xref: /illumos-gate/usr/src/uts/common/sys/hold_page.h (revision 2d6eb4a5e0a47d30189497241345dc5466bb68ab)
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 #ifdef __cplusplus
30 extern "C" {
31 #endif
32 
33 #include <sys/types.h>
34 #include <vm/page.h>
35 
36 /*
37  * swrand generates entropy by mapping different pages in the system.  This
38  * can create problems for some hypervisors, as certain pages may be removed
39  * from the system at any time.  The following interfaces allow swrand to
40  * check the validity and make sure a page is not given away while it is mapped.
41  *
42  * int plat_hold_page(pfn_t pfn, int lock, page_t **pp_ret)
43  *
44  *	If lock is PLAT_HOLD_NO_LOCK, simply check if the page pfn is valid
45  *	in the system.  If the page is valid, PLAT_HOLD_OK will be returned.
46  *	pp_ret is ignored if lock is PLAT_HOLD_NO_LOCK.
47  *
48  *	If lock is PLAT_HOLD_LOCK, in addition to the above, attempt to lock
49  *	the page exclusively.  Again, if the lock is successful, the page
50  *	pointer will be put in pp_ret, and PLAT_HOLD_OK will be returned.
51  *	pp_ret must be passed to a later call to plat_release_page.  If the
52  *	page wasn't found, or the lock couldn't be grabbed, the return value
53  *	will be PLAT_HOLD_FAIL.
54  *
55  * void plat_release_page(page_t *pp)
56  *
57  *	Unlock the page pp.  Should only be called after a previous,
58  *	successful call to plat_hold_page(pfn, PLAT_HOLD_LOCK, &pp);
59  */
60 
61 #define	PLAT_HOLD_NO_LOCK	0
62 #define	PLAT_HOLD_LOCK		1
63 
64 #define	PLAT_HOLD_OK		0
65 #define	PLAT_HOLD_FAIL		1
66 
67 extern int plat_hold_page(pfn_t, int, page_t **);
68 extern void plat_release_page(page_t *);
69 
70 #ifdef __cplusplus
71 }
72 #endif
73 
74 #endif	/* _SYS_HOLD_PAGE_H */
75