Zephyr API Documentation  3.6.99
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grant_table.h
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1/* 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 */
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 __XEN_INTERFACE_VERSION__ < 0x0003020a
130#define grant_entry_v1 grant_entry
131#define grant_entry_v1_t grant_entry_t
132#endif
134 /* GTF_xxx: various type and flag information. [XEN,GST] */
136 /* The domain being granted foreign privileges. [GST] */
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 */
145};
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#define GNTTAB_NR_RESERVED_ENTRIES 8
152#define GNTTAB_RESERVED_CONSOLE 0
153#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#define GTF_invalid (0U << 0)
165#define GTF_permit_access (1U << 0)
166#define GTF_accept_transfer (2U << 0)
167#define GTF_transitive (3U << 0)
168#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#define GTF_readonly (1U << _GTF_readonly)
184#define _GTF_reading (3)
185#define GTF_reading (1U << _GTF_reading)
186#define _GTF_writing (4)
187#define GTF_writing (1U << _GTF_writing)
188#define _GTF_PWT (5)
189#define GTF_PWT (1U << _GTF_PWT)
190#define _GTF_PCD (6)
191#define GTF_PCD (1U << _GTF_PCD)
192#define _GTF_PAT (7)
193#define GTF_PAT (1U << _GTF_PAT)
194#define _GTF_sub_page (8)
195#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#define GTF_transfer_committed (1U << _GTF_transfer_committed)
209#define _GTF_transfer_completed (3)
210#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#define GNTTABOP_map_grant_ref 0
228#define GNTTABOP_unmap_grant_ref 1
229#define GNTTABOP_setup_table 2
230#define GNTTABOP_dump_table 3
231#define GNTTABOP_transfer 4
232#define GNTTABOP_copy 5
233#define GNTTABOP_query_size 6
234#define GNTTABOP_unmap_and_replace 7
235#if __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 /* __XEN_INTERFACE_VERSION__ */
242/* ` } */
243
244/*
245 * Handle to track a mapping created via a grant reference.
246 */
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 */
267 /* IN parameters. */
269 uint32_t flags; /* GNTMAP_* */
272 /* OUT parameters. */
273 int16_t status; /* => enum grant_status */
276};
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 */
292 /* IN parameters. */
296 /* OUT parameters. */
297 int16_t status; /* => enum grant_status */
298};
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 */
312 /* IN parameters. */
315
316 /* OUT parameters. */
317 int16_t status; /* => enum grant_status */
318#if __XEN_INTERFACE_VERSION__ < 0x00040300
319 XEN_GUEST_HANDLE(ulong) frame_list;
320#else
321 XEN_GUEST_HANDLE(xen_pfn_t) frame_list;
322#endif
323};
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#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#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#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#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 addess of the PTE to update.
353 */
354#define _GNTMAP_contains_pte (4)
355#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#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#define GNTST_okay (0) /* Normal return */
369#define GNTST_general_error (-1) /* General undefined error */
370#define GNTST_bad_domain (-2) /* Unrecognsed domain id */
371#define GNTST_bad_gntref (-3) /* Unrecognised or inappropriate gntref */
372#define GNTST_bad_handle (-4) /* Unrecognised or inappropriate handle */
373#define GNTST_bad_virt_addr (-5) /* Inappropriate virtual address to map */
374#define GNTST_bad_dev_addr (-6) /* Inappropriate device address to unmap */
375#define GNTST_no_device_space (-7) /* Out of space in I/O MMU */
376#define GNTST_permission_denied (-8) /* Not enough privilege for operation */
377#define GNTST_bad_page (-9) /* Specified page was invalid for op */
378#define GNTST_bad_copy_arg (-10) /* copy arguments cross page boundary */
379#define GNTST_address_too_big (-11) /* transfer page address too large */
380#define GNTST_eagain (-12) /* Operation not done; try agains */
381/* ` } */
382
383#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__ */
uint64_t xen_pfn_t
Definition: arch-arm.h:204
#define XEN_GUEST_HANDLE(name)
Definition: arch-arm.h:194
#define DEFINE_XEN_GUEST_HANDLE(name)
Definition: arch-arm.h:192
uint32_t grant_handle_t
Definition: grant_table.h:247
#define grant_entry_v1_t
Definition: grant_table.h:131
#define grant_entry_v1
Definition: grant_table.h:130
uint32_t grant_ref_t
Definition: grant_table.h:116
__UINT32_TYPE__ uint32_t
Definition: stdint.h:90
__UINT64_TYPE__ uint64_t
Definition: stdint.h:91
__UINT16_TYPE__ uint16_t
Definition: stdint.h:89
__INT16_TYPE__ int16_t
Definition: stdint.h:73
Definition: grant_table.h:266
uint32_t flags
Definition: grant_table.h:269
domid_t dom
Definition: grant_table.h:271
uint64_t host_addr
Definition: grant_table.h:268
grant_handle_t handle
Definition: grant_table.h:274
int16_t status
Definition: grant_table.h:273
uint64_t dev_bus_addr
Definition: grant_table.h:275
grant_ref_t ref
Definition: grant_table.h:270
Definition: grant_table.h:311
uint32_t nr_frames
Definition: grant_table.h:314
domid_t dom
Definition: grant_table.h:313
XEN_GUEST_HANDLE(ulong) frame_list
int16_t status
Definition: grant_table.h:317
Definition: grant_table.h:291
grant_handle_t handle
Definition: grant_table.h:295
uint64_t host_addr
Definition: grant_table.h:293
uint64_t dev_bus_addr
Definition: grant_table.h:294
int16_t status
Definition: grant_table.h:297
domid_t domid
Definition: grant_table.h:137
uint32_t frame
Definition: grant_table.h:144
uint16_t flags
Definition: grant_table.h:135
uint16_t domid_t
Definition: xen.h:217