FreeBSD/Linux Kernel Cross Reference
sys/xen/interface/grant_table.h

     /******************************************************************************
      * grant_table.h
      * 
      * Interface for granting foreign access to page frames, and receiving
      * page-ownership transfers.
      * 
      * Permission is hereby granted, free of charge, to any person obtaining a copy
      * of this software and associated documentation files (the "Software"), to
      * deal in the Software without restriction, including without limitation the
     * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
     * sell copies of the Software, and to permit persons to whom the Software is
     * furnished to do so, subject to the following conditions:
     *
     * The above copyright notice and this permission notice shall be included in
     * all copies or substantial portions of the Software.
     *
     * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
     * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
     * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
     * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
     * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
     * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
     * DEALINGS IN THE SOFTWARE.
     *
     * Copyright (c) 2004, K A Fraser
     */
    
    #ifndef __XEN_PUBLIC_GRANT_TABLE_H__
    #define __XEN_PUBLIC_GRANT_TABLE_H__
    
    
    /***********************************
     * GRANT TABLE REPRESENTATION
     */
    
    /* Some rough guidelines on accessing and updating grant-table entries
     * in a concurrency-safe manner. For more information, Linux contains a
     * reference implementation for guest OSes (arch/xen/kernel/grant_table.c).
     * 
     * NB. WMB is a no-op on current-generation x86 processors. However, a
     *     compiler barrier will still be required.
     * 
     * Introducing a valid entry into the grant table:
     *  1. Write ent->domid.
     *  2. Write ent->frame:
     *      GTF_permit_access:   Frame to which access is permitted.
     *      GTF_accept_transfer: Pseudo-phys frame slot being filled by new
     *                           frame, or zero if none.
     *  3. Write memory barrier (WMB).
     *  4. Write ent->flags, inc. valid type.
     * 
     * Invalidating an unused GTF_permit_access entry:
     *  1. flags = ent->flags.
     *  2. Observe that !(flags & (GTF_reading|GTF_writing)).
     *  3. Check result of SMP-safe CMPXCHG(&ent->flags, flags, 0).
     *  NB. No need for WMB as reuse of entry is control-dependent on success of
     *      step 3, and all architectures guarantee ordering of ctrl-dep writes.
     *
     * Invalidating an in-use GTF_permit_access entry:
     *  This cannot be done directly. Request assistance from the domain controller
     *  which can set a timeout on the use of a grant entry and take necessary
     *  action. (NB. This is not yet implemented!).
     * 
     * Invalidating an unused GTF_accept_transfer entry:
     *  1. flags = ent->flags.
     *  2. Observe that !(flags & GTF_transfer_committed). [*]
     *  3. Check result of SMP-safe CMPXCHG(&ent->flags, flags, 0).
     *  NB. No need for WMB as reuse of entry is control-dependent on success of
     *      step 3, and all architectures guarantee ordering of ctrl-dep writes.
     *  [*] If GTF_transfer_committed is set then the grant entry is 'committed'.
     *      The guest must /not/ modify the grant entry until the address of the
     *      transferred frame is written. It is safe for the guest to spin waiting
     *      for this to occur (detect by observing GTF_transfer_completed in
     *      ent->flags).
     *
     * Invalidating a committed GTF_accept_transfer entry:
     *  1. Wait for (ent->flags & GTF_transfer_completed).
     *
     * Changing a GTF_permit_access from writable to read-only:
     *  Use SMP-safe CMPXCHG to set GTF_readonly, while checking !GTF_writing.
     * 
     * Changing a GTF_permit_access from read-only to writable:
     *  Use SMP-safe bit-setting instruction.
     */
    
    /*
     * A grant table comprises a packed array of grant entries in one or more
     * page frames shared between Xen and a guest.
     * [XEN]: This field is written by Xen and read by the sharing guest.
     * [GST]: This field is written by the guest and read by Xen.
     */
    struct grant_entry {
        /* GTF_xxx: various type and flag information.  [XEN,GST] */
        uint16_t flags;
        /* The domain being granted foreign privileges. [GST] */
        domid_t  domid;
        /*
         * GTF_permit_access: Frame that @domid is allowed to map and access. [GST]
         * GTF_accept_transfer: Frame whose ownership transferred by @domid. [XEN]
        */
       uint32_t frame;
   };
   typedef struct grant_entry grant_entry_t;
   
   /*
    * Type of grant entry.
    *  GTF_invalid: This grant entry grants no privileges.
    *  GTF_permit_access: Allow @domid to map/access @frame.
    *  GTF_accept_transfer: Allow @domid to transfer ownership of one page frame
    *                       to this guest. Xen writes the page number to @frame.
    */
   #define GTF_invalid         (0U<<0)
   #define GTF_permit_access   (1U<<0)
   #define GTF_accept_transfer (2U<<0)
   #define GTF_type_mask       (3U<<0)
   
   /*
    * Subflags for GTF_permit_access.
    *  GTF_readonly: Restrict @domid to read-only mappings and accesses. [GST]
    *  GTF_reading: Grant entry is currently mapped for reading by @domid. [XEN]
    *  GTF_writing: Grant entry is currently mapped for writing by @domid. [XEN]
    *  GTF_PAT, GTF_PWT, GTF_PCD: (x86) cache attribute flags for the grant [GST]
    */
   #define _GTF_readonly       (2)
   #define GTF_readonly        (1U<<_GTF_readonly)
   #define _GTF_reading        (3)
   #define GTF_reading         (1U<<_GTF_reading)
   #define _GTF_writing        (4)
   #define GTF_writing         (1U<<_GTF_writing)
   #define _GTF_PWT            (5)
   #define GTF_PWT             (1U<<_GTF_PWT)
   #define _GTF_PCD            (6)
   #define GTF_PCD             (1U<<_GTF_PCD)
   #define _GTF_PAT            (7)
   #define GTF_PAT             (1U<<_GTF_PAT)
   
   /*
    * Subflags for GTF_accept_transfer:
    *  GTF_transfer_committed: Xen sets this flag to indicate that it is committed
    *      to transferring ownership of a page frame. When a guest sees this flag
    *      it must /not/ modify the grant entry until GTF_transfer_completed is
    *      set by Xen.
    *  GTF_transfer_completed: It is safe for the guest to spin-wait on this flag
    *      after reading GTF_transfer_committed. Xen will always write the frame
    *      address, followed by ORing this flag, in a timely manner.
    */
   #define _GTF_transfer_committed (2)
   #define GTF_transfer_committed  (1U<<_GTF_transfer_committed)
   #define _GTF_transfer_completed (3)
   #define GTF_transfer_completed  (1U<<_GTF_transfer_completed)
   
   
   /***********************************
    * GRANT TABLE QUERIES AND USES
    */
   
   /*
    * Reference to a grant entry in a specified domain's grant table.
    */
   typedef uint32_t grant_ref_t;
   
   #define GRANT_REF_INVALID       0xffffffff
   
   /*
    * Handle to track a mapping created via a grant reference.
    */
   typedef uint32_t grant_handle_t;
   
   /*
    * GNTTABOP_map_grant_ref: Map the grant entry (<dom>,<ref>) for access
    * by devices and/or host CPUs. If successful, <handle> is a tracking number
    * that must be presented later to destroy the mapping(s). On error, <handle>
    * is a negative status code.
    * NOTES:
    *  1. If GNTMAP_device_map is specified then <dev_bus_addr> is the address
    *     via which I/O devices may access the granted frame.
    *  2. If GNTMAP_host_map is specified then a mapping will be added at
    *     either a host virtual address in the current address space, or at
    *     a PTE at the specified machine address.  The type of mapping to
    *     perform is selected through the GNTMAP_contains_pte flag, and the 
    *     address is specified in <host_addr>.
    *  3. Mappings should only be destroyed via GNTTABOP_unmap_grant_ref. If a
    *     host mapping is destroyed by other means then it is *NOT* guaranteed
    *     to be accounted to the correct grant reference!
    */
   #define GNTTABOP_map_grant_ref        0
   struct gnttab_map_grant_ref {
       /* IN parameters. */
       uint64_t host_addr;
       uint32_t flags;               /* GNTMAP_* */
       grant_ref_t ref;
       domid_t  dom;
       /* OUT parameters. */
       int16_t  status;              /* GNTST_* */
       grant_handle_t handle;
       uint64_t dev_bus_addr;
   };
   typedef struct gnttab_map_grant_ref gnttab_map_grant_ref_t;
   DEFINE_XEN_GUEST_HANDLE(gnttab_map_grant_ref_t);
   
   /*
    * GNTTABOP_unmap_grant_ref: Destroy one or more grant-reference mappings
    * tracked by <handle>. If <host_addr> or <dev_bus_addr> is zero, that
    * field is ignored. If non-zero, they must refer to a device/host mapping
    * that is tracked by <handle>
    * NOTES:
    *  1. The call may fail in an undefined manner if either mapping is not
    *     tracked by <handle>.
    *  3. After executing a batch of unmaps, it is guaranteed that no stale
    *     mappings will remain in the device or host TLBs.
    */
   #define GNTTABOP_unmap_grant_ref      1
   struct gnttab_unmap_grant_ref {
       /* IN parameters. */
       uint64_t host_addr;
       uint64_t dev_bus_addr;
       grant_handle_t handle;
       /* OUT parameters. */
       int16_t  status;              /* GNTST_* */
   };
   typedef struct gnttab_unmap_grant_ref gnttab_unmap_grant_ref_t;
   DEFINE_XEN_GUEST_HANDLE(gnttab_unmap_grant_ref_t);
   
   /*
    * GNTTABOP_setup_table: Set up a grant table for <dom> comprising at least
    * <nr_frames> pages. The frame addresses are written to the <frame_list>.
    * Only <nr_frames> addresses are written, even if the table is larger.
    * NOTES:
    *  1. <dom> may be specified as DOMID_SELF.
    *  2. Only a sufficiently-privileged domain may specify <dom> != DOMID_SELF.
    *  3. Xen may not support more than a single grant-table page per domain.
    */
   #define GNTTABOP_setup_table          2
   struct gnttab_setup_table {
       /* IN parameters. */
       domid_t  dom;
       uint32_t nr_frames;
       /* OUT parameters. */
       int16_t  status;              /* GNTST_* */
       XEN_GUEST_HANDLE(ulong) frame_list;
   };
   typedef struct gnttab_setup_table gnttab_setup_table_t;
   DEFINE_XEN_GUEST_HANDLE(gnttab_setup_table_t);
   
   /*
    * GNTTABOP_dump_table: Dump the contents of the grant table to the
    * xen console. Debugging use only.
    */
   #define GNTTABOP_dump_table           3
   struct gnttab_dump_table {
       /* IN parameters. */
       domid_t dom;
       /* OUT parameters. */
       int16_t status;               /* GNTST_* */
   };
   typedef struct gnttab_dump_table gnttab_dump_table_t;
   DEFINE_XEN_GUEST_HANDLE(gnttab_dump_table_t);
   
   /*
    * GNTTABOP_transfer_grant_ref: Transfer <frame> to a foreign domain. The
    * foreign domain has previously registered its interest in the transfer via
    * <domid, ref>.
    * 
    * Note that, even if the transfer fails, the specified page no longer belongs
    * to the calling domain *unless* the error is GNTST_bad_page.
    */
   #define GNTTABOP_transfer                4
   struct gnttab_transfer {
       /* IN parameters. */
       xen_pfn_t     mfn;
       domid_t       domid;
       grant_ref_t   ref;
       /* OUT parameters. */
       int16_t       status;
   };
   typedef struct gnttab_transfer gnttab_transfer_t;
   DEFINE_XEN_GUEST_HANDLE(gnttab_transfer_t);
   
   
   /*
    * GNTTABOP_copy: Hypervisor based copy
    * source and destinations can be eithers MFNs or, for foreign domains,
    * grant references. the foreign domain has to grant read/write access
    * in its grant table.
    *
    * The flags specify what type source and destinations are (either MFN
    * or grant reference).
    *
    * Note that this can also be used to copy data between two domains
    * via a third party if the source and destination domains had previously
    * grant appropriate access to their pages to the third party.
    *
    * source_offset specifies an offset in the source frame, dest_offset
    * the offset in the target frame and  len specifies the number of
    * bytes to be copied.
    */
   
   #define _GNTCOPY_source_gref      (0)
   #define GNTCOPY_source_gref       (1<<_GNTCOPY_source_gref)
   #define _GNTCOPY_dest_gref        (1)
   #define GNTCOPY_dest_gref         (1<<_GNTCOPY_dest_gref)
   
   #define GNTTABOP_copy                 5
   typedef struct gnttab_copy {
       /* IN parameters. */
       struct {
           union {
               grant_ref_t ref;
               xen_pfn_t   gmfn;
           } u;
           domid_t  domid;
           uint16_t offset;
       } source, dest;
       uint16_t      len;
       uint16_t      flags;          /* GNTCOPY_* */
       /* OUT parameters. */
       int16_t       status;
   } gnttab_copy_t;
   DEFINE_XEN_GUEST_HANDLE(gnttab_copy_t);
   
   /*
    * GNTTABOP_query_size: Query the current and maximum sizes of the shared
    * grant table.
    * NOTES:
    *  1. <dom> may be specified as DOMID_SELF.
    *  2. Only a sufficiently-privileged domain may specify <dom> != DOMID_SELF.
    */
   #define GNTTABOP_query_size           6
   struct gnttab_query_size {
       /* IN parameters. */
       domid_t  dom;
       /* OUT parameters. */
       uint32_t nr_frames;
       uint32_t max_nr_frames;
       int16_t  status;              /* GNTST_* */
   };
   typedef struct gnttab_query_size gnttab_query_size_t;
   DEFINE_XEN_GUEST_HANDLE(gnttab_query_size_t);
   
   /*
    * GNTTABOP_unmap_and_replace: Destroy one or more grant-reference mappings
    * tracked by <handle> but atomically replace the page table entry with one
    * pointing to the machine address under <new_addr>.  <new_addr> will be
    * redirected to the null entry.
    * NOTES:
    *  1. The call may fail in an undefined manner if either mapping is not
    *     tracked by <handle>.
    *  2. After executing a batch of unmaps, it is guaranteed that no stale
    *     mappings will remain in the device or host TLBs.
    */
   #define GNTTABOP_unmap_and_replace    7
   struct gnttab_unmap_and_replace {
       /* IN parameters. */
       uint64_t host_addr;
       uint64_t new_addr;
       grant_handle_t handle;
       /* OUT parameters. */
       int16_t  status;              /* GNTST_* */
   };
   typedef struct gnttab_unmap_and_replace gnttab_unmap_and_replace_t;
   DEFINE_XEN_GUEST_HANDLE(gnttab_unmap_and_replace_t);
   
   
   /*
    * Bitfield values for update_pin_status.flags.
    */
    /* Map the grant entry for access by I/O devices. */
   #define _GNTMAP_device_map      (0)
   #define GNTMAP_device_map       (1<<_GNTMAP_device_map)
    /* Map the grant entry for access by host CPUs. */
   #define _GNTMAP_host_map        (1)
   #define GNTMAP_host_map         (1<<_GNTMAP_host_map)
    /* Accesses to the granted frame will be restricted to read-only access. */
   #define _GNTMAP_readonly        (2)
   #define GNTMAP_readonly         (1<<_GNTMAP_readonly)
    /*
     * GNTMAP_host_map subflag:
     *  0 => The host mapping is usable only by the guest OS.
     *  1 => The host mapping is usable by guest OS + current application.
     */
   #define _GNTMAP_application_map (3)
   #define GNTMAP_application_map  (1<<_GNTMAP_application_map)
   
    /*
     * GNTMAP_contains_pte subflag:
     *  0 => This map request contains a host virtual address.
     *  1 => This map request contains the machine addess of the PTE to update.
     */
   #define _GNTMAP_contains_pte    (4)
   #define GNTMAP_contains_pte     (1<<_GNTMAP_contains_pte)
   
   /*
    * Values for error status returns. All errors are -ve.
    */
   #define GNTST_okay             (0)  /* Normal return.                        */
   #define GNTST_general_error    (-1) /* General undefined error.              */
   #define GNTST_bad_domain       (-2) /* Unrecognsed domain id.                */
   #define GNTST_bad_gntref       (-3) /* Unrecognised or inappropriate gntref. */
   #define GNTST_bad_handle       (-4) /* Unrecognised or inappropriate handle. */
   #define GNTST_bad_virt_addr    (-5) /* Inappropriate virtual address to map. */
   #define GNTST_bad_dev_addr     (-6) /* Inappropriate device address to unmap.*/
   #define GNTST_no_device_space  (-7) /* Out of space in I/O MMU.              */
   #define GNTST_permission_denied (-8) /* Not enough privilege for operation.  */
   #define GNTST_bad_page         (-9) /* Specified page was invalid for op.    */
   #define GNTST_bad_copy_arg    (-10) /* copy arguments cross page boundary.   */
   #define GNTST_address_too_big (-11) /* transfer page address too large.      */
   
   #define GNTTABOP_error_msgs {                   \
       "okay",                                     \
       "undefined error",                          \
       "unrecognised domain id",                   \
       "invalid grant reference",                  \
       "invalid mapping handle",                   \
       "invalid virtual address",                  \
       "invalid device address",                   \
       "no spare translation slot in the I/O MMU", \
       "permission denied",                        \
       "bad page",                                 \
       "copy arguments cross page boundary",       \
       "page address size too large"               \
   }
   
   #endif /* __XEN_PUBLIC_GRANT_TABLE_H__ */
   
   /*
    * Local variables:
    * mode: C
    * c-set-style: "BSD"
    * c-basic-offset: 4
    * tab-width: 4
    * indent-tabs-mode: nil
    * End:
    */

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