1 /******************************************************************************
4 * Interface for granting foreign access to page frames, and receiving
5 * page-ownership transfers.
7 * Copyright (c) 2004, K A Fraser
10 #ifndef __XEN_PUBLIC_GRANT_TABLE_H__
11 #define __XEN_PUBLIC_GRANT_TABLE_H__
14 /***********************************
15 * GRANT TABLE REPRESENTATION
18 /* Some rough guidelines on accessing and updating grant-table entries
19 * in a concurrency-safe manner. For more information, Linux contains a
20 * reference implementation for guest OSes (arch/xen/kernel/grant_table.c).
22 * NB. WMB is a no-op on current-generation x86 processors. However, a
23 * compiler barrier will still be required.
25 * Introducing a valid entry into the grant table:
26 * 1. Write ent->domid.
27 * 2. Write ent->frame:
28 * GTF_permit_access: Frame to which access is permitted.
29 * GTF_accept_transfer: Pseudo-phys frame slot being filled by new
30 * frame, or zero if none.
31 * 3. Write memory barrier (WMB).
32 * 4. Write ent->flags, inc. valid type.
34 * Invalidating an unused GTF_permit_access entry:
35 * 1. flags = ent->flags.
36 * 2. Observe that !(flags & (GTF_reading|GTF_writing)).
37 * 3. Check result of SMP-safe CMPXCHG(&ent->flags, flags, 0).
38 * NB. No need for WMB as reuse of entry is control-dependent on success of
39 * step 3, and all architectures guarantee ordering of ctrl-dep writes.
41 * Invalidating an in-use GTF_permit_access entry:
42 * This cannot be done directly. Request assistance from the domain controller
43 * which can set a timeout on the use of a grant entry and take necessary
44 * action. (NB. This is not yet implemented!).
46 * Invalidating an unused GTF_accept_transfer entry:
47 * 1. flags = ent->flags.
48 * 2. Observe that !(flags & GTF_transfer_committed). [*]
49 * 3. Check result of SMP-safe CMPXCHG(&ent->flags, flags, 0).
50 * NB. No need for WMB as reuse of entry is control-dependent on success of
51 * step 3, and all architectures guarantee ordering of ctrl-dep writes.
52 * [*] If GTF_transfer_committed is set then the grant entry is 'committed'.
53 * The guest must /not/ modify the grant entry until the address of the
54 * transferred frame is written. It is safe for the guest to spin waiting
55 * for this to occur (detect by observing GTF_transfer_completed in
58 * Invalidating a committed GTF_accept_transfer entry:
59 * 1. Wait for (ent->flags & GTF_transfer_completed).
61 * Changing a GTF_permit_access from writable to read-only:
62 * Use SMP-safe CMPXCHG to set GTF_readonly, while checking !GTF_writing.
64 * Changing a GTF_permit_access from read-only to writable:
65 * Use SMP-safe bit-setting instruction.
69 * A grant table comprises a packed array of grant entries in one or more
70 * page frames shared between Xen and a guest.
71 * [XEN]: This field is written by Xen and read by the sharing guest.
72 * [GST]: This field is written by the guest and read by Xen.
75 /* GTF_xxx: various type and flag information. [XEN,GST] */
77 /* The domain being granted foreign privileges. [GST] */
80 * GTF_permit_access: Frame that @domid is allowed to map and access. [GST]
81 * GTF_accept_transfer: Frame whose ownership transferred by @domid. [XEN]
85 typedef struct grant_entry grant_entry_t;
88 * Type of grant entry.
89 * GTF_invalid: This grant entry grants no privileges.
90 * GTF_permit_access: Allow @domid to map/access @frame.
91 * GTF_accept_transfer: Allow @domid to transfer ownership of one page frame
92 * to this guest. Xen writes the page number to @frame.
94 #define GTF_invalid (0U<<0)
95 #define GTF_permit_access (1U<<0)
96 #define GTF_accept_transfer (2U<<0)
97 #define GTF_type_mask (3U<<0)
100 * Subflags for GTF_permit_access.
101 * GTF_readonly: Restrict @domid to read-only mappings and accesses. [GST]
102 * GTF_reading: Grant entry is currently mapped for reading by @domid. [XEN]
103 * GTF_writing: Grant entry is currently mapped for writing by @domid. [XEN]
105 #define _GTF_readonly (2)
106 #define GTF_readonly (1U<<_GTF_readonly)
107 #define _GTF_reading (3)
108 #define GTF_reading (1U<<_GTF_reading)
109 #define _GTF_writing (4)
110 #define GTF_writing (1U<<_GTF_writing)
113 * Subflags for GTF_accept_transfer:
114 * GTF_transfer_committed: Xen sets this flag to indicate that it is committed
115 * to transferring ownership of a page frame. When a guest sees this flag
116 * it must /not/ modify the grant entry until GTF_transfer_completed is
118 * GTF_transfer_completed: It is safe for the guest to spin-wait on this flag
119 * after reading GTF_transfer_committed. Xen will always write the frame
120 * address, followed by ORing this flag, in a timely manner.
122 #define _GTF_transfer_committed (2)
123 #define GTF_transfer_committed (1U<<_GTF_transfer_committed)
124 #define _GTF_transfer_completed (3)
125 #define GTF_transfer_completed (1U<<_GTF_transfer_completed)
128 /***********************************
129 * GRANT TABLE QUERIES AND USES
133 * Reference to a grant entry in a specified domain's grant table.
135 typedef uint32_t grant_ref_t;
138 * Handle to track a mapping created via a grant reference.
140 typedef uint32_t grant_handle_t;
143 * GNTTABOP_map_grant_ref: Map the grant entry (<dom>,<ref>) for access
144 * by devices and/or host CPUs. If successful, <handle> is a tracking number
145 * that must be presented later to destroy the mapping(s). On error, <handle>
146 * is a negative status code.
148 * 1. If GNTMAP_device_map is specified then <dev_bus_addr> is the address
149 * via which I/O devices may access the granted frame.
150 * 2. If GNTMAP_host_map is specified then a mapping will be added at
151 * either a host virtual address in the current address space, or at
152 * a PTE at the specified machine address. The type of mapping to
153 * perform is selected through the GNTMAP_contains_pte flag, and the
154 * address is specified in <host_addr>.
155 * 3. Mappings should only be destroyed via GNTTABOP_unmap_grant_ref. If a
156 * host mapping is destroyed by other means then it is *NOT* guaranteed
157 * to be accounted to the correct grant reference!
159 #define GNTTABOP_map_grant_ref 0
160 struct gnttab_map_grant_ref {
163 uint32_t flags; /* GNTMAP_* */
166 /* OUT parameters. */
167 int16_t status; /* GNTST_* */
168 grant_handle_t handle;
169 uint64_t dev_bus_addr;
171 typedef struct gnttab_map_grant_ref gnttab_map_grant_ref_t;
172 DEFINE_XEN_GUEST_HANDLE(gnttab_map_grant_ref_t);
175 * GNTTABOP_unmap_grant_ref: Destroy one or more grant-reference mappings
176 * tracked by <handle>. If <host_addr> or <dev_bus_addr> is zero, that
177 * field is ignored. If non-zero, they must refer to a device/host mapping
178 * that is tracked by <handle>
180 * 1. The call may fail in an undefined manner if either mapping is not
181 * tracked by <handle>.
182 * 3. After executing a batch of unmaps, it is guaranteed that no stale
183 * mappings will remain in the device or host TLBs.
185 #define GNTTABOP_unmap_grant_ref 1
186 struct gnttab_unmap_grant_ref {
189 uint64_t dev_bus_addr;
190 grant_handle_t handle;
191 /* OUT parameters. */
192 int16_t status; /* GNTST_* */
194 typedef struct gnttab_unmap_grant_ref gnttab_unmap_grant_ref_t;
195 DEFINE_XEN_GUEST_HANDLE(gnttab_unmap_grant_ref_t);
198 * GNTTABOP_setup_table: Set up a grant table for <dom> comprising at least
199 * <nr_frames> pages. The frame addresses are written to the <frame_list>.
200 * Only <nr_frames> addresses are written, even if the table is larger.
202 * 1. <dom> may be specified as DOMID_SELF.
203 * 2. Only a sufficiently-privileged domain may specify <dom> != DOMID_SELF.
204 * 3. Xen may not support more than a single grant-table page per domain.
206 #define GNTTABOP_setup_table 2
207 struct gnttab_setup_table {
211 /* OUT parameters. */
212 int16_t status; /* GNTST_* */
213 XEN_GUEST_HANDLE(ulong) frame_list;
215 typedef struct gnttab_setup_table gnttab_setup_table_t;
216 DEFINE_XEN_GUEST_HANDLE(gnttab_setup_table_t);
219 * GNTTABOP_dump_table: Dump the contents of the grant table to the
220 * xen console. Debugging use only.
222 #define GNTTABOP_dump_table 3
223 struct gnttab_dump_table {
226 /* OUT parameters. */
227 int16_t status; /* GNTST_* */
229 typedef struct gnttab_dump_table gnttab_dump_table_t;
230 DEFINE_XEN_GUEST_HANDLE(gnttab_dump_table_t);
233 * GNTTABOP_transfer_grant_ref: Transfer <frame> to a foreign domain. The
234 * foreign domain has previously registered its interest in the transfer via
237 * Note that, even if the transfer fails, the specified page no longer belongs
238 * to the calling domain *unless* the error is GNTST_bad_page.
240 #define GNTTABOP_transfer 4
241 struct gnttab_transfer {
246 /* OUT parameters. */
249 typedef struct gnttab_transfer gnttab_transfer_t;
250 DEFINE_XEN_GUEST_HANDLE(gnttab_transfer_t);
254 * GNTTABOP_copy: Hypervisor based copy
255 * source and destinations can be eithers MFNs or, for foreign domains,
256 * grant references. the foreign domain has to grant read/write access
257 * in its grant table.
259 * The flags specify what type source and destinations are (either MFN
260 * or grant reference).
262 * Note that this can also be used to copy data between two domains
263 * via a third party if the source and destination domains had previously
264 * grant appropriate access to their pages to the third party.
266 * source_offset specifies an offset in the source frame, dest_offset
267 * the offset in the target frame and len specifies the number of
268 * bytes to be copied.
271 #define _GNTCOPY_source_gref (0)
272 #define GNTCOPY_source_gref (1<<_GNTCOPY_source_gref)
273 #define _GNTCOPY_dest_gref (1)
274 #define GNTCOPY_dest_gref (1<<_GNTCOPY_dest_gref)
276 #define GNTTABOP_copy 5
277 typedef struct gnttab_copy {
288 uint16_t flags; /* GNTCOPY_* */
289 /* OUT parameters. */
292 DEFINE_XEN_GUEST_HANDLE(gnttab_copy_t);
296 * Bitfield values for update_pin_status.flags.
298 /* Map the grant entry for access by I/O devices. */
299 #define _GNTMAP_device_map (0)
300 #define GNTMAP_device_map (1<<_GNTMAP_device_map)
301 /* Map the grant entry for access by host CPUs. */
302 #define _GNTMAP_host_map (1)
303 #define GNTMAP_host_map (1<<_GNTMAP_host_map)
304 /* Accesses to the granted frame will be restricted to read-only access. */
305 #define _GNTMAP_readonly (2)
306 #define GNTMAP_readonly (1<<_GNTMAP_readonly)
308 * GNTMAP_host_map subflag:
309 * 0 => The host mapping is usable only by the guest OS.
310 * 1 => The host mapping is usable by guest OS + current application.
312 #define _GNTMAP_application_map (3)
313 #define GNTMAP_application_map (1<<_GNTMAP_application_map)
316 * GNTMAP_contains_pte subflag:
317 * 0 => This map request contains a host virtual address.
318 * 1 => This map request contains the machine addess of the PTE to update.
320 #define _GNTMAP_contains_pte (4)
321 #define GNTMAP_contains_pte (1<<_GNTMAP_contains_pte)
324 * Values for error status returns. All errors are -ve.
326 #define GNTST_okay (0) /* Normal return. */
327 #define GNTST_general_error (-1) /* General undefined error. */
328 #define GNTST_bad_domain (-2) /* Unrecognsed domain id. */
329 #define GNTST_bad_gntref (-3) /* Unrecognised or inappropriate gntref. */
330 #define GNTST_bad_handle (-4) /* Unrecognised or inappropriate handle. */
331 #define GNTST_bad_virt_addr (-5) /* Inappropriate virtual address to map. */
332 #define GNTST_bad_dev_addr (-6) /* Inappropriate device address to unmap.*/
333 #define GNTST_no_device_space (-7) /* Out of space in I/O MMU. */
334 #define GNTST_permission_denied (-8) /* Not enough privilege for operation. */
335 #define GNTST_bad_page (-9) /* Specified page was invalid for op. */
336 #define GNTST_bad_copy_arg (-10) /* copy arguments cross page boundary */
338 #define GNTTABOP_error_msgs { \
341 "unrecognised domain id", \
342 "invalid grant reference", \
343 "invalid mapping handle", \
344 "invalid virtual address", \
345 "invalid device address", \
346 "no spare translation slot in the I/O MMU", \
347 "permission denied", \
349 "copy arguments cross page boundary" \
352 #endif /* __XEN_PUBLIC_GRANT_TABLE_H__ */
360 * indent-tabs-mode: nil