The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/xen/interface/grant_table.h

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    1 /******************************************************************************
    2  * grant_table.h
    3  * 
    4  * Interface for granting foreign access to page frames, and receiving
    5  * page-ownership transfers.
    6  * 
    7  * Permission is hereby granted, free of charge, to any person obtaining a copy
    8  * of this software and associated documentation files (the "Software"), to
    9  * deal in the Software without restriction, including without limitation the
   10  * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
   11  * sell copies of the Software, and to permit persons to whom the Software is
   12  * furnished to do so, subject to the following conditions:
   13  *
   14  * The above copyright notice and this permission notice shall be included in
   15  * all copies or substantial portions of the Software.
   16  *
   17  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   18  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
   19  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   20  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   21  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
   22  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
   23  * DEALINGS IN THE SOFTWARE.
   24  *
   25  * Copyright (c) 2004, K A Fraser
   26  */
   27 
   28 #ifndef __XEN_PUBLIC_GRANT_TABLE_H__
   29 #define __XEN_PUBLIC_GRANT_TABLE_H__
   30 
   31 
   32 /***********************************
   33  * GRANT TABLE REPRESENTATION
   34  */
   35 
   36 /* Some rough guidelines on accessing and updating grant-table entries
   37  * in a concurrency-safe manner. For more information, Linux contains a
   38  * reference implementation for guest OSes (arch/xen/kernel/grant_table.c).
   39  * 
   40  * NB. WMB is a no-op on current-generation x86 processors. However, a
   41  *     compiler barrier will still be required.
   42  * 
   43  * Introducing a valid entry into the grant table:
   44  *  1. Write ent->domid.
   45  *  2. Write ent->frame:
   46  *      GTF_permit_access:   Frame to which access is permitted.
   47  *      GTF_accept_transfer: Pseudo-phys frame slot being filled by new
   48  *                           frame, or zero if none.
   49  *  3. Write memory barrier (WMB).
   50  *  4. Write ent->flags, inc. valid type.
   51  * 
   52  * Invalidating an unused GTF_permit_access entry:
   53  *  1. flags = ent->flags.
   54  *  2. Observe that !(flags & (GTF_reading|GTF_writing)).
   55  *  3. Check result of SMP-safe CMPXCHG(&ent->flags, flags, 0).
   56  *  NB. No need for WMB as reuse of entry is control-dependent on success of
   57  *      step 3, and all architectures guarantee ordering of ctrl-dep writes.
   58  *
   59  * Invalidating an in-use GTF_permit_access entry:
   60  *  This cannot be done directly. Request assistance from the domain controller
   61  *  which can set a timeout on the use of a grant entry and take necessary
   62  *  action. (NB. This is not yet implemented!).
   63  * 
   64  * Invalidating an unused GTF_accept_transfer entry:
   65  *  1. flags = ent->flags.
   66  *  2. Observe that !(flags & GTF_transfer_committed). [*]
   67  *  3. Check result of SMP-safe CMPXCHG(&ent->flags, flags, 0).
   68  *  NB. No need for WMB as reuse of entry is control-dependent on success of
   69  *      step 3, and all architectures guarantee ordering of ctrl-dep writes.
   70  *  [*] If GTF_transfer_committed is set then the grant entry is 'committed'.
   71  *      The guest must /not/ modify the grant entry until the address of the
   72  *      transferred frame is written. It is safe for the guest to spin waiting
   73  *      for this to occur (detect by observing GTF_transfer_completed in
   74  *      ent->flags).
   75  *
   76  * Invalidating a committed GTF_accept_transfer entry:
   77  *  1. Wait for (ent->flags & GTF_transfer_completed).
   78  *
   79  * Changing a GTF_permit_access from writable to read-only:
   80  *  Use SMP-safe CMPXCHG to set GTF_readonly, while checking !GTF_writing.
   81  * 
   82  * Changing a GTF_permit_access from read-only to writable:
   83  *  Use SMP-safe bit-setting instruction.
   84  */
   85 
   86 /*
   87  * A grant table comprises a packed array of grant entries in one or more
   88  * page frames shared between Xen and a guest.
   89  * [XEN]: This field is written by Xen and read by the sharing guest.
   90  * [GST]: This field is written by the guest and read by Xen.
   91  */
   92 struct grant_entry {
   93     /* GTF_xxx: various type and flag information.  [XEN,GST] */
   94     uint16_t flags;
   95     /* The domain being granted foreign privileges. [GST] */
   96     domid_t  domid;
   97     /*
   98      * GTF_permit_access: Frame that @domid is allowed to map and access. [GST]
   99      * GTF_accept_transfer: Frame whose ownership transferred by @domid. [XEN]
  100      */
  101     uint32_t frame;
  102 };
  103 typedef struct grant_entry grant_entry_t;
  104 
  105 /*
  106  * Type of grant entry.
  107  *  GTF_invalid: This grant entry grants no privileges.
  108  *  GTF_permit_access: Allow @domid to map/access @frame.
  109  *  GTF_accept_transfer: Allow @domid to transfer ownership of one page frame
  110  *                       to this guest. Xen writes the page number to @frame.
  111  */
  112 #define GTF_invalid         (0U<<0)
  113 #define GTF_permit_access   (1U<<0)
  114 #define GTF_accept_transfer (2U<<0)
  115 #define GTF_type_mask       (3U<<0)
  116 
  117 /*
  118  * Subflags for GTF_permit_access.
  119  *  GTF_readonly: Restrict @domid to read-only mappings and accesses. [GST]
  120  *  GTF_reading: Grant entry is currently mapped for reading by @domid. [XEN]
  121  *  GTF_writing: Grant entry is currently mapped for writing by @domid. [XEN]
  122  *  GTF_PAT, GTF_PWT, GTF_PCD: (x86) cache attribute flags for the grant [GST]
  123  */
  124 #define _GTF_readonly       (2)
  125 #define GTF_readonly        (1U<<_GTF_readonly)
  126 #define _GTF_reading        (3)
  127 #define GTF_reading         (1U<<_GTF_reading)
  128 #define _GTF_writing        (4)
  129 #define GTF_writing         (1U<<_GTF_writing)
  130 #define _GTF_PWT            (5)
  131 #define GTF_PWT             (1U<<_GTF_PWT)
  132 #define _GTF_PCD            (6)
  133 #define GTF_PCD             (1U<<_GTF_PCD)
  134 #define _GTF_PAT            (7)
  135 #define GTF_PAT             (1U<<_GTF_PAT)
  136 
  137 /*
  138  * Subflags for GTF_accept_transfer:
  139  *  GTF_transfer_committed: Xen sets this flag to indicate that it is committed
  140  *      to transferring ownership of a page frame. When a guest sees this flag
  141  *      it must /not/ modify the grant entry until GTF_transfer_completed is
  142  *      set by Xen.
  143  *  GTF_transfer_completed: It is safe for the guest to spin-wait on this flag
  144  *      after reading GTF_transfer_committed. Xen will always write the frame
  145  *      address, followed by ORing this flag, in a timely manner.
  146  */
  147 #define _GTF_transfer_committed (2)
  148 #define GTF_transfer_committed  (1U<<_GTF_transfer_committed)
  149 #define _GTF_transfer_completed (3)
  150 #define GTF_transfer_completed  (1U<<_GTF_transfer_completed)
  151 
  152 
  153 /***********************************
  154  * GRANT TABLE QUERIES AND USES
  155  */
  156 
  157 /*
  158  * Reference to a grant entry in a specified domain's grant table.
  159  */
  160 typedef uint32_t grant_ref_t;
  161 
  162 /*
  163  * Handle to track a mapping created via a grant reference.
  164  */
  165 typedef uint32_t grant_handle_t;
  166 
  167 /*
  168  * GNTTABOP_map_grant_ref: Map the grant entry (<dom>,<ref>) for access
  169  * by devices and/or host CPUs. If successful, <handle> is a tracking number
  170  * that must be presented later to destroy the mapping(s). On error, <handle>
  171  * is a negative status code.
  172  * NOTES:
  173  *  1. If GNTMAP_device_map is specified then <dev_bus_addr> is the address
  174  *     via which I/O devices may access the granted frame.
  175  *  2. If GNTMAP_host_map is specified then a mapping will be added at
  176  *     either a host virtual address in the current address space, or at
  177  *     a PTE at the specified machine address.  The type of mapping to
  178  *     perform is selected through the GNTMAP_contains_pte flag, and the 
  179  *     address is specified in <host_addr>.
  180  *  3. Mappings should only be destroyed via GNTTABOP_unmap_grant_ref. If a
  181  *     host mapping is destroyed by other means then it is *NOT* guaranteed
  182  *     to be accounted to the correct grant reference!
  183  */
  184 #define GNTTABOP_map_grant_ref        0
  185 struct gnttab_map_grant_ref {
  186     /* IN parameters. */
  187     uint64_t host_addr;
  188     uint32_t flags;               /* GNTMAP_* */
  189     grant_ref_t ref;
  190     domid_t  dom;
  191     /* OUT parameters. */
  192     int16_t  status;              /* GNTST_* */
  193     grant_handle_t handle;
  194     uint64_t dev_bus_addr;
  195 };
  196 typedef struct gnttab_map_grant_ref gnttab_map_grant_ref_t;
  197 DEFINE_XEN_GUEST_HANDLE(gnttab_map_grant_ref_t);
  198 
  199 /*
  200  * GNTTABOP_unmap_grant_ref: Destroy one or more grant-reference mappings
  201  * tracked by <handle>. If <host_addr> or <dev_bus_addr> is zero, that
  202  * field is ignored. If non-zero, they must refer to a device/host mapping
  203  * that is tracked by <handle>
  204  * NOTES:
  205  *  1. The call may fail in an undefined manner if either mapping is not
  206  *     tracked by <handle>.
  207  *  3. After executing a batch of unmaps, it is guaranteed that no stale
  208  *     mappings will remain in the device or host TLBs.
  209  */
  210 #define GNTTABOP_unmap_grant_ref      1
  211 struct gnttab_unmap_grant_ref {
  212     /* IN parameters. */
  213     uint64_t host_addr;
  214     uint64_t dev_bus_addr;
  215     grant_handle_t handle;
  216     /* OUT parameters. */
  217     int16_t  status;              /* GNTST_* */
  218 };
  219 typedef struct gnttab_unmap_grant_ref gnttab_unmap_grant_ref_t;
  220 DEFINE_XEN_GUEST_HANDLE(gnttab_unmap_grant_ref_t);
  221 
  222 /*
  223  * GNTTABOP_setup_table: Set up a grant table for <dom> comprising at least
  224  * <nr_frames> pages. The frame addresses are written to the <frame_list>.
  225  * Only <nr_frames> addresses are written, even if the table is larger.
  226  * NOTES:
  227  *  1. <dom> may be specified as DOMID_SELF.
  228  *  2. Only a sufficiently-privileged domain may specify <dom> != DOMID_SELF.
  229  *  3. Xen may not support more than a single grant-table page per domain.
  230  */
  231 #define GNTTABOP_setup_table          2
  232 struct gnttab_setup_table {
  233     /* IN parameters. */
  234     domid_t  dom;
  235     uint32_t nr_frames;
  236     /* OUT parameters. */
  237     int16_t  status;              /* GNTST_* */
  238     XEN_GUEST_HANDLE(ulong) frame_list;
  239 };
  240 typedef struct gnttab_setup_table gnttab_setup_table_t;
  241 DEFINE_XEN_GUEST_HANDLE(gnttab_setup_table_t);
  242 
  243 /*
  244  * GNTTABOP_dump_table: Dump the contents of the grant table to the
  245  * xen console. Debugging use only.
  246  */
  247 #define GNTTABOP_dump_table           3
  248 struct gnttab_dump_table {
  249     /* IN parameters. */
  250     domid_t dom;
  251     /* OUT parameters. */
  252     int16_t status;               /* GNTST_* */
  253 };
  254 typedef struct gnttab_dump_table gnttab_dump_table_t;
  255 DEFINE_XEN_GUEST_HANDLE(gnttab_dump_table_t);
  256 
  257 /*
  258  * GNTTABOP_transfer_grant_ref: Transfer <frame> to a foreign domain. The
  259  * foreign domain has previously registered its interest in the transfer via
  260  * <domid, ref>.
  261  * 
  262  * Note that, even if the transfer fails, the specified page no longer belongs
  263  * to the calling domain *unless* the error is GNTST_bad_page.
  264  */
  265 #define GNTTABOP_transfer                4
  266 struct gnttab_transfer {
  267     /* IN parameters. */
  268     xen_pfn_t     mfn;
  269     domid_t       domid;
  270     grant_ref_t   ref;
  271     /* OUT parameters. */
  272     int16_t       status;
  273 };
  274 typedef struct gnttab_transfer gnttab_transfer_t;
  275 DEFINE_XEN_GUEST_HANDLE(gnttab_transfer_t);
  276 
  277 
  278 /*
  279  * GNTTABOP_copy: Hypervisor based copy
  280  * source and destinations can be eithers MFNs or, for foreign domains,
  281  * grant references. the foreign domain has to grant read/write access
  282  * in its grant table.
  283  *
  284  * The flags specify what type source and destinations are (either MFN
  285  * or grant reference).
  286  *
  287  * Note that this can also be used to copy data between two domains
  288  * via a third party if the source and destination domains had previously
  289  * grant appropriate access to their pages to the third party.
  290  *
  291  * source_offset specifies an offset in the source frame, dest_offset
  292  * the offset in the target frame and  len specifies the number of
  293  * bytes to be copied.
  294  */
  295 
  296 #define _GNTCOPY_source_gref      (0)
  297 #define GNTCOPY_source_gref       (1<<_GNTCOPY_source_gref)
  298 #define _GNTCOPY_dest_gref        (1)
  299 #define GNTCOPY_dest_gref         (1<<_GNTCOPY_dest_gref)
  300 
  301 #define GNTTABOP_copy                 5
  302 typedef struct gnttab_copy {
  303     /* IN parameters. */
  304     struct {
  305         union {
  306             grant_ref_t ref;
  307             xen_pfn_t   gmfn;
  308         } u;
  309         domid_t  domid;
  310         uint16_t offset;
  311     } source, dest;
  312     uint16_t      len;
  313     uint16_t      flags;          /* GNTCOPY_* */
  314     /* OUT parameters. */
  315     int16_t       status;
  316 } gnttab_copy_t;
  317 DEFINE_XEN_GUEST_HANDLE(gnttab_copy_t);
  318 
  319 /*
  320  * GNTTABOP_query_size: Query the current and maximum sizes of the shared
  321  * grant table.
  322  * NOTES:
  323  *  1. <dom> may be specified as DOMID_SELF.
  324  *  2. Only a sufficiently-privileged domain may specify <dom> != DOMID_SELF.
  325  */
  326 #define GNTTABOP_query_size           6
  327 struct gnttab_query_size {
  328     /* IN parameters. */
  329     domid_t  dom;
  330     /* OUT parameters. */
  331     uint32_t nr_frames;
  332     uint32_t max_nr_frames;
  333     int16_t  status;              /* GNTST_* */
  334 };
  335 typedef struct gnttab_query_size gnttab_query_size_t;
  336 DEFINE_XEN_GUEST_HANDLE(gnttab_query_size_t);
  337 
  338 /*
  339  * GNTTABOP_unmap_and_replace: Destroy one or more grant-reference mappings
  340  * tracked by <handle> but atomically replace the page table entry with one
  341  * pointing to the machine address under <new_addr>.  <new_addr> will be
  342  * redirected to the null entry.
  343  * NOTES:
  344  *  1. The call may fail in an undefined manner if either mapping is not
  345  *     tracked by <handle>.
  346  *  2. After executing a batch of unmaps, it is guaranteed that no stale
  347  *     mappings will remain in the device or host TLBs.
  348  */
  349 #define GNTTABOP_unmap_and_replace    7
  350 struct gnttab_unmap_and_replace {
  351     /* IN parameters. */
  352     uint64_t host_addr;
  353     uint64_t new_addr;
  354     grant_handle_t handle;
  355     /* OUT parameters. */
  356     int16_t  status;              /* GNTST_* */
  357 };
  358 typedef struct gnttab_unmap_and_replace gnttab_unmap_and_replace_t;
  359 DEFINE_XEN_GUEST_HANDLE(gnttab_unmap_and_replace_t);
  360 
  361 
  362 /*
  363  * Bitfield values for update_pin_status.flags.
  364  */
  365  /* Map the grant entry for access by I/O devices. */
  366 #define _GNTMAP_device_map      (0)
  367 #define GNTMAP_device_map       (1<<_GNTMAP_device_map)
  368  /* Map the grant entry for access by host CPUs. */
  369 #define _GNTMAP_host_map        (1)
  370 #define GNTMAP_host_map         (1<<_GNTMAP_host_map)
  371  /* Accesses to the granted frame will be restricted to read-only access. */
  372 #define _GNTMAP_readonly        (2)
  373 #define GNTMAP_readonly         (1<<_GNTMAP_readonly)
  374  /*
  375   * GNTMAP_host_map subflag:
  376   *  0 => The host mapping is usable only by the guest OS.
  377   *  1 => The host mapping is usable by guest OS + current application.
  378   */
  379 #define _GNTMAP_application_map (3)
  380 #define GNTMAP_application_map  (1<<_GNTMAP_application_map)
  381 
  382  /*
  383   * GNTMAP_contains_pte subflag:
  384   *  0 => This map request contains a host virtual address.
  385   *  1 => This map request contains the machine addess of the PTE to update.
  386   */
  387 #define _GNTMAP_contains_pte    (4)
  388 #define GNTMAP_contains_pte     (1<<_GNTMAP_contains_pte)
  389 
  390 /*
  391  * Values for error status returns. All errors are -ve.
  392  */
  393 #define GNTST_okay             (0)  /* Normal return.                        */
  394 #define GNTST_general_error    (-1) /* General undefined error.              */
  395 #define GNTST_bad_domain       (-2) /* Unrecognsed domain id.                */
  396 #define GNTST_bad_gntref       (-3) /* Unrecognised or inappropriate gntref. */
  397 #define GNTST_bad_handle       (-4) /* Unrecognised or inappropriate handle. */
  398 #define GNTST_bad_virt_addr    (-5) /* Inappropriate virtual address to map. */
  399 #define GNTST_bad_dev_addr     (-6) /* Inappropriate device address to unmap.*/
  400 #define GNTST_no_device_space  (-7) /* Out of space in I/O MMU.              */
  401 #define GNTST_permission_denied (-8) /* Not enough privilege for operation.  */
  402 #define GNTST_bad_page         (-9) /* Specified page was invalid for op.    */
  403 #define GNTST_bad_copy_arg    (-10) /* copy arguments cross page boundary.   */
  404 #define GNTST_address_too_big (-11) /* transfer page address too large.      */
  405 
  406 #define GNTTABOP_error_msgs {                   \
  407     "okay",                                     \
  408     "undefined error",                          \
  409     "unrecognised domain id",                   \
  410     "invalid grant reference",                  \
  411     "invalid mapping handle",                   \
  412     "invalid virtual address",                  \
  413     "invalid device address",                   \
  414     "no spare translation slot in the I/O MMU", \
  415     "permission denied",                        \
  416     "bad page",                                 \
  417     "copy arguments cross page boundary",       \
  418     "page address size too large"               \
  419 }
  420 
  421 #endif /* __XEN_PUBLIC_GRANT_TABLE_H__ */
  422 
  423 /*
  424  * Local variables:
  425  * mode: C
  426  * c-set-style: "BSD"
  427  * c-basic-offset: 4
  428  * tab-width: 4
  429  * indent-tabs-mode: nil
  430  * End:
  431  */

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