hmm.h

  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
 14struct 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 * HMM_PFN_P2PDMA - P2P page
 27 * HMM_PFN_P2PDMA_BUS - Bus mapped P2P transfer
 28 * HMM_PFN_DMA_MAPPED - Flag preserved on input-to-output transformation
 29 *                      to mark that page is already DMA mapped
 30 *
 31 * On input:
 32 * 0                 - Return the current state of the page, do not fault it.
 33 * HMM_PFN_REQ_FAULT - The output must have HMM_PFN_VALID or hmm_range_fault()
 34 *                     will fail
 35 * HMM_PFN_REQ_WRITE - The output must have HMM_PFN_WRITE or hmm_range_fault()
 36 *                     will fail. Must be combined with HMM_PFN_REQ_FAULT.
 37 */
 38enum hmm_pfn_flags {
 39	/* Output fields and flags */
 40	HMM_PFN_VALID = 1UL << (BITS_PER_LONG - 1),
 41	HMM_PFN_WRITE = 1UL << (BITS_PER_LONG - 2),
 42	HMM_PFN_ERROR = 1UL << (BITS_PER_LONG - 3),
 43	/*
 44	 * Sticky flags, carried from input to output,
 45	 * don't forget to update HMM_PFN_INOUT_FLAGS
 46	 */
 47	HMM_PFN_DMA_MAPPED = 1UL << (BITS_PER_LONG - 4),
 48	HMM_PFN_P2PDMA     = 1UL << (BITS_PER_LONG - 5),
 49	HMM_PFN_P2PDMA_BUS = 1UL << (BITS_PER_LONG - 6),
 50
 51	HMM_PFN_ORDER_SHIFT = (BITS_PER_LONG - 11),
 52
 53	/* Input flags */
 54	HMM_PFN_REQ_FAULT = HMM_PFN_VALID,
 55	HMM_PFN_REQ_WRITE = HMM_PFN_WRITE,
 56
 57	HMM_PFN_FLAGS = ~((1UL << HMM_PFN_ORDER_SHIFT) - 1),
 58};
 59
 60/*
 61 * hmm_pfn_to_page() - return struct page pointed to by a device entry
 62 *
 63 * This must be called under the caller 'user_lock' after a successful
 64 * mmu_interval_read_begin(). The caller must have tested for HMM_PFN_VALID
 65 * already.
 66 */
 67static inline struct page *hmm_pfn_to_page(unsigned long hmm_pfn)
 68{
 69	return pfn_to_page(hmm_pfn & ~HMM_PFN_FLAGS);
 70}
 71
 72/*
 73 * hmm_pfn_to_phys() - return physical address pointed to by a device entry
 74 */
 75static inline phys_addr_t hmm_pfn_to_phys(unsigned long hmm_pfn)
 76{
 77	return __pfn_to_phys(hmm_pfn & ~HMM_PFN_FLAGS);
 78}
 79
 80/*
 81 * hmm_pfn_to_map_order() - return the CPU mapping size order
 82 *
 83 * This is optionally useful to optimize processing of the pfn result
 84 * array. It indicates that the page starts at the order aligned VA and is
 85 * 1<<order bytes long.  Every pfn within an high order page will have the
 86 * same pfn flags, both access protections and the map_order.  The caller must
 87 * be careful with edge cases as the start and end VA of the given page may
 88 * extend past the range used with hmm_range_fault().
 89 *
 90 * This must be called under the caller 'user_lock' after a successful
 91 * mmu_interval_read_begin(). The caller must have tested for HMM_PFN_VALID
 92 * already.
 93 */
 94static inline unsigned int hmm_pfn_to_map_order(unsigned long hmm_pfn)
 95{
 96	return (hmm_pfn >> HMM_PFN_ORDER_SHIFT) & 0x1F;
 97}
 98
 99/*
100 * struct hmm_range - track invalidation lock on virtual address range
101 *
102 * @notifier: a mmu_interval_notifier that includes the start/end
103 * @notifier_seq: result of mmu_interval_read_begin()
104 * @start: range virtual start address (inclusive)
105 * @end: range virtual end address (exclusive)
106 * @hmm_pfns: array of pfns (big enough for the range)
107 * @default_flags: default flags for the range (write, read, ... see hmm doc)
108 * @pfn_flags_mask: allows to mask pfn flags so that only default_flags matter
109 * @dev_private_owner: owner of device private pages
110 */
111struct hmm_range {
112	struct mmu_interval_notifier *notifier;
113	unsigned long		notifier_seq;
114	unsigned long		start;
115	unsigned long		end;
116	unsigned long		*hmm_pfns;
117	unsigned long		default_flags;
118	unsigned long		pfn_flags_mask;
119	void			*dev_private_owner;
120};
121
122/*
123 * Please see Documentation/mm/hmm.rst for how to use the range API.
124 */
125int hmm_range_fault(struct hmm_range *range);
126
127/*
128 * HMM_RANGE_DEFAULT_TIMEOUT - default timeout (ms) when waiting for a range
129 *
130 * When waiting for mmu notifiers we need some kind of time out otherwise we
131 * could potentially wait for ever, 1000ms ie 1s sounds like a long time to
132 * wait already.
133 */
134#define HMM_RANGE_DEFAULT_TIMEOUT 1000
135
136#endif /* LINUX_HMM_H */