grant_table.h (21568B)
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 (drivers/xen/grant_table.c, see 23 * http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=blob;f=drivers/xen/grant-table.c;hb=HEAD 24 * 25 * NB. WMB is a no-op on current-generation x86 processors. However, a 26 * compiler barrier will still be required. 27 * 28 * Introducing a valid entry into the grant table: 29 * 1. Write ent->domid. 30 * 2. Write ent->frame: 31 * GTF_permit_access: Frame to which access is permitted. 32 * GTF_accept_transfer: Pseudo-phys frame slot being filled by new 33 * frame, or zero if none. 34 * 3. Write memory barrier (WMB). 35 * 4. Write ent->flags, inc. valid type. 36 * 37 * Invalidating an unused GTF_permit_access entry: 38 * 1. flags = ent->flags. 39 * 2. Observe that !(flags & (GTF_reading|GTF_writing)). 40 * 3. Check result of SMP-safe CMPXCHG(&ent->flags, flags, 0). 41 * NB. No need for WMB as reuse of entry is control-dependent on success of 42 * step 3, and all architectures guarantee ordering of ctrl-dep writes. 43 * 44 * Invalidating an in-use GTF_permit_access entry: 45 * This cannot be done directly. Request assistance from the domain controller 46 * which can set a timeout on the use of a grant entry and take necessary 47 * action. (NB. This is not yet implemented!). 48 * 49 * Invalidating an unused GTF_accept_transfer entry: 50 * 1. flags = ent->flags. 51 * 2. Observe that !(flags & GTF_transfer_committed). [*] 52 * 3. Check result of SMP-safe CMPXCHG(&ent->flags, flags, 0). 53 * NB. No need for WMB as reuse of entry is control-dependent on success of 54 * step 3, and all architectures guarantee ordering of ctrl-dep writes. 55 * [*] If GTF_transfer_committed is set then the grant entry is 'committed'. 56 * The guest must /not/ modify the grant entry until the address of the 57 * transferred frame is written. It is safe for the guest to spin waiting 58 * for this to occur (detect by observing GTF_transfer_completed in 59 * ent->flags). 60 * 61 * Invalidating a committed GTF_accept_transfer entry: 62 * 1. Wait for (ent->flags & GTF_transfer_completed). 63 * 64 * Changing a GTF_permit_access from writable to read-only: 65 * Use SMP-safe CMPXCHG to set GTF_readonly, while checking !GTF_writing. 66 * 67 * Changing a GTF_permit_access from read-only to writable: 68 * Use SMP-safe bit-setting instruction. 69 */ 70 71/* 72 * Reference to a grant entry in a specified domain's grant table. 73 */ 74typedef uint32_t grant_ref_t; 75 76/* 77 * A grant table comprises a packed array of grant entries in one or more 78 * page frames shared between Xen and a guest. 79 * [XEN]: This field is written by Xen and read by the sharing guest. 80 * [GST]: This field is written by the guest and read by Xen. 81 */ 82 83/* 84 * Version 1 of the grant table entry structure is maintained largely for 85 * backwards compatibility. New guests are recommended to support using 86 * version 2 to overcome version 1 limitations, but to default to version 1. 87 */ 88struct grant_entry_v1 { 89 /* GTF_xxx: various type and flag information. [XEN,GST] */ 90 uint16_t flags; 91 /* The domain being granted foreign privileges. [GST] */ 92 domid_t domid; 93 /* 94 * GTF_permit_access: GFN that @domid is allowed to map and access. [GST] 95 * GTF_accept_transfer: GFN that @domid is allowed to transfer into. [GST] 96 * GTF_transfer_completed: MFN whose ownership transferred by @domid 97 * (non-translated guests only). [XEN] 98 */ 99 uint32_t frame; 100}; 101 102/* The first few grant table entries will be preserved across grant table 103 * version changes and may be pre-populated at domain creation by tools. 104 */ 105#define GNTTAB_NR_RESERVED_ENTRIES 8 106#define GNTTAB_RESERVED_CONSOLE 0 107#define GNTTAB_RESERVED_XENSTORE 1 108 109/* 110 * Type of grant entry. 111 * GTF_invalid: This grant entry grants no privileges. 112 * GTF_permit_access: Allow @domid to map/access @frame. 113 * GTF_accept_transfer: Allow @domid to transfer ownership of one page frame 114 * to this guest. Xen writes the page number to @frame. 115 * GTF_transitive: Allow @domid to transitively access a subrange of 116 * @trans_grant in @trans_domid. No mappings are allowed. 117 */ 118#define GTF_invalid (0U<<0) 119#define GTF_permit_access (1U<<0) 120#define GTF_accept_transfer (2U<<0) 121#define GTF_transitive (3U<<0) 122#define GTF_type_mask (3U<<0) 123 124/* 125 * Subflags for GTF_permit_access and GTF_transitive. 126 * GTF_readonly: Restrict @domid to read-only mappings and accesses. [GST] 127 * GTF_reading: Grant entry is currently mapped for reading by @domid. [XEN] 128 * GTF_writing: Grant entry is currently mapped for writing by @domid. [XEN] 129 * Further subflags for GTF_permit_access only. 130 * GTF_PAT, GTF_PWT, GTF_PCD: (x86) cache attribute flags to be used for 131 * mappings of the grant [GST] 132 * GTF_sub_page: Grant access to only a subrange of the page. @domid 133 * will only be allowed to copy from the grant, and not 134 * map it. [GST] 135 */ 136#define _GTF_readonly (2) 137#define GTF_readonly (1U<<_GTF_readonly) 138#define _GTF_reading (3) 139#define GTF_reading (1U<<_GTF_reading) 140#define _GTF_writing (4) 141#define GTF_writing (1U<<_GTF_writing) 142#define _GTF_PWT (5) 143#define GTF_PWT (1U<<_GTF_PWT) 144#define _GTF_PCD (6) 145#define GTF_PCD (1U<<_GTF_PCD) 146#define _GTF_PAT (7) 147#define GTF_PAT (1U<<_GTF_PAT) 148#define _GTF_sub_page (8) 149#define GTF_sub_page (1U<<_GTF_sub_page) 150 151/* 152 * Subflags for GTF_accept_transfer: 153 * GTF_transfer_committed: Xen sets this flag to indicate that it is committed 154 * to transferring ownership of a page frame. When a guest sees this flag 155 * it must /not/ modify the grant entry until GTF_transfer_completed is 156 * set by Xen. 157 * GTF_transfer_completed: It is safe for the guest to spin-wait on this flag 158 * after reading GTF_transfer_committed. Xen will always write the frame 159 * address, followed by ORing this flag, in a timely manner. 160 */ 161#define _GTF_transfer_committed (2) 162#define GTF_transfer_committed (1U<<_GTF_transfer_committed) 163#define _GTF_transfer_completed (3) 164#define GTF_transfer_completed (1U<<_GTF_transfer_completed) 165 166/* 167 * Version 2 grant table entries. These fulfil the same role as 168 * version 1 entries, but can represent more complicated operations. 169 * Any given domain will have either a version 1 or a version 2 table, 170 * and every entry in the table will be the same version. 171 * 172 * The interface by which domains use grant references does not depend 173 * on the grant table version in use by the other domain. 174 */ 175 176/* 177 * Version 1 and version 2 grant entries share a common prefix. The 178 * fields of the prefix are documented as part of struct 179 * grant_entry_v1. 180 */ 181struct grant_entry_header { 182 uint16_t flags; 183 domid_t domid; 184}; 185 186/* 187 * Version 2 of the grant entry structure. 188 */ 189union grant_entry_v2 { 190 struct grant_entry_header hdr; 191 192 /* 193 * This member is used for V1-style full page grants, where either: 194 * 195 * -- hdr.type is GTF_accept_transfer, or 196 * -- hdr.type is GTF_permit_access and GTF_sub_page is not set. 197 * 198 * In that case, the frame field has the same semantics as the 199 * field of the same name in the V1 entry structure. 200 */ 201 struct { 202 struct grant_entry_header hdr; 203 uint32_t pad0; 204 uint64_t frame; 205 } full_page; 206 207 /* 208 * If the grant type is GTF_grant_access and GTF_sub_page is set, 209 * @domid is allowed to access bytes [@page_off,@page_off+@length) 210 * in frame @frame. 211 */ 212 struct { 213 struct grant_entry_header hdr; 214 uint16_t page_off; 215 uint16_t length; 216 uint64_t frame; 217 } sub_page; 218 219 /* 220 * If the grant is GTF_transitive, @domid is allowed to use the 221 * grant @gref in domain @trans_domid, as if it was the local 222 * domain. Obviously, the transitive access must be compatible 223 * with the original grant. 224 * 225 * The current version of Xen does not allow transitive grants 226 * to be mapped. 227 */ 228 struct { 229 struct grant_entry_header hdr; 230 domid_t trans_domid; 231 uint16_t pad0; 232 grant_ref_t gref; 233 } transitive; 234 235 uint32_t __spacer[4]; /* Pad to a power of two */ 236}; 237 238typedef uint16_t grant_status_t; 239 240/*********************************** 241 * GRANT TABLE QUERIES AND USES 242 */ 243 244#define GNTTABOP_map_grant_ref 0 245#define GNTTABOP_unmap_grant_ref 1 246#define GNTTABOP_setup_table 2 247#define GNTTABOP_dump_table 3 248#define GNTTABOP_transfer 4 249#define GNTTABOP_copy 5 250#define GNTTABOP_query_size 6 251#define GNTTABOP_unmap_and_replace 7 252#define GNTTABOP_set_version 8 253#define GNTTABOP_get_status_frames 9 254#define GNTTABOP_get_version 10 255#define GNTTABOP_swap_grant_ref 11 256#define GNTTABOP_cache_flush 12 257/* ` } */ 258 259/* 260 * Handle to track a mapping created via a grant reference. 261 */ 262typedef uint32_t grant_handle_t; 263 264/* 265 * GNTTABOP_map_grant_ref: Map the grant entry (<dom>,<ref>) for access 266 * by devices and/or host CPUs. If successful, <handle> is a tracking number 267 * that must be presented later to destroy the mapping(s). On error, <status> 268 * is a negative status code. 269 * NOTES: 270 * 1. If GNTMAP_device_map is specified then <dev_bus_addr> is the address 271 * via which I/O devices may access the granted frame. 272 * 2. If GNTMAP_host_map is specified then a mapping will be added at 273 * either a host virtual address in the current address space, or at 274 * a PTE at the specified machine address. The type of mapping to 275 * perform is selected through the GNTMAP_contains_pte flag, and the 276 * address is specified in <host_addr>. 277 * 3. Mappings should only be destroyed via GNTTABOP_unmap_grant_ref. If a 278 * host mapping is destroyed by other means then it is *NOT* guaranteed 279 * to be accounted to the correct grant reference! 280 */ 281struct gnttab_map_grant_ref { 282 /* IN parameters. */ 283 uint64_t host_addr; 284 uint32_t flags; /* GNTMAP_* */ 285 grant_ref_t ref; 286 domid_t dom; 287 /* OUT parameters. */ 288 int16_t status; /* GNTST_* */ 289 grant_handle_t handle; 290 uint64_t dev_bus_addr; 291}; 292DEFINE_GUEST_HANDLE_STRUCT(gnttab_map_grant_ref); 293 294/* 295 * GNTTABOP_unmap_grant_ref: Destroy one or more grant-reference mappings 296 * tracked by <handle>. If <host_addr> or <dev_bus_addr> is zero, that 297 * field is ignored. If non-zero, they must refer to a device/host mapping 298 * that is tracked by <handle> 299 * NOTES: 300 * 1. The call may fail in an undefined manner if either mapping is not 301 * tracked by <handle>. 302 * 3. After executing a batch of unmaps, it is guaranteed that no stale 303 * mappings will remain in the device or host TLBs. 304 */ 305struct gnttab_unmap_grant_ref { 306 /* IN parameters. */ 307 uint64_t host_addr; 308 uint64_t dev_bus_addr; 309 grant_handle_t handle; 310 /* OUT parameters. */ 311 int16_t status; /* GNTST_* */ 312}; 313DEFINE_GUEST_HANDLE_STRUCT(gnttab_unmap_grant_ref); 314 315/* 316 * GNTTABOP_setup_table: Set up a grant table for <dom> comprising at least 317 * <nr_frames> pages. The frame addresses are written to the <frame_list>. 318 * Only <nr_frames> addresses are written, even if the table is larger. 319 * NOTES: 320 * 1. <dom> may be specified as DOMID_SELF. 321 * 2. Only a sufficiently-privileged domain may specify <dom> != DOMID_SELF. 322 * 3. Xen may not support more than a single grant-table page per domain. 323 */ 324struct gnttab_setup_table { 325 /* IN parameters. */ 326 domid_t dom; 327 uint32_t nr_frames; 328 /* OUT parameters. */ 329 int16_t status; /* GNTST_* */ 330 GUEST_HANDLE(xen_pfn_t) frame_list; 331}; 332DEFINE_GUEST_HANDLE_STRUCT(gnttab_setup_table); 333 334/* 335 * GNTTABOP_dump_table: Dump the contents of the grant table to the 336 * xen console. Debugging use only. 337 */ 338struct gnttab_dump_table { 339 /* IN parameters. */ 340 domid_t dom; 341 /* OUT parameters. */ 342 int16_t status; /* GNTST_* */ 343}; 344DEFINE_GUEST_HANDLE_STRUCT(gnttab_dump_table); 345 346/* 347 * GNTTABOP_transfer: Transfer <frame> to a foreign domain. The foreign domain 348 * has previously registered its interest in the transfer via <domid, ref>. 349 * 350 * Note that, even if the transfer fails, the specified page no longer belongs 351 * to the calling domain *unless* the error is GNTST_bad_page. 352 * 353 * Note further that only PV guests can use this operation. 354 */ 355struct gnttab_transfer { 356 /* IN parameters. */ 357 xen_pfn_t mfn; 358 domid_t domid; 359 grant_ref_t ref; 360 /* OUT parameters. */ 361 int16_t status; 362}; 363DEFINE_GUEST_HANDLE_STRUCT(gnttab_transfer); 364 365/* 366 * GNTTABOP_copy: Hypervisor based copy 367 * source and destinations can be eithers MFNs or, for foreign domains, 368 * grant references. the foreign domain has to grant read/write access 369 * in its grant table. 370 * 371 * The flags specify what type source and destinations are (either MFN 372 * or grant reference). 373 * 374 * Note that this can also be used to copy data between two domains 375 * via a third party if the source and destination domains had previously 376 * grant appropriate access to their pages to the third party. 377 * 378 * source_offset specifies an offset in the source frame, dest_offset 379 * the offset in the target frame and len specifies the number of 380 * bytes to be copied. 381 */ 382 383#define _GNTCOPY_source_gref (0) 384#define GNTCOPY_source_gref (1<<_GNTCOPY_source_gref) 385#define _GNTCOPY_dest_gref (1) 386#define GNTCOPY_dest_gref (1<<_GNTCOPY_dest_gref) 387 388struct gnttab_copy { 389 /* IN parameters. */ 390 struct gnttab_copy_ptr { 391 union { 392 grant_ref_t ref; 393 xen_pfn_t gmfn; 394 } u; 395 domid_t domid; 396 uint16_t offset; 397 } source, dest; 398 uint16_t len; 399 uint16_t flags; /* GNTCOPY_* */ 400 /* OUT parameters. */ 401 int16_t status; 402}; 403DEFINE_GUEST_HANDLE_STRUCT(gnttab_copy); 404 405/* 406 * GNTTABOP_query_size: Query the current and maximum sizes of the shared 407 * grant table. 408 * NOTES: 409 * 1. <dom> may be specified as DOMID_SELF. 410 * 2. Only a sufficiently-privileged domain may specify <dom> != DOMID_SELF. 411 */ 412struct gnttab_query_size { 413 /* IN parameters. */ 414 domid_t dom; 415 /* OUT parameters. */ 416 uint32_t nr_frames; 417 uint32_t max_nr_frames; 418 int16_t status; /* GNTST_* */ 419}; 420DEFINE_GUEST_HANDLE_STRUCT(gnttab_query_size); 421 422/* 423 * GNTTABOP_unmap_and_replace: Destroy one or more grant-reference mappings 424 * tracked by <handle> but atomically replace the page table entry with one 425 * pointing to the machine address under <new_addr>. <new_addr> will be 426 * redirected to the null entry. 427 * NOTES: 428 * 1. The call may fail in an undefined manner if either mapping is not 429 * tracked by <handle>. 430 * 2. After executing a batch of unmaps, it is guaranteed that no stale 431 * mappings will remain in the device or host TLBs. 432 */ 433struct gnttab_unmap_and_replace { 434 /* IN parameters. */ 435 uint64_t host_addr; 436 uint64_t new_addr; 437 grant_handle_t handle; 438 /* OUT parameters. */ 439 int16_t status; /* GNTST_* */ 440}; 441DEFINE_GUEST_HANDLE_STRUCT(gnttab_unmap_and_replace); 442 443/* 444 * GNTTABOP_set_version: Request a particular version of the grant 445 * table shared table structure. This operation may be used to toggle 446 * between different versions, but must be performed while no grants 447 * are active. The only defined versions are 1 and 2. 448 */ 449struct gnttab_set_version { 450 /* IN/OUT parameters */ 451 uint32_t version; 452}; 453DEFINE_GUEST_HANDLE_STRUCT(gnttab_set_version); 454 455/* 456 * GNTTABOP_get_status_frames: Get the list of frames used to store grant 457 * status for <dom>. In grant format version 2, the status is separated 458 * from the other shared grant fields to allow more efficient synchronization 459 * using barriers instead of atomic cmpexch operations. 460 * <nr_frames> specify the size of vector <frame_list>. 461 * The frame addresses are returned in the <frame_list>. 462 * Only <nr_frames> addresses are returned, even if the table is larger. 463 * NOTES: 464 * 1. <dom> may be specified as DOMID_SELF. 465 * 2. Only a sufficiently-privileged domain may specify <dom> != DOMID_SELF. 466 */ 467struct gnttab_get_status_frames { 468 /* IN parameters. */ 469 uint32_t nr_frames; 470 domid_t dom; 471 /* OUT parameters. */ 472 int16_t status; /* GNTST_* */ 473 GUEST_HANDLE(uint64_t) frame_list; 474}; 475DEFINE_GUEST_HANDLE_STRUCT(gnttab_get_status_frames); 476 477/* 478 * GNTTABOP_get_version: Get the grant table version which is in 479 * effect for domain <dom>. 480 */ 481struct gnttab_get_version { 482 /* IN parameters */ 483 domid_t dom; 484 uint16_t pad; 485 /* OUT parameters */ 486 uint32_t version; 487}; 488DEFINE_GUEST_HANDLE_STRUCT(gnttab_get_version); 489 490/* 491 * GNTTABOP_swap_grant_ref: Swap the contents of two grant entries. 492 */ 493struct gnttab_swap_grant_ref { 494 /* IN parameters */ 495 grant_ref_t ref_a; 496 grant_ref_t ref_b; 497 /* OUT parameters */ 498 int16_t status; /* GNTST_* */ 499}; 500DEFINE_GUEST_HANDLE_STRUCT(gnttab_swap_grant_ref); 501 502/* 503 * Issue one or more cache maintenance operations on a portion of a 504 * page granted to the calling domain by a foreign domain. 505 */ 506struct gnttab_cache_flush { 507 union { 508 uint64_t dev_bus_addr; 509 grant_ref_t ref; 510 } a; 511 uint16_t offset; /* offset from start of grant */ 512 uint16_t length; /* size within the grant */ 513#define GNTTAB_CACHE_CLEAN (1u<<0) 514#define GNTTAB_CACHE_INVAL (1u<<1) 515#define GNTTAB_CACHE_SOURCE_GREF (1u<<31) 516 uint32_t op; 517}; 518DEFINE_GUEST_HANDLE_STRUCT(gnttab_cache_flush); 519 520/* 521 * Bitfield values for gnttab_map_grant_ref.flags. 522 */ 523 /* Map the grant entry for access by I/O devices. */ 524#define _GNTMAP_device_map (0) 525#define GNTMAP_device_map (1<<_GNTMAP_device_map) 526 /* Map the grant entry for access by host CPUs. */ 527#define _GNTMAP_host_map (1) 528#define GNTMAP_host_map (1<<_GNTMAP_host_map) 529 /* Accesses to the granted frame will be restricted to read-only access. */ 530#define _GNTMAP_readonly (2) 531#define GNTMAP_readonly (1<<_GNTMAP_readonly) 532 /* 533 * GNTMAP_host_map subflag: 534 * 0 => The host mapping is usable only by the guest OS. 535 * 1 => The host mapping is usable by guest OS + current application. 536 */ 537#define _GNTMAP_application_map (3) 538#define GNTMAP_application_map (1<<_GNTMAP_application_map) 539 540 /* 541 * GNTMAP_contains_pte subflag: 542 * 0 => This map request contains a host virtual address. 543 * 1 => This map request contains the machine addess of the PTE to update. 544 */ 545#define _GNTMAP_contains_pte (4) 546#define GNTMAP_contains_pte (1<<_GNTMAP_contains_pte) 547 548/* 549 * Bits to be placed in guest kernel available PTE bits (architecture 550 * dependent; only supported when XENFEAT_gnttab_map_avail_bits is set). 551 */ 552#define _GNTMAP_guest_avail0 (16) 553#define GNTMAP_guest_avail_mask ((uint32_t)~0 << _GNTMAP_guest_avail0) 554 555/* 556 * Values for error status returns. All errors are -ve. 557 */ 558#define GNTST_okay (0) /* Normal return. */ 559#define GNTST_general_error (-1) /* General undefined error. */ 560#define GNTST_bad_domain (-2) /* Unrecognsed domain id. */ 561#define GNTST_bad_gntref (-3) /* Unrecognised or inappropriate gntref. */ 562#define GNTST_bad_handle (-4) /* Unrecognised or inappropriate handle. */ 563#define GNTST_bad_virt_addr (-5) /* Inappropriate virtual address to map. */ 564#define GNTST_bad_dev_addr (-6) /* Inappropriate device address to unmap.*/ 565#define GNTST_no_device_space (-7) /* Out of space in I/O MMU. */ 566#define GNTST_permission_denied (-8) /* Not enough privilege for operation. */ 567#define GNTST_bad_page (-9) /* Specified page was invalid for op. */ 568#define GNTST_bad_copy_arg (-10) /* copy arguments cross page boundary. */ 569#define GNTST_address_too_big (-11) /* transfer page address too large. */ 570#define GNTST_eagain (-12) /* Operation not done; try again. */ 571#define GNTST_no_space (-13) /* Out of space (handles etc). */ 572 573#define GNTTABOP_error_msgs { \ 574 "okay", \ 575 "undefined error", \ 576 "unrecognised domain id", \ 577 "invalid grant reference", \ 578 "invalid mapping handle", \ 579 "invalid virtual address", \ 580 "invalid device address", \ 581 "no spare translation slot in the I/O MMU", \ 582 "permission denied", \ 583 "bad page", \ 584 "copy arguments cross page boundary", \ 585 "page address size too large", \ 586 "operation not done; try again", \ 587 "out of space", \ 588} 589 590#endif /* __XEN_PUBLIC_GRANT_TABLE_H__ */