usr/src/uts/common/sys/hold_page.h

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21 /*
  22  * Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
  23  * Use is subject to license terms.
  24  */
  25
  26 #ifndef _SYS_HOLD_PAGE_H
  27 #define _SYS_HOLD_PAGE_H
  28
  29 #pragma ident   "%Z%%M% %I%     %E% SMI"
  30
  31 #ifdef __cplusplus
  32 extern "C" {
  33 #endif
  34
  35 #include <sys/types.h>
  36 #include <vm/page.h>
  37
  38 /*
  39  * swrand generates entropy by mapping different pages in the system.  This
  40  * can create problems for some hypervisors, as certain pages may be removed
  41  * from the system at any time.  The following interfaces allow swrand to
  42  * check the validity and make sure a page is not given away while it is mapped.
  43  *
  44  * int plat_hold_page(pfn_t pfn, int lock, page_t **pp_ret)
  45  *
  46  *      If lock is PLAT_HOLD_NO_LOCK, simply check if the page pfn is valid
  47  *      in the system.  If the page is valid, PLAT_HOLD_OK will be returned.
  48  *      pp_ret is ignored if lock is PLAT_HOLD_NO_LOCK.
  49  *
  50  *      If lock is PLAT_HOLD_LOCK, in addition to the above, attempt to lock
  51  *      the page exclusively.  Again, if the lock is successful, the page
  52  *      pointer will be put in pp_ret, and PLAT_HOLD_OK will be returned.
  53  *      pp_ret must be passed to a later call to plat_release_page.  If the
  54  *      page wasn't found, or the lock couldn't be grabbed, the return value
  55  *      will be PLAT_HOLD_FAIL.
  56  *
  57  * void plat_release_page(page_t *pp)
  58  *
  59  *      Unlock the page pp.  Should only be called after a previous,
  60  *      successful call to plat_hold_page(pfn, PLAT_HOLD_LOCK, &pp);
  61  */
  62
  63 #define PLAT_HOLD_NO_LOCK       0
  64 #define PLAT_HOLD_LOCK          1
  65
  66 #define PLAT_HOLD_OK            0
  67 #define PLAT_HOLD_FAIL          1
  68
  69 extern int plat_hold_page(pfn_t, int, page_t **);
  70 extern void plat_release_page(page_t *);
  71
  72 #ifdef __cplusplus
  73 }
  74 #endif
  75
  76 #endif  /* _SYS_HOLD_PAGE_H */