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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/vm/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/kconfig.h>
13#include <asm/pgtable.h>
14
15#include <linux/device.h>
16#include <linux/migrate.h>
17#include <linux/memremap.h>
18#include <linux/completion.h>
19#include <linux/mmu_notifier.h>
20
21/*
22 * hmm_pfn_flag_e - HMM flag enums
23 *
24 * Flags:
25 * HMM_PFN_VALID: pfn is valid. It has, at least, read permission.
26 * HMM_PFN_WRITE: CPU page table has write permission set
27 *
28 * The driver provides a flags array for mapping page protections to device
29 * PTE bits. If the driver valid bit for an entry is bit 3,
30 * i.e., (entry & (1 << 3)), then the driver must provide
31 * an array in hmm_range.flags with hmm_range.flags[HMM_PFN_VALID] == 1 << 3.
32 * Same logic apply to all flags. This is the same idea as vm_page_prot in vma
33 * except that this is per device driver rather than per architecture.
34 */
35enum hmm_pfn_flag_e {
36 HMM_PFN_VALID = 0,
37 HMM_PFN_WRITE,
38 HMM_PFN_FLAG_MAX
39};
40
41/*
42 * hmm_pfn_value_e - HMM pfn special value
43 *
44 * Flags:
45 * HMM_PFN_ERROR: corresponding CPU page table entry points to poisoned memory
46 * HMM_PFN_NONE: corresponding CPU page table entry is pte_none()
47 * HMM_PFN_SPECIAL: corresponding CPU page table entry is special; i.e., the
48 * result of vmf_insert_pfn() or vm_insert_page(). Therefore, it should not
49 * be mirrored by a device, because the entry will never have HMM_PFN_VALID
50 * set and the pfn value is undefined.
51 *
52 * Driver provides values for none entry, error entry, and special entry.
53 * Driver can alias (i.e., use same value) error and special, but
54 * it should not alias none with error or special.
55 *
56 * HMM pfn value returned by hmm_vma_get_pfns() or hmm_vma_fault() will be:
57 * hmm_range.values[HMM_PFN_ERROR] if CPU page table entry is poisonous,
58 * hmm_range.values[HMM_PFN_NONE] if there is no CPU page table entry,
59 * hmm_range.values[HMM_PFN_SPECIAL] if CPU page table entry is a special one
60 */
61enum hmm_pfn_value_e {
62 HMM_PFN_ERROR,
63 HMM_PFN_NONE,
64 HMM_PFN_SPECIAL,
65 HMM_PFN_VALUE_MAX
66};
67
68/*
69 * struct hmm_range - track invalidation lock on virtual address range
70 *
71 * @notifier: a mmu_interval_notifier that includes the start/end
72 * @notifier_seq: result of mmu_interval_read_begin()
73 * @start: range virtual start address (inclusive)
74 * @end: range virtual end address (exclusive)
75 * @pfns: array of pfns (big enough for the range)
76 * @flags: pfn flags to match device driver page table
77 * @values: pfn value for some special case (none, special, error, ...)
78 * @default_flags: default flags for the range (write, read, ... see hmm doc)
79 * @pfn_flags_mask: allows to mask pfn flags so that only default_flags matter
80 * @pfn_shift: pfn shift value (should be <= PAGE_SHIFT)
81 * @dev_private_owner: owner of device private pages
82 */
83struct hmm_range {
84 struct mmu_interval_notifier *notifier;
85 unsigned long notifier_seq;
86 unsigned long start;
87 unsigned long end;
88 uint64_t *pfns;
89 const uint64_t *flags;
90 const uint64_t *values;
91 uint64_t default_flags;
92 uint64_t pfn_flags_mask;
93 uint8_t pfn_shift;
94 void *dev_private_owner;
95};
96
97/*
98 * hmm_device_entry_to_page() - return struct page pointed to by a device entry
99 * @range: range use to decode device entry value
100 * @entry: device entry value to get corresponding struct page from
101 * Return: struct page pointer if entry is a valid, NULL otherwise
102 *
103 * If the device entry is valid (ie valid flag set) then return the struct page
104 * matching the entry value. Otherwise return NULL.
105 */
106static inline struct page *hmm_device_entry_to_page(const struct hmm_range *range,
107 uint64_t entry)
108{
109 if (entry == range->values[HMM_PFN_NONE])
110 return NULL;
111 if (entry == range->values[HMM_PFN_ERROR])
112 return NULL;
113 if (entry == range->values[HMM_PFN_SPECIAL])
114 return NULL;
115 if (!(entry & range->flags[HMM_PFN_VALID]))
116 return NULL;
117 return pfn_to_page(entry >> range->pfn_shift);
118}
119
120/*
121 * Please see Documentation/vm/hmm.rst for how to use the range API.
122 */
123long hmm_range_fault(struct hmm_range *range);
124
125/*
126 * HMM_RANGE_DEFAULT_TIMEOUT - default timeout (ms) when waiting for a range
127 *
128 * When waiting for mmu notifiers we need some kind of time out otherwise we
129 * could potentialy wait for ever, 1000ms ie 1s sounds like a long time to
130 * wait already.
131 */
132#define HMM_RANGE_DEFAULT_TIMEOUT 1000
133
134#endif /* LINUX_HMM_H */