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
32extern "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
69extern int plat_hold_page(pfn_t, int, page_t **);
70extern void plat_release_page(page_t *);
71
72#ifdef __cplusplus
73}
74#endif
75
76#endif	/* _SYS_HOLD_PAGE_H */
77