include/linux/hmm.h

0001 /* SPDX-License-Identifier: GPL-2.0-or-later */
0002 /*
0003  * Copyright 2013 Red Hat Inc.
0004  *
0005  * Authors: Jérôme Glisse <jglisse@redhat.com>
0006  *
0007  * See Documentation/mm/hmm.rst for reasons and overview of what HMM is.
0008  */
0009 #ifndef LINUX_HMM_H
0010 #define LINUX_HMM_H
0011
0012 #include <linux/mm.h>
0013
0014 struct mmu_interval_notifier;
0015
0016 /*
0017  * On output:
0018  * 0             - The page is faultable and a future call with
0019  *                 HMM_PFN_REQ_FAULT could succeed.
0020  * HMM_PFN_VALID - the pfn field points to a valid PFN. This PFN is at
0021  *                 least readable. If dev_private_owner is !NULL then this could
0022  *                 point at a DEVICE_PRIVATE page.
0023  * HMM_PFN_WRITE - if the page memory can be written to (requires HMM_PFN_VALID)
0024  * HMM_PFN_ERROR - accessing the pfn is impossible and the device should
0025  *                 fail. ie poisoned memory, special pages, no vma, etc
0026  *
0027  * On input:
0028  * 0                 - Return the current state of the page, do not fault it.
0029  * HMM_PFN_REQ_FAULT - The output must have HMM_PFN_VALID or hmm_range_fault()
0030  *                     will fail
0031  * HMM_PFN_REQ_WRITE - The output must have HMM_PFN_WRITE or hmm_range_fault()
0032  *                     will fail. Must be combined with HMM_PFN_REQ_FAULT.
0033  */
0034 enum hmm_pfn_flags {
0035     /* Output fields and flags */
0036     HMM_PFN_VALID = 1UL << (BITS_PER_LONG - 1),
0037     HMM_PFN_WRITE = 1UL << (BITS_PER_LONG - 2),
0038     HMM_PFN_ERROR = 1UL << (BITS_PER_LONG - 3),
0039     HMM_PFN_ORDER_SHIFT = (BITS_PER_LONG - 8),
0040
0041     /* Input flags */
0042     HMM_PFN_REQ_FAULT = HMM_PFN_VALID,
0043     HMM_PFN_REQ_WRITE = HMM_PFN_WRITE,
0044
0045     HMM_PFN_FLAGS = 0xFFUL << HMM_PFN_ORDER_SHIFT,
0046 };
0047
0048 /*
0049  * hmm_pfn_to_page() - return struct page pointed to by a device entry
0050  *
0051  * This must be called under the caller 'user_lock' after a successful
0052  * mmu_interval_read_begin(). The caller must have tested for HMM_PFN_VALID
0053  * already.
0054  */
0055 static inline struct page *hmm_pfn_to_page(unsigned long hmm_pfn)
0056 {
0057     return pfn_to_page(hmm_pfn & ~HMM_PFN_FLAGS);
0058 }
0059
0060 /*
0061  * hmm_pfn_to_map_order() - return the CPU mapping size order
0062  *
0063  * This is optionally useful to optimize processing of the pfn result
0064  * array. It indicates that the page starts at the order aligned VA and is
0065  * 1<<order bytes long.  Every pfn within an high order page will have the
0066  * same pfn flags, both access protections and the map_order.  The caller must
0067  * be careful with edge cases as the start and end VA of the given page may
0068  * extend past the range used with hmm_range_fault().
0069  *
0070  * This must be called under the caller 'user_lock' after a successful
0071  * mmu_interval_read_begin(). The caller must have tested for HMM_PFN_VALID
0072  * already.
0073  */
0074 static inline unsigned int hmm_pfn_to_map_order(unsigned long hmm_pfn)
0075 {
0076     return (hmm_pfn >> HMM_PFN_ORDER_SHIFT) & 0x1F;
0077 }
0078
0079 /*
0080  * struct hmm_range - track invalidation lock on virtual address range
0081  *
0082  * @notifier: a mmu_interval_notifier that includes the start/end
0083  * @notifier_seq: result of mmu_interval_read_begin()
0084  * @start: range virtual start address (inclusive)
0085  * @end: range virtual end address (exclusive)
0086  * @hmm_pfns: array of pfns (big enough for the range)
0087  * @default_flags: default flags for the range (write, read, ... see hmm doc)
0088  * @pfn_flags_mask: allows to mask pfn flags so that only default_flags matter
0089  * @dev_private_owner: owner of device private pages
0090  */
0091 struct hmm_range {
0092     struct mmu_interval_notifier *notifier;
0093     unsigned long       notifier_seq;
0094     unsigned long       start;
0095     unsigned long       end;
0096     unsigned long       *hmm_pfns;
0097     unsigned long       default_flags;
0098     unsigned long       pfn_flags_mask;
0099     void            *dev_private_owner;
0100 };
0101
0102 /*
0103  * Please see Documentation/mm/hmm.rst for how to use the range API.
0104  */
0105 int hmm_range_fault(struct hmm_range *range);
0106
0107 /*
0108  * HMM_RANGE_DEFAULT_TIMEOUT - default timeout (ms) when waiting for a range
0109  *
0110  * When waiting for mmu notifiers we need some kind of time out otherwise we
0111  * could potentially wait for ever, 1000ms ie 1s sounds like a long time to
0112  * wait already.
0113  */
0114 #define HMM_RANGE_DEFAULT_TIMEOUT 1000
0115
0116 #endif /* LINUX_HMM_H */