1 /* SPDX-License-Identifier: GPL-2.0-or-later */
2 /*
3  * Copyright 2013 Red Hat Inc.
4  *
5  * Authors: Jérôme Glisse <jglisse@redhat.com>
6  *
7  * See Documentation/mm/hmm.rst for reasons and overview of what HMM is.
8  */
9 #ifndef LINUX_HMM_H
10 #define LINUX_HMM_H
11 
12 #include <linux/mm.h>
13 
14 struct mmu_interval_notifier;
15 
16 /*
17  * On output:
18  * 0             - The page is faultable and a future call with
19  *                 HMM_PFN_REQ_FAULT could succeed.
20  * HMM_PFN_VALID - the pfn field points to a valid PFN. This PFN is at
21  *                 least readable. If dev_private_owner is !NULL then this could
22  *                 point at a DEVICE_PRIVATE page.
23  * HMM_PFN_WRITE - if the page memory can be written to (requires HMM_PFN_VALID)
24  * HMM_PFN_ERROR - accessing the pfn is impossible and the device should
25  *                 fail. ie poisoned memory, special pages, no vma, etc
26  *
27  * On input:
28  * 0                 - Return the current state of the page, do not fault it.
29  * HMM_PFN_REQ_FAULT - The output must have HMM_PFN_VALID or hmm_range_fault()
30  *                     will fail
31  * HMM_PFN_REQ_WRITE - The output must have HMM_PFN_WRITE or hmm_range_fault()
32  *                     will fail. Must be combined with HMM_PFN_REQ_FAULT.
33  */
34 enum hmm_pfn_flags {
35 	/* Output fields and flags */
36 	HMM_PFN_VALID = 1UL << (BITS_PER_LONG - 1),
37 	HMM_PFN_WRITE = 1UL << (BITS_PER_LONG - 2),
38 	HMM_PFN_ERROR = 1UL << (BITS_PER_LONG - 3),
39 	HMM_PFN_ORDER_SHIFT = (BITS_PER_LONG - 8),
40 
41 	/* Input flags */
42 	HMM_PFN_REQ_FAULT = HMM_PFN_VALID,
43 	HMM_PFN_REQ_WRITE = HMM_PFN_WRITE,
44 
45 	HMM_PFN_FLAGS = 0xFFUL << HMM_PFN_ORDER_SHIFT,
46 };
47 
48 /*
49  * hmm_pfn_to_page() - return struct page pointed to by a device entry
50  *
51  * This must be called under the caller 'user_lock' after a successful
52  * mmu_interval_read_begin(). The caller must have tested for HMM_PFN_VALID
53  * already.
54  */
hmm_pfn_to_page(unsigned long hmm_pfn)55 static inline struct page *hmm_pfn_to_page(unsigned long hmm_pfn)
56 {
57 	return pfn_to_page(hmm_pfn & ~HMM_PFN_FLAGS);
58 }
59 
60 /*
61  * hmm_pfn_to_map_order() - return the CPU mapping size order
62  *
63  * This is optionally useful to optimize processing of the pfn result
64  * array. It indicates that the page starts at the order aligned VA and is
65  * 1<<order bytes long.  Every pfn within an high order page will have the
66  * same pfn flags, both access protections and the map_order.  The caller must
67  * be careful with edge cases as the start and end VA of the given page may
68  * extend past the range used with hmm_range_fault().
69  *
70  * This must be called under the caller 'user_lock' after a successful
71  * mmu_interval_read_begin(). The caller must have tested for HMM_PFN_VALID
72  * already.
73  */
hmm_pfn_to_map_order(unsigned long hmm_pfn)74 static inline unsigned int hmm_pfn_to_map_order(unsigned long hmm_pfn)
75 {
76 	return (hmm_pfn >> HMM_PFN_ORDER_SHIFT) & 0x1F;
77 }
78 
79 /*
80  * struct hmm_range - track invalidation lock on virtual address range
81  *
82  * @notifier: a mmu_interval_notifier that includes the start/end
83  * @notifier_seq: result of mmu_interval_read_begin()
84  * @start: range virtual start address (inclusive)
85  * @end: range virtual end address (exclusive)
86  * @hmm_pfns: array of pfns (big enough for the range)
87  * @default_flags: default flags for the range (write, read, ... see hmm doc)
88  * @pfn_flags_mask: allows to mask pfn flags so that only default_flags matter
89  * @dev_private_owner: owner of device private pages
90  */
91 struct hmm_range {
92 	struct mmu_interval_notifier *notifier;
93 	unsigned long		notifier_seq;
94 	unsigned long		start;
95 	unsigned long		end;
96 	unsigned long		*hmm_pfns;
97 	unsigned long		default_flags;
98 	unsigned long		pfn_flags_mask;
99 	void			*dev_private_owner;
100 };
101 
102 /*
103  * Please see Documentation/mm/hmm.rst for how to use the range API.
104  */
105 int hmm_range_fault(struct hmm_range *range);
106 
107 /*
108  * HMM_RANGE_DEFAULT_TIMEOUT - default timeout (ms) when waiting for a range
109  *
110  * When waiting for mmu notifiers we need some kind of time out otherwise we
111  * could potentially wait for ever, 1000ms ie 1s sounds like a long time to
112  * wait already.
113  */
114 #define HMM_RANGE_DEFAULT_TIMEOUT 1000
115 
116 #endif /* LINUX_HMM_H */
117