1 /* SPDX-License-Identifier: MIT */ 2 /****************************************************************************** 3 * grant_table.h 4 * 5 * Interface for granting foreign access to page frames, and receiving 6 * page-ownership transfers. 7 * 8 * Copyright (c) 2004, K A Fraser 9 */ 10 11 #ifndef __XEN_PUBLIC_GRANT_TABLE_H__ 12 #define __XEN_PUBLIC_GRANT_TABLE_H__ 13 14 #include <xen/interface/xen.h> 15 16 /*********************************** 17 * GRANT TABLE REPRESENTATION 18 */ 19 20 /* Some rough guidelines on accessing and updating grant-table entries 21 * in a concurrency-safe manner. For more information, Linux contains a 22 * reference implementation for guest OSes (arch/xen/kernel/grant_table.c). 23 * 24 * NB. WMB is a no-op on current-generation x86 processors. However, a 25 * compiler barrier will still be required. 26 * 27 * Introducing a valid entry into the grant table: 28 * 1. Write ent->domid. 29 * 2. Write ent->frame: 30 * GTF_permit_access: Frame to which access is permitted. 31 * GTF_accept_transfer: Pseudo-phys frame slot being filled by new 32 * frame, or zero if none. 33 * 3. Write memory barrier (WMB). 34 * 4. Write ent->flags, inc. valid type. 35 * 36 * Invalidating an unused GTF_permit_access entry: 37 * 1. flags = ent->flags. 38 * 2. Observe that !(flags & (GTF_reading|GTF_writing)). 39 * 3. Check result of SMP-safe CMPXCHG(&ent->flags, flags, 0). 40 * NB. No need for WMB as reuse of entry is control-dependent on success of 41 * step 3, and all architectures guarantee ordering of ctrl-dep writes. 42 * 43 * Invalidating an in-use GTF_permit_access entry: 44 * This cannot be done directly. Request assistance from the domain controller 45 * which can set a timeout on the use of a grant entry and take necessary 46 * action. (NB. This is not yet implemented!). 47 * 48 * Invalidating an unused GTF_accept_transfer entry: 49 * 1. flags = ent->flags. 50 * 2. Observe that !(flags & GTF_transfer_committed). [*] 51 * 3. Check result of SMP-safe CMPXCHG(&ent->flags, flags, 0). 52 * NB. No need for WMB as reuse of entry is control-dependent on success of 53 * step 3, and all architectures guarantee ordering of ctrl-dep writes. 54 * [*] If GTF_transfer_committed is set then the grant entry is 'committed'. 55 * The guest must /not/ modify the grant entry until the address of the 56 * transferred frame is written. It is safe for the guest to spin waiting 57 * for this to occur (detect by observing GTF_transfer_completed in 58 * ent->flags). 59 * 60 * Invalidating a committed GTF_accept_transfer entry: 61 * 1. Wait for (ent->flags & GTF_transfer_completed). 62 * 63 * Changing a GTF_permit_access from writable to read-only: 64 * Use SMP-safe CMPXCHG to set GTF_readonly, while checking !GTF_writing. 65 * 66 * Changing a GTF_permit_access from read-only to writable: 67 * Use SMP-safe bit-setting instruction. 68 */ 69 70 /* 71 * Reference to a grant entry in a specified domain's grant table. 72 */ 73 typedef uint32_t grant_ref_t; 74 75 /* 76 * A grant table comprises a packed array of grant entries in one or more 77 * page frames shared between Xen and a guest. 78 * [XEN]: This field is written by Xen and read by the sharing guest. 79 * [GST]: This field is written by the guest and read by Xen. 80 */ 81 82 /* 83 * Version 1 of the grant table entry structure is maintained purely 84 * for backwards compatibility. New guests should use version 2. 85 */ 86 struct grant_entry_v1 { 87 /* GTF_xxx: various type and flag information. [XEN,GST] */ 88 uint16_t flags; 89 /* The domain being granted foreign privileges. [GST] */ 90 domid_t domid; 91 /* 92 * GTF_permit_access: Frame that @domid is allowed to map and access. [GST] 93 * GTF_accept_transfer: Frame whose ownership transferred by @domid. [XEN] 94 */ 95 uint32_t frame; 96 }; 97 98 /* 99 * Type of grant entry. 100 * GTF_invalid: This grant entry grants no privileges. 101 * GTF_permit_access: Allow @domid to map/access @frame. 102 * GTF_accept_transfer: Allow @domid to transfer ownership of one page frame 103 * to this guest. Xen writes the page number to @frame. 104 * GTF_transitive: Allow @domid to transitively access a subrange of 105 * @trans_grant in @trans_domid. No mappings are allowed. 106 */ 107 #define GTF_invalid (0U<<0) 108 #define GTF_permit_access (1U<<0) 109 #define GTF_accept_transfer (2U<<0) 110 #define GTF_transitive (3U<<0) 111 #define GTF_type_mask (3U<<0) 112 113 /* 114 * Subflags for GTF_permit_access. 115 * GTF_readonly: Restrict @domid to read-only mappings and accesses. [GST] 116 * GTF_reading: Grant entry is currently mapped for reading by @domid. [XEN] 117 * GTF_writing: Grant entry is currently mapped for writing by @domid. [XEN] 118 * GTF_sub_page: Grant access to only a subrange of the page. @domid 119 * will only be allowed to copy from the grant, and not 120 * map it. [GST] 121 */ 122 #define _GTF_readonly (2) 123 #define GTF_readonly (1U<<_GTF_readonly) 124 #define _GTF_reading (3) 125 #define GTF_reading (1U<<_GTF_reading) 126 #define _GTF_writing (4) 127 #define GTF_writing (1U<<_GTF_writing) 128 #define _GTF_sub_page (8) 129 #define GTF_sub_page (1U<<_GTF_sub_page) 130 131 /* 132 * Subflags for GTF_accept_transfer: 133 * GTF_transfer_committed: Xen sets this flag to indicate that it is committed 134 * to transferring ownership of a page frame. When a guest sees this flag 135 * it must /not/ modify the grant entry until GTF_transfer_completed is 136 * set by Xen. 137 * GTF_transfer_completed: It is safe for the guest to spin-wait on this flag 138 * after reading GTF_transfer_committed. Xen will always write the frame 139 * address, followed by ORing this flag, in a timely manner. 140 */ 141 #define _GTF_transfer_committed (2) 142 #define GTF_transfer_committed (1U<<_GTF_transfer_committed) 143 #define _GTF_transfer_completed (3) 144 #define GTF_transfer_completed (1U<<_GTF_transfer_completed) 145 146 /* 147 * Version 2 grant table entries. These fulfil the same role as 148 * version 1 entries, but can represent more complicated operations. 149 * Any given domain will have either a version 1 or a version 2 table, 150 * and every entry in the table will be the same version. 151 * 152 * The interface by which domains use grant references does not depend 153 * on the grant table version in use by the other domain. 154 */ 155 156 /* 157 * Version 1 and version 2 grant entries share a common prefix. The 158 * fields of the prefix are documented as part of struct 159 * grant_entry_v1. 160 */ 161 struct grant_entry_header { 162 uint16_t flags; 163 domid_t domid; 164 }; 165 166 /* 167 * Version 2 of the grant entry structure, here is a union because three 168 * different types are suppotted: full_page, sub_page and transitive. 169 */ 170 union grant_entry_v2 { 171 struct grant_entry_header hdr; 172 173 /* 174 * This member is used for V1-style full page grants, where either: 175 * 176 * -- hdr.type is GTF_accept_transfer, or 177 * -- hdr.type is GTF_permit_access and GTF_sub_page is not set. 178 * 179 * In that case, the frame field has the same semantics as the 180 * field of the same name in the V1 entry structure. 181 */ 182 struct { 183 struct grant_entry_header hdr; 184 uint32_t pad0; 185 uint64_t frame; 186 } full_page; 187 188 /* 189 * If the grant type is GTF_grant_access and GTF_sub_page is set, 190 * @domid is allowed to access bytes [@page_off,@page_off+@length) 191 * in frame @frame. 192 */ 193 struct { 194 struct grant_entry_header hdr; 195 uint16_t page_off; 196 uint16_t length; 197 uint64_t frame; 198 } sub_page; 199 200 /* 201 * If the grant is GTF_transitive, @domid is allowed to use the 202 * grant @gref in domain @trans_domid, as if it was the local 203 * domain. Obviously, the transitive access must be compatible 204 * with the original grant. 205 */ 206 struct { 207 struct grant_entry_header hdr; 208 domid_t trans_domid; 209 uint16_t pad0; 210 grant_ref_t gref; 211 } transitive; 212 213 uint32_t __spacer[4]; /* Pad to a power of two */ 214 }; 215 216 typedef uint16_t grant_status_t; 217 218 /*********************************** 219 * GRANT TABLE QUERIES AND USES 220 */ 221 222 /* 223 * Handle to track a mapping created via a grant reference. 224 */ 225 typedef uint32_t grant_handle_t; 226 227 /* 228 * GNTTABOP_map_grant_ref: Map the grant entry (<dom>,<ref>) for access 229 * by devices and/or host CPUs. If successful, <handle> is a tracking number 230 * that must be presented later to destroy the mapping(s). On error, <handle> 231 * is a negative status code. 232 * NOTES: 233 * 1. If GNTMAP_device_map is specified then <dev_bus_addr> is the address 234 * via which I/O devices may access the granted frame. 235 * 2. If GNTMAP_host_map is specified then a mapping will be added at 236 * either a host virtual address in the current address space, or at 237 * a PTE at the specified machine address. The type of mapping to 238 * perform is selected through the GNTMAP_contains_pte flag, and the 239 * address is specified in <host_addr>. 240 * 3. Mappings should only be destroyed via GNTTABOP_unmap_grant_ref. If a 241 * host mapping is destroyed by other means then it is *NOT* guaranteed 242 * to be accounted to the correct grant reference! 243 */ 244 #define GNTTABOP_map_grant_ref 0 245 struct gnttab_map_grant_ref { 246 /* IN parameters. */ 247 uint64_t host_addr; 248 uint32_t flags; /* GNTMAP_* */ 249 grant_ref_t ref; 250 domid_t dom; 251 /* OUT parameters. */ 252 int16_t status; /* GNTST_* */ 253 grant_handle_t handle; 254 uint64_t dev_bus_addr; 255 }; 256 DEFINE_GUEST_HANDLE_STRUCT(gnttab_map_grant_ref); 257 258 /* 259 * GNTTABOP_unmap_grant_ref: Destroy one or more grant-reference mappings 260 * tracked by <handle>. If <host_addr> or <dev_bus_addr> is zero, that 261 * field is ignored. If non-zero, they must refer to a device/host mapping 262 * that is tracked by <handle> 263 * NOTES: 264 * 1. The call may fail in an undefined manner if either mapping is not 265 * tracked by <handle>. 266 * 3. After executing a batch of unmaps, it is guaranteed that no stale 267 * mappings will remain in the device or host TLBs. 268 */ 269 #define GNTTABOP_unmap_grant_ref 1 270 struct gnttab_unmap_grant_ref { 271 /* IN parameters. */ 272 uint64_t host_addr; 273 uint64_t dev_bus_addr; 274 grant_handle_t handle; 275 /* OUT parameters. */ 276 int16_t status; /* GNTST_* */ 277 }; 278 DEFINE_GUEST_HANDLE_STRUCT(gnttab_unmap_grant_ref); 279 280 /* 281 * GNTTABOP_setup_table: Set up a grant table for <dom> comprising at least 282 * <nr_frames> pages. The frame addresses are written to the <frame_list>. 283 * Only <nr_frames> addresses are written, even if the table is larger. 284 * NOTES: 285 * 1. <dom> may be specified as DOMID_SELF. 286 * 2. Only a sufficiently-privileged domain may specify <dom> != DOMID_SELF. 287 * 3. Xen may not support more than a single grant-table page per domain. 288 */ 289 #define GNTTABOP_setup_table 2 290 struct gnttab_setup_table { 291 /* IN parameters. */ 292 domid_t dom; 293 uint32_t nr_frames; 294 /* OUT parameters. */ 295 int16_t status; /* GNTST_* */ 296 GUEST_HANDLE(xen_pfn_t) frame_list; 297 }; 298 DEFINE_GUEST_HANDLE_STRUCT(gnttab_setup_table); 299 300 /* 301 * GNTTABOP_dump_table: Dump the contents of the grant table to the 302 * xen console. Debugging use only. 303 */ 304 #define GNTTABOP_dump_table 3 305 struct gnttab_dump_table { 306 /* IN parameters. */ 307 domid_t dom; 308 /* OUT parameters. */ 309 int16_t status; /* GNTST_* */ 310 }; 311 DEFINE_GUEST_HANDLE_STRUCT(gnttab_dump_table); 312 313 /* 314 * GNTTABOP_transfer_grant_ref: Transfer <frame> to a foreign domain. The 315 * foreign domain has previously registered its interest in the transfer via 316 * <domid, ref>. 317 * 318 * Note that, even if the transfer fails, the specified page no longer belongs 319 * to the calling domain *unless* the error is GNTST_bad_page. 320 */ 321 #define GNTTABOP_transfer 4 322 struct gnttab_transfer { 323 /* IN parameters. */ 324 xen_pfn_t mfn; 325 domid_t domid; 326 grant_ref_t ref; 327 /* OUT parameters. */ 328 int16_t status; 329 }; 330 DEFINE_GUEST_HANDLE_STRUCT(gnttab_transfer); 331 332 /* 333 * GNTTABOP_copy: Hypervisor based copy 334 * source and destinations can be eithers MFNs or, for foreign domains, 335 * grant references. the foreign domain has to grant read/write access 336 * in its grant table. 337 * 338 * The flags specify what type source and destinations are (either MFN 339 * or grant reference). 340 * 341 * Note that this can also be used to copy data between two domains 342 * via a third party if the source and destination domains had previously 343 * grant appropriate access to their pages to the third party. 344 * 345 * source_offset specifies an offset in the source frame, dest_offset 346 * the offset in the target frame and len specifies the number of 347 * bytes to be copied. 348 */ 349 350 #define _GNTCOPY_source_gref (0) 351 #define GNTCOPY_source_gref (1<<_GNTCOPY_source_gref) 352 #define _GNTCOPY_dest_gref (1) 353 #define GNTCOPY_dest_gref (1<<_GNTCOPY_dest_gref) 354 355 #define GNTTABOP_copy 5 356 struct gnttab_copy { 357 /* IN parameters. */ 358 struct { 359 union { 360 grant_ref_t ref; 361 xen_pfn_t gmfn; 362 } u; 363 domid_t domid; 364 uint16_t offset; 365 } source, dest; 366 uint16_t len; 367 uint16_t flags; /* GNTCOPY_* */ 368 /* OUT parameters. */ 369 int16_t status; 370 }; 371 DEFINE_GUEST_HANDLE_STRUCT(gnttab_copy); 372 373 /* 374 * GNTTABOP_query_size: Query the current and maximum sizes of the shared 375 * grant table. 376 * NOTES: 377 * 1. <dom> may be specified as DOMID_SELF. 378 * 2. Only a sufficiently-privileged domain may specify <dom> != DOMID_SELF. 379 */ 380 #define GNTTABOP_query_size 6 381 struct gnttab_query_size { 382 /* IN parameters. */ 383 domid_t dom; 384 /* OUT parameters. */ 385 uint32_t nr_frames; 386 uint32_t max_nr_frames; 387 int16_t status; /* GNTST_* */ 388 }; 389 DEFINE_GUEST_HANDLE_STRUCT(gnttab_query_size); 390 391 /* 392 * GNTTABOP_unmap_and_replace: Destroy one or more grant-reference mappings 393 * tracked by <handle> but atomically replace the page table entry with one 394 * pointing to the machine address under <new_addr>. <new_addr> will be 395 * redirected to the null entry. 396 * NOTES: 397 * 1. The call may fail in an undefined manner if either mapping is not 398 * tracked by <handle>. 399 * 2. After executing a batch of unmaps, it is guaranteed that no stale 400 * mappings will remain in the device or host TLBs. 401 */ 402 #define GNTTABOP_unmap_and_replace 7 403 struct gnttab_unmap_and_replace { 404 /* IN parameters. */ 405 uint64_t host_addr; 406 uint64_t new_addr; 407 grant_handle_t handle; 408 /* OUT parameters. */ 409 int16_t status; /* GNTST_* */ 410 }; 411 DEFINE_GUEST_HANDLE_STRUCT(gnttab_unmap_and_replace); 412 413 /* 414 * GNTTABOP_set_version: Request a particular version of the grant 415 * table shared table structure. This operation can only be performed 416 * once in any given domain. It must be performed before any grants 417 * are activated; otherwise, the domain will be stuck with version 1. 418 * The only defined versions are 1 and 2. 419 */ 420 #define GNTTABOP_set_version 8 421 struct gnttab_set_version { 422 /* IN parameters */ 423 uint32_t version; 424 }; 425 DEFINE_GUEST_HANDLE_STRUCT(gnttab_set_version); 426 427 /* 428 * GNTTABOP_get_status_frames: Get the list of frames used to store grant 429 * status for <dom>. In grant format version 2, the status is separated 430 * from the other shared grant fields to allow more efficient synchronization 431 * using barriers instead of atomic cmpexch operations. 432 * <nr_frames> specify the size of vector <frame_list>. 433 * The frame addresses are returned in the <frame_list>. 434 * Only <nr_frames> addresses are returned, even if the table is larger. 435 * NOTES: 436 * 1. <dom> may be specified as DOMID_SELF. 437 * 2. Only a sufficiently-privileged domain may specify <dom> != DOMID_SELF. 438 */ 439 #define GNTTABOP_get_status_frames 9 440 struct gnttab_get_status_frames { 441 /* IN parameters. */ 442 uint32_t nr_frames; 443 domid_t dom; 444 /* OUT parameters. */ 445 int16_t status; /* GNTST_* */ 446 GUEST_HANDLE(uint64_t) frame_list; 447 }; 448 DEFINE_GUEST_HANDLE_STRUCT(gnttab_get_status_frames); 449 450 /* 451 * GNTTABOP_get_version: Get the grant table version which is in 452 * effect for domain <dom>. 453 */ 454 #define GNTTABOP_get_version 10 455 struct gnttab_get_version { 456 /* IN parameters */ 457 domid_t dom; 458 uint16_t pad; 459 /* OUT parameters */ 460 uint32_t version; 461 }; 462 DEFINE_GUEST_HANDLE_STRUCT(gnttab_get_version); 463 464 /* 465 * Issue one or more cache maintenance operations on a portion of a 466 * page granted to the calling domain by a foreign domain. 467 */ 468 #define GNTTABOP_cache_flush 12 469 struct gnttab_cache_flush { 470 union { 471 uint64_t dev_bus_addr; 472 grant_ref_t ref; 473 } a; 474 uint16_t offset; /* offset from start of grant */ 475 uint16_t length; /* size within the grant */ 476 #define GNTTAB_CACHE_CLEAN (1<<0) 477 #define GNTTAB_CACHE_INVAL (1<<1) 478 #define GNTTAB_CACHE_SOURCE_GREF (1<<31) 479 uint32_t op; 480 }; 481 DEFINE_GUEST_HANDLE_STRUCT(gnttab_cache_flush); 482 483 /* 484 * Bitfield values for update_pin_status.flags. 485 */ 486 /* Map the grant entry for access by I/O devices. */ 487 #define _GNTMAP_device_map (0) 488 #define GNTMAP_device_map (1<<_GNTMAP_device_map) 489 /* Map the grant entry for access by host CPUs. */ 490 #define _GNTMAP_host_map (1) 491 #define GNTMAP_host_map (1<<_GNTMAP_host_map) 492 /* Accesses to the granted frame will be restricted to read-only access. */ 493 #define _GNTMAP_readonly (2) 494 #define GNTMAP_readonly (1<<_GNTMAP_readonly) 495 /* 496 * GNTMAP_host_map subflag: 497 * 0 => The host mapping is usable only by the guest OS. 498 * 1 => The host mapping is usable by guest OS + current application. 499 */ 500 #define _GNTMAP_application_map (3) 501 #define GNTMAP_application_map (1<<_GNTMAP_application_map) 502 503 /* 504 * GNTMAP_contains_pte subflag: 505 * 0 => This map request contains a host virtual address. 506 * 1 => This map request contains the machine addess of the PTE to update. 507 */ 508 #define _GNTMAP_contains_pte (4) 509 #define GNTMAP_contains_pte (1<<_GNTMAP_contains_pte) 510 511 /* 512 * Bits to be placed in guest kernel available PTE bits (architecture 513 * dependent; only supported when XENFEAT_gnttab_map_avail_bits is set). 514 */ 515 #define _GNTMAP_guest_avail0 (16) 516 #define GNTMAP_guest_avail_mask ((uint32_t)~0 << _GNTMAP_guest_avail0) 517 518 /* 519 * Values for error status returns. All errors are -ve. 520 */ 521 #define GNTST_okay (0) /* Normal return. */ 522 #define GNTST_general_error (-1) /* General undefined error. */ 523 #define GNTST_bad_domain (-2) /* Unrecognsed domain id. */ 524 #define GNTST_bad_gntref (-3) /* Unrecognised or inappropriate gntref. */ 525 #define GNTST_bad_handle (-4) /* Unrecognised or inappropriate handle. */ 526 #define GNTST_bad_virt_addr (-5) /* Inappropriate virtual address to map. */ 527 #define GNTST_bad_dev_addr (-6) /* Inappropriate device address to unmap.*/ 528 #define GNTST_no_device_space (-7) /* Out of space in I/O MMU. */ 529 #define GNTST_permission_denied (-8) /* Not enough privilege for operation. */ 530 #define GNTST_bad_page (-9) /* Specified page was invalid for op. */ 531 #define GNTST_bad_copy_arg (-10) /* copy arguments cross page boundary. */ 532 #define GNTST_address_too_big (-11) /* transfer page address too large. */ 533 #define GNTST_eagain (-12) /* Operation not done; try again. */ 534 535 #define GNTTABOP_error_msgs { \ 536 "okay", \ 537 "undefined error", \ 538 "unrecognised domain id", \ 539 "invalid grant reference", \ 540 "invalid mapping handle", \ 541 "invalid virtual address", \ 542 "invalid device address", \ 543 "no spare translation slot in the I/O MMU", \ 544 "permission denied", \ 545 "bad page", \ 546 "copy arguments cross page boundary", \ 547 "page address size too large", \ 548 "operation not done; try again" \ 549 } 550 551 #endif /* __XEN_PUBLIC_GRANT_TABLE_H__ */ 552