LXR linux/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 */
  39enum 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 */
  60static 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 */
  79static 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 */
  96struct 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 */
 110int 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 potentially 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 */
 122