include/linux/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/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 <linux/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  * On output:
  23  * 0             - The page is faultable and a future call with
  24  *                 HMM_PFN_REQ_FAULT could succeed.
  25  * HMM_PFN_VALID - the pfn field points to a valid PFN. This PFN is at
  26  *                 least readable. If dev_private_owner is !NULL then this could
  27  *                 point at a DEVICE_PRIVATE page.
  28  * HMM_PFN_WRITE - if the page memory can be written to (requires HMM_PFN_VALID)
  29  * HMM_PFN_ERROR - accessing the pfn is impossible and the device should
  30  *                 fail. ie poisoned memory, special pages, no vma, etc
  31  *
  32  * On input:
  33  * 0                 - Return the current state of the page, do not fault it.
  34  * HMM_PFN_REQ_FAULT - The output must have HMM_PFN_VALID or hmm_range_fault()
  35  *                     will fail
  36  * HMM_PFN_REQ_WRITE - The output must have HMM_PFN_WRITE or hmm_range_fault()
  37  *                     will fail. Must be combined with HMM_PFN_REQ_FAULT.
  38  */
  39 enum hmm_pfn_flags {
  40         /* Output fields and flags */
  41         HMM_PFN_VALID = 1UL << (BITS_PER_LONG - 1),
  42         HMM_PFN_WRITE = 1UL << (BITS_PER_LONG - 2),
  43         HMM_PFN_ERROR = 1UL << (BITS_PER_LONG - 3),
  44         HMM_PFN_ORDER_SHIFT = (BITS_PER_LONG - 8),
  45
  46         /* Input flags */
  47         HMM_PFN_REQ_FAULT = HMM_PFN_VALID,
  48         HMM_PFN_REQ_WRITE = HMM_PFN_WRITE,
  49
  50         HMM_PFN_FLAGS = 0xFFUL << HMM_PFN_ORDER_SHIFT,
  51 };
  52
  53 /*
  54  * hmm_pfn_to_page() - return struct page pointed to by a device entry
  55  *
  56  * This must be called under the caller 'user_lock' after a successful
  57  * mmu_interval_read_begin(). The caller must have tested for HMM_PFN_VALID
  58  * already.
  59  */
  60 static inline struct page *hmm_pfn_to_page(unsigned long hmm_pfn)
  61 {
  62         return pfn_to_page(hmm_pfn & ~HMM_PFN_FLAGS);
  63 }
  64
  65 /*
  66  * hmm_pfn_to_map_order() - return the CPU mapping size order
  67  *
  68  * This is optionally useful to optimize processing of the pfn result
  69  * array. It indicates that the page starts at the order aligned VA and is
  70  * 1<<order bytes long.  Every pfn within an high order page will have the
  71  * same pfn flags, both access protections and the map_order.  The caller must
  72  * be careful with edge cases as the start and end VA of the given page may
  73  * extend past the range used with hmm_range_fault().
  74  *
  75  * This must be called under the caller 'user_lock' after a successful
  76  * mmu_interval_read_begin(). The caller must have tested for HMM_PFN_VALID
  77  * already.
  78  */
  79 static inline unsigned int hmm_pfn_to_map_order(unsigned long hmm_pfn)
  80 {
  81         return (hmm_pfn >> HMM_PFN_ORDER_SHIFT) & 0x1F;
  82 }
  83
  84 /*
  85  * struct hmm_range - track invalidation lock on virtual address range
  86  *
  87  * @notifier: a mmu_interval_notifier that includes the start/end
  88  * @notifier_seq: result of mmu_interval_read_begin()
  89  * @start: range virtual start address (inclusive)
  90  * @end: range virtual end address (exclusive)
  91  * @hmm_pfns: array of pfns (big enough for the range)
  92  * @default_flags: default flags for the range (write, read, ... see hmm doc)
  93  * @pfn_flags_mask: allows to mask pfn flags so that only default_flags matter
  94  * @dev_private_owner: owner of device private pages
  95  */
  96 struct hmm_range {
  97         struct mmu_interval_notifier *notifier;
  98         unsigned long           notifier_seq;
  99         unsigned long           start;
 100         unsigned long           end;
 101         unsigned long           *hmm_pfns;
 102         unsigned long           default_flags;
 103         unsigned long           pfn_flags_mask;
 104         void                    *dev_private_owner;
 105 };
 106
 107 /*
 108  * Please see Documentation/vm/hmm.rst for how to use the range API.
 109  */
 110 int hmm_range_fault(struct hmm_range *range);
 111
 112 /*
 113  * HMM_RANGE_DEFAULT_TIMEOUT - default timeout (ms) when waiting for a range
 114  *
 115  * When waiting for mmu notifiers we need some kind of time out otherwise we
 116  * could potentialy wait for ever, 1000ms ie 1s sounds like a long time to
 117  * wait already.
 118  */
 119 #define HMM_RANGE_DEFAULT_TIMEOUT 1000
 120
 121 #endif /* LINUX_HMM_H */