/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

/*
 * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#include <sys/hold_page.h>

#if defined(__xpv)
#include <sys/hypervisor.h>
#endif

int
plat_hold_page(pfn_t pfn, int lock, page_t **pp_ret)
{
        page_t *pp = page_numtopp_nolock(pfn);

        if (pp == NULL)
                return (PLAT_HOLD_FAIL);

#if !defined(__xpv)
        /*
         * Pages are locked SE_SHARED because some hypervisors
         * like xVM ESX reclaim Guest OS memory by locking
         * it SE_EXCL so we want to leave these pages alone.
         */
        if (lock == PLAT_HOLD_LOCK) {
                ASSERT(pp_ret != NULL);
                if (page_trylock(pp, SE_SHARED) == 0)
                        return (PLAT_HOLD_FAIL);
        }
#else   /* __xpv */
        if (lock == PLAT_HOLD_LOCK) {
                ASSERT(pp_ret != NULL);
                if (page_trylock(pp, SE_EXCL) == 0)
                        return (PLAT_HOLD_FAIL);
        }

        if (mfn_list[pfn] == MFN_INVALID) {
                /* We failed - release the lock if we grabbed it earlier */
                if (lock == PLAT_HOLD_LOCK) {
                        page_unlock(pp);
                }
                return (PLAT_HOLD_FAIL);
        }
#endif  /* __xpv */

        if (lock == PLAT_HOLD_LOCK)
                *pp_ret = pp;

        return (PLAT_HOLD_OK);
}

void
plat_release_page(page_t *pp)
{
        ASSERT((pp != NULL) && PAGE_LOCKED(pp));
        page_unlock(pp);
}