grant_entry_v1 grant_entry_v1_t;
147 :
148 : /* The first few grant table entries will be preserved across grant table
149 : * version changes and may be pre-populated at domain creation by tools.
150 : */
151 0 : #define GNTTAB_NR_RESERVED_ENTRIES 8
152 0 : #define GNTTAB_RESERVED_CONSOLE 0
153 0 : #define GNTTAB_RESERVED_XENSTORE 1
154 :
155 : /*
156 : * Type of grant entry.
157 : * GTF_invalid: This grant entry grants no privileges.
158 : * GTF_permit_access: Allow @domid to map/access @frame.
159 : * GTF_accept_transfer: Allow @domid to transfer ownership of one page frame
160 : * to this guest. Xen writes the page number to @frame.
161 : * GTF_transitive: Allow @domid to transitively access a subrange of
162 : * @trans_grant in @trans_domid. No mappings are allowed.
163 : */
164 0 : #define GTF_invalid (0U << 0)
165 0 : #define GTF_permit_access (1U << 0)
166 0 : #define GTF_accept_transfer (2U << 0)
167 0 : #define GTF_transitive (3U << 0)
168 0 : #define GTF_type_mask (3U << 0)
169 :
170 : /*
171 : * Subflags for GTF_permit_access and GTF_transitive.
172 : * GTF_readonly: Restrict @domid to read-only mappings and accesses. [GST]
173 : * GTF_reading: Grant entry is currently mapped for reading by @domid. [XEN]
174 : * GTF_writing: Grant entry is currently mapped for writing by @domid. [XEN]
175 : * Further subflags for GTF_permit_access only.
176 : * GTF_PAT, GTF_PWT, GTF_PCD: (x86) cache attribute flags to be used for
177 : * mappings of the grant [GST]
178 : * GTF_sub_page: Grant access to only a subrange of the page. @domid
179 : * will only be allowed to copy from the grant, and not
180 : * map it. [GST]
181 : */
182 : #define _GTF_readonly (2)
183 0 : #define GTF_readonly (1U << _GTF_readonly)
184 : #define _GTF_reading (3)
185 0 : #define GTF_reading (1U << _GTF_reading)
186 : #define _GTF_writing (4)
187 0 : #define GTF_writing (1U << _GTF_writing)
188 : #define _GTF_PWT (5)
189 0 : #define GTF_PWT (1U << _GTF_PWT)
190 : #define _GTF_PCD (6)
191 0 : #define GTF_PCD (1U << _GTF_PCD)
192 : #define _GTF_PAT (7)
193 0 : #define GTF_PAT (1U << _GTF_PAT)
194 : #define _GTF_sub_page (8)
195 0 : #define GTF_sub_page (1U << _GTF_sub_page)
196 :
197 : /*
198 : * Subflags for GTF_accept_transfer:
199 : * GTF_transfer_committed: Xen sets this flag to indicate that it is committed
200 : * to transferring ownership of a page frame. When a guest sees this flag
201 : * it must /not/ modify the grant entry until GTF_transfer_completed is
202 : * set by Xen.
203 : * GTF_transfer_completed: It is safe for the guest to spin-wait on this flag
204 : * after reading GTF_transfer_committed. Xen will always write the frame
205 : * address, followed by ORing this flag, in a timely manner.
206 : */
207 : #define _GTF_transfer_committed (2)
208 0 : #define GTF_transfer_committed (1U << _GTF_transfer_committed)
209 : #define _GTF_transfer_completed (3)
210 0 : #define GTF_transfer_completed (1U << _GTF_transfer_completed)
211 :
212 : /***********************************
213 : * GRANT TABLE QUERIES AND USES
214 : */
215 :
216 : /* ` enum neg_errnoval
217 : * ` HYPERVISOR_grant_table_op(enum grant_table_op cmd,
218 : * ` void *args,
219 : * ` unsigned int count)
220 : * `
221 : *
222 : * @args points to an array of a per-command data structure. The array
223 : * has @count members
224 : */
225 :
226 : /* ` enum grant_table_op { // GNTTABOP_* => struct gnttab_* */
227 0 : #define GNTTABOP_map_grant_ref 0
228 0 : #define GNTTABOP_unmap_grant_ref 1
229 0 : #define GNTTABOP_setup_table 2
230 0 : #define GNTTABOP_dump_table 3
231 0 : #define GNTTABOP_transfer 4
232 0 : #define GNTTABOP_copy 5
233 0 : #define GNTTABOP_query_size 6
234 0 : #define GNTTABOP_unmap_and_replace 7
235 : #if CONFIG_XEN_INTERFACE_VERSION >= 0x0003020a
236 : #define GNTTABOP_set_version 8
237 : #define GNTTABOP_get_status_frames 9
238 : #define GNTTABOP_get_version 10
239 : #define GNTTABOP_swap_grant_ref 11
240 : #define GNTTABOP_cache_flush 12
241 : #endif /* CONFIG_XEN_INTERFACE_VERSION */
242 : /* ` } */
243 :
244 : /*
245 : * Handle to track a mapping created via a grant reference.
246 : */
247 0 : typedef uint32_t grant_handle_t;
248 :
249 : /*
250 : * GNTTABOP_map_grant_ref: Map the grant entry (<dom>,<ref>) for access
251 : * by devices and/or host CPUs. If successful, <handle> is a tracking number
252 : * that must be presented later to destroy the mapping(s). On error, <status>
253 : * is a negative status code.
254 : * NOTES:
255 : * 1. If GNTMAP_device_map is specified then <dev_bus_addr> is the address
256 : * via which I/O devices may access the granted frame.
257 : * 2. If GNTMAP_host_map is specified then a mapping will be added at
258 : * either a host virtual address in the current address space, or at
259 : * a PTE at the specified machine address. The type of mapping to
260 : * perform is selected through the GNTMAP_contains_pte flag, and the
261 : * address is specified in <host_addr>.
262 : * 3. Mappings should only be destroyed via GNTTABOP_unmap_grant_ref. If a
263 : * host mapping is destroyed by other means then it is *NOT* guaranteed
264 : * to be accounted to the correct grant reference!
265 : */
266 0 : struct gnttab_map_grant_ref {
267 : /* IN parameters. */
268 0 : uint64_t host_addr;
269 0 : uint32_t flags; /* GNTMAP_* */
270 0 : grant_ref_t ref;
271 0 : domid_t dom;
272 : /* OUT parameters. */
273 0 : int16_t status; /* => enum grant_status */
274 0 : grant_handle_t handle;
275 0 : uint64_t dev_bus_addr;
276 : };
277 0 : typedef struct gnttab_map_grant_ref gnttab_map_grant_ref_t;
278 0 : DEFINE_XEN_GUEST_HANDLE(gnttab_map_grant_ref_t);
279 :
280 : /*
281 : * GNTTABOP_unmap_grant_ref: Destroy one or more grant-reference mappings
282 : * tracked by <handle>. If <host_addr> or <dev_bus_addr> is zero, that
283 : * field is ignored. If non-zero, they must refer to a device/host mapping
284 : * that is tracked by <handle>
285 : * NOTES:
286 : * 1. The call may fail in an undefined manner if either mapping is not
287 : * tracked by <handle>.
288 : * 3. After executing a batch of unmaps, it is guaranteed that no stale
289 : * mappings will remain in the device or host TLBs.
290 : */
291 0 : struct gnttab_unmap_grant_ref {
292 : /* IN parameters. */
293 0 : uint64_t host_addr;
294 0 : uint64_t dev_bus_addr;
295 0 : grant_handle_t handle;
296 : /* OUT parameters. */
297 0 : int16_t status; /* => enum grant_status */
298 : };
299 0 : typedef struct gnttab_unmap_grant_ref gnttab_unmap_grant_ref_t;
300 0 : DEFINE_XEN_GUEST_HANDLE(gnttab_unmap_grant_ref_t);
301 :
302 : /*
303 : * GNTTABOP_setup_table: Set up a grant table for <dom> comprising at least
304 : * <nr_frames> pages. The frame addresses are written to the <frame_list>.
305 : * Only <nr_frames> addresses are written, even if the table is larger.
306 : * NOTES:
307 : * 1. <dom> may be specified as DOMID_SELF.
308 : * 2. Only a sufficiently-privileged domain may specify <dom> != DOMID_SELF.
309 : * 3. Xen may not support more than a single grant-table page per domain.
310 : */
311 0 : struct gnttab_setup_table {
312 : /* IN parameters. */
313 0 : domid_t dom;
314 0 : uint32_t nr_frames;
315 :
316 : /* OUT parameters. */
317 0 : int16_t status; /* => enum grant_status */
318 : #if CONFIG_XEN_INTERFACE_VERSION < 0x00040300
319 0 : XEN_GUEST_HANDLE(ulong) frame_list;
320 : #else
321 : XEN_GUEST_HANDLE(xen_pfn_t) frame_list;
322 : #endif
323 : };
324 0 : typedef struct gnttab_setup_table gnttab_setup_table_t;
325 0 : DEFINE_XEN_GUEST_HANDLE(gnttab_setup_table_t);
326 :
327 :
328 :
329 : /*
330 : * Bitfield values for gnttab_map_grant_ref.flags.
331 : */
332 : /* Map the grant entry for access by I/O devices. */
333 : #define _GNTMAP_device_map (0)
334 0 : #define GNTMAP_device_map (1<<_GNTMAP_device_map)
335 : /* Map the grant entry for access by host CPUs. */
336 : #define _GNTMAP_host_map (1)
337 0 : #define GNTMAP_host_map (1<<_GNTMAP_host_map)
338 : /* Accesses to the granted frame will be restricted to read-only access. */
339 : #define _GNTMAP_readonly (2)
340 0 : #define GNTMAP_readonly (1<<_GNTMAP_readonly)
341 : /*
342 : * GNTMAP_host_map subflag:
343 : * 0 => The host mapping is usable only by the guest OS.
344 : * 1 => The host mapping is usable by guest OS + current application.
345 : */
346 : #define _GNTMAP_application_map (3)
347 0 : #define GNTMAP_application_map (1<<_GNTMAP_application_map)
348 :
349 : /*
350 : * GNTMAP_contains_pte subflag:
351 : * 0 => This map request contains a host virtual address.
352 : * 1 => This map request contains the machine address of the PTE to update.
353 : */
354 : #define _GNTMAP_contains_pte (4)
355 0 : #define GNTMAP_contains_pte (1<<_GNTMAP_contains_pte)
356 :
357 : /*
358 : * Bits to be placed in guest kernel available PTE bits (architecture
359 : * dependent; only supported when XENFEAT_gnttab_map_avail_bits is set).
360 : */
361 : #define _GNTMAP_guest_avail0 (16)
362 0 : #define GNTMAP_guest_avail_mask ((uint32_t)~0 << _GNTMAP_guest_avail0)
363 :
364 : /*
365 : * Values for error status returns. All errors are -ve.
366 : */
367 : /* ` enum grant_status { */
368 0 : #define GNTST_okay (0) /* Normal return */
369 0 : #define GNTST_general_error (-1) /* General undefined error */
370 0 : #define GNTST_bad_domain (-2) /* Unrecognsed domain id */
371 0 : #define GNTST_bad_gntref (-3) /* Unrecognised or inappropriate gntref */
372 0 : #define GNTST_bad_handle (-4) /* Unrecognised or inappropriate handle */
373 0 : #define GNTST_bad_virt_addr (-5) /* Inappropriate virtual address to map */
374 0 : #define GNTST_bad_dev_addr (-6) /* Inappropriate device address to unmap */
375 0 : #define GNTST_no_device_space (-7) /* Out of space in I/O MMU */
376 0 : #define GNTST_permission_denied (-8) /* Not enough privilege for operation */
377 0 : #define GNTST_bad_page (-9) /* Specified page was invalid for op */
378 0 : #define GNTST_bad_copy_arg (-10) /* copy arguments cross page boundary */
379 0 : #define GNTST_address_too_big (-11) /* transfer page address too large */
380 0 : #define GNTST_eagain (-12) /* Operation not done; try again */
381 : /* ` } */
382 :
383 0 : #define GNTTABOP_error_msgs { \
384 : "okay", \
385 : "undefined error", \
386 : "unrecognised domain id", \
387 : "invalid grant reference", \
388 : "invalid mapping handle", \
389 : "invalid virtual address", \
390 : "invalid device address", \
391 : "no spare translation slot in the I/O MMU", \
392 : "permission denied", \
393 : "bad page", \
394 : "copy arguments cross page boundary", \
395 : "page address size too large", \
396 : "operation not done; try again" \
397 : }
398 :
399 : #endif /* __XEN_PUBLIC_GRANT_TABLE_H__ */
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