usr/src/uts/i86pc/os/hold_page.c

   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 /*
  23  * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
  24  * Use is subject to license terms.
  25  */
  26
  27 #include <sys/hold_page.h>
  28
  29 #if defined(__xpv)
  30 #include <sys/hypervisor.h>
  31 #endif
  32
  33 int
  34 plat_hold_page(pfn_t pfn, int lock, page_t **pp_ret)
  35 {
  36         page_t *pp = page_numtopp_nolock(pfn);
  37
  38         if (pp == NULL)
  39                 return (PLAT_HOLD_FAIL);
  40
  41 #if !defined(__xpv)
  42         /*
  43          * Pages are locked SE_SHARED because some hypervisors
  44          * like xVM ESX reclaim Guest OS memory by locking
  45          * it SE_EXCL so we want to leave these pages alone.
  46          */
  47         if (lock == PLAT_HOLD_LOCK) {
  48                 ASSERT(pp_ret != NULL);
  49                 if (page_trylock(pp, SE_SHARED) == 0)
  50                         return (PLAT_HOLD_FAIL);
  51         }
  52 #else   /* __xpv */
  53         if (lock == PLAT_HOLD_LOCK) {
  54                 ASSERT(pp_ret != NULL);
  55                 if (page_trylock(pp, SE_EXCL) == 0)
  56                         return (PLAT_HOLD_FAIL);
  57         }
  58
  59         if (mfn_list[pfn] == MFN_INVALID) {
  60                 /* We failed - release the lock if we grabbed it earlier */
  61                 if (lock == PLAT_HOLD_LOCK) {
  62                         page_unlock(pp);
  63                 }
  64                 return (PLAT_HOLD_FAIL);
  65         }
  66 #endif  /* __xpv */
  67
  68         if (lock == PLAT_HOLD_LOCK)
  69                 *pp_ret = pp;
  70
  71         return (PLAT_HOLD_OK);
  72 }
  73
  74 void
  75 plat_release_page(page_t *pp)
  76 {
  77         ASSERT((pp != NULL) && PAGE_LOCKED(pp));
  78         page_unlock(pp);
  79 }