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![Christoph Hellwig](/assets/img/avatar_default.png)
The code hasn't been used since it was added to the tree, and doesn't appear to actually be usable. Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Jason Gunthorpe <jgg@mellanox.com> Acked-by: Michal Hocko <mhocko@suse.com> Reviewed-by: Dan Williams <dan.j.williams@intel.com> Tested-by: Dan Williams <dan.j.williams@intel.com> Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
757 lines
25 KiB
C
757 lines
25 KiB
C
/* SPDX-License-Identifier: GPL-2.0-or-later */
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/*
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* Copyright 2013 Red Hat Inc.
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*
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* Authors: Jérôme Glisse <jglisse@redhat.com>
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*/
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/*
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* Heterogeneous Memory Management (HMM)
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*
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* See Documentation/vm/hmm.rst for reasons and overview of what HMM is and it
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* is for. Here we focus on the HMM API description, with some explanation of
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* the underlying implementation.
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*
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* Short description: HMM provides a set of helpers to share a virtual address
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* space between CPU and a device, so that the device can access any valid
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* address of the process (while still obeying memory protection). HMM also
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* provides helpers to migrate process memory to device memory, and back. Each
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* set of functionality (address space mirroring, and migration to and from
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* device memory) can be used independently of the other.
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*
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*
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* HMM address space mirroring API:
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*
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* Use HMM address space mirroring if you want to mirror range of the CPU page
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* table of a process into a device page table. Here, "mirror" means "keep
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* synchronized". Prerequisites: the device must provide the ability to write-
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* protect its page tables (at PAGE_SIZE granularity), and must be able to
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* recover from the resulting potential page faults.
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*
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* HMM guarantees that at any point in time, a given virtual address points to
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* either the same memory in both CPU and device page tables (that is: CPU and
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* device page tables each point to the same pages), or that one page table (CPU
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* or device) points to no entry, while the other still points to the old page
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* for the address. The latter case happens when the CPU page table update
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* happens first, and then the update is mirrored over to the device page table.
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* This does not cause any issue, because the CPU page table cannot start
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* pointing to a new page until the device page table is invalidated.
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*
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* HMM uses mmu_notifiers to monitor the CPU page tables, and forwards any
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* updates to each device driver that has registered a mirror. It also provides
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* some API calls to help with taking a snapshot of the CPU page table, and to
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* synchronize with any updates that might happen concurrently.
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*
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*
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* HMM migration to and from device memory:
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*
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* HMM provides a set of helpers to hotplug device memory as ZONE_DEVICE, with
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* a new MEMORY_DEVICE_PRIVATE type. This provides a struct page for each page
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* of the device memory, and allows the device driver to manage its memory
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* using those struct pages. Having struct pages for device memory makes
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* migration easier. Because that memory is not addressable by the CPU it must
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* never be pinned to the device; in other words, any CPU page fault can always
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* cause the device memory to be migrated (copied/moved) back to regular memory.
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*
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* A new migrate helper (migrate_vma()) has been added (see mm/migrate.c) that
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* allows use of a device DMA engine to perform the copy operation between
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* regular system memory and device memory.
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*/
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#ifndef LINUX_HMM_H
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#define LINUX_HMM_H
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#include <linux/kconfig.h>
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#include <asm/pgtable.h>
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#if IS_ENABLED(CONFIG_HMM)
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#include <linux/device.h>
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#include <linux/migrate.h>
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#include <linux/memremap.h>
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#include <linux/completion.h>
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#include <linux/mmu_notifier.h>
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/*
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* struct hmm - HMM per mm struct
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*
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* @mm: mm struct this HMM struct is bound to
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* @lock: lock protecting ranges list
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* @ranges: list of range being snapshotted
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* @mirrors: list of mirrors for this mm
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* @mmu_notifier: mmu notifier to track updates to CPU page table
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* @mirrors_sem: read/write semaphore protecting the mirrors list
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* @wq: wait queue for user waiting on a range invalidation
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* @notifiers: count of active mmu notifiers
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* @dead: is the mm dead ?
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*/
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struct hmm {
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struct mm_struct *mm;
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struct kref kref;
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struct mutex lock;
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struct list_head ranges;
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struct list_head mirrors;
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struct mmu_notifier mmu_notifier;
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struct rw_semaphore mirrors_sem;
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wait_queue_head_t wq;
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long notifiers;
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bool dead;
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};
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/*
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* hmm_pfn_flag_e - HMM flag enums
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*
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* Flags:
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* HMM_PFN_VALID: pfn is valid. It has, at least, read permission.
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* HMM_PFN_WRITE: CPU page table has write permission set
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* HMM_PFN_DEVICE_PRIVATE: private device memory (ZONE_DEVICE)
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*
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* The driver provide a flags array, if driver valid bit for an entry is bit
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* 3 ie (entry & (1 << 3)) is true if entry is valid then driver must provide
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* an array in hmm_range.flags with hmm_range.flags[HMM_PFN_VALID] == 1 << 3.
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* Same logic apply to all flags. This is same idea as vm_page_prot in vma
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* except that this is per device driver rather than per architecture.
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*/
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enum hmm_pfn_flag_e {
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HMM_PFN_VALID = 0,
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HMM_PFN_WRITE,
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HMM_PFN_DEVICE_PRIVATE,
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HMM_PFN_FLAG_MAX
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};
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/*
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* hmm_pfn_value_e - HMM pfn special value
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*
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* Flags:
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* HMM_PFN_ERROR: corresponding CPU page table entry points to poisoned memory
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* HMM_PFN_NONE: corresponding CPU page table entry is pte_none()
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* HMM_PFN_SPECIAL: corresponding CPU page table entry is special; i.e., the
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* result of vmf_insert_pfn() or vm_insert_page(). Therefore, it should not
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* be mirrored by a device, because the entry will never have HMM_PFN_VALID
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* set and the pfn value is undefined.
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*
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* Driver provide entry value for none entry, error entry and special entry,
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* driver can alias (ie use same value for error and special for instance). It
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* should not alias none and error or special.
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*
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* HMM pfn value returned by hmm_vma_get_pfns() or hmm_vma_fault() will be:
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* hmm_range.values[HMM_PFN_ERROR] if CPU page table entry is poisonous,
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* hmm_range.values[HMM_PFN_NONE] if there is no CPU page table
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* hmm_range.values[HMM_PFN_SPECIAL] if CPU page table entry is a special one
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*/
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enum hmm_pfn_value_e {
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HMM_PFN_ERROR,
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HMM_PFN_NONE,
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HMM_PFN_SPECIAL,
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HMM_PFN_VALUE_MAX
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};
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/*
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* struct hmm_range - track invalidation lock on virtual address range
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*
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* @hmm: the core HMM structure this range is active against
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* @vma: the vm area struct for the range
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* @list: all range lock are on a list
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* @start: range virtual start address (inclusive)
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* @end: range virtual end address (exclusive)
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* @pfns: array of pfns (big enough for the range)
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* @flags: pfn flags to match device driver page table
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* @values: pfn value for some special case (none, special, error, ...)
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* @default_flags: default flags for the range (write, read, ... see hmm doc)
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* @pfn_flags_mask: allows to mask pfn flags so that only default_flags matter
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* @pfn_shifts: pfn shift value (should be <= PAGE_SHIFT)
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* @valid: pfns array did not change since it has been fill by an HMM function
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*/
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struct hmm_range {
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struct hmm *hmm;
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struct vm_area_struct *vma;
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struct list_head list;
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unsigned long start;
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unsigned long end;
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uint64_t *pfns;
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const uint64_t *flags;
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const uint64_t *values;
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uint64_t default_flags;
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uint64_t pfn_flags_mask;
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uint8_t page_shift;
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uint8_t pfn_shift;
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bool valid;
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};
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/*
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* hmm_range_page_shift() - return the page shift for the range
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* @range: range being queried
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* Returns: page shift (page size = 1 << page shift) for the range
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*/
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static inline unsigned hmm_range_page_shift(const struct hmm_range *range)
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{
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return range->page_shift;
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}
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/*
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* hmm_range_page_size() - return the page size for the range
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* @range: range being queried
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* Returns: page size for the range in bytes
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*/
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static inline unsigned long hmm_range_page_size(const struct hmm_range *range)
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{
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return 1UL << hmm_range_page_shift(range);
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}
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/*
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* hmm_range_wait_until_valid() - wait for range to be valid
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* @range: range affected by invalidation to wait on
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* @timeout: time out for wait in ms (ie abort wait after that period of time)
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* Returns: true if the range is valid, false otherwise.
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*/
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static inline bool hmm_range_wait_until_valid(struct hmm_range *range,
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unsigned long timeout)
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{
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/* Check if mm is dead ? */
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if (range->hmm == NULL || range->hmm->dead || range->hmm->mm == NULL) {
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range->valid = false;
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return false;
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}
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if (range->valid)
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return true;
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wait_event_timeout(range->hmm->wq, range->valid || range->hmm->dead,
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msecs_to_jiffies(timeout));
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/* Return current valid status just in case we get lucky */
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return range->valid;
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}
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/*
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* hmm_range_valid() - test if a range is valid or not
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* @range: range
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* Returns: true if the range is valid, false otherwise.
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*/
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static inline bool hmm_range_valid(struct hmm_range *range)
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{
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return range->valid;
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}
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/*
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* hmm_device_entry_to_page() - return struct page pointed to by a device entry
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* @range: range use to decode device entry value
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* @entry: device entry value to get corresponding struct page from
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* Returns: struct page pointer if entry is a valid, NULL otherwise
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*
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* If the device entry is valid (ie valid flag set) then return the struct page
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* matching the entry value. Otherwise return NULL.
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*/
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static inline struct page *hmm_device_entry_to_page(const struct hmm_range *range,
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uint64_t entry)
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{
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if (entry == range->values[HMM_PFN_NONE])
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return NULL;
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if (entry == range->values[HMM_PFN_ERROR])
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return NULL;
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if (entry == range->values[HMM_PFN_SPECIAL])
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return NULL;
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if (!(entry & range->flags[HMM_PFN_VALID]))
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return NULL;
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return pfn_to_page(entry >> range->pfn_shift);
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}
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/*
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* hmm_device_entry_to_pfn() - return pfn value store in a device entry
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* @range: range use to decode device entry value
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* @entry: device entry to extract pfn from
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* Returns: pfn value if device entry is valid, -1UL otherwise
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*/
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static inline unsigned long
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hmm_device_entry_to_pfn(const struct hmm_range *range, uint64_t pfn)
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{
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if (pfn == range->values[HMM_PFN_NONE])
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return -1UL;
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if (pfn == range->values[HMM_PFN_ERROR])
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return -1UL;
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if (pfn == range->values[HMM_PFN_SPECIAL])
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return -1UL;
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if (!(pfn & range->flags[HMM_PFN_VALID]))
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return -1UL;
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return (pfn >> range->pfn_shift);
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}
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/*
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* hmm_device_entry_from_page() - create a valid device entry for a page
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* @range: range use to encode HMM pfn value
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* @page: page for which to create the device entry
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* Returns: valid device entry for the page
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*/
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static inline uint64_t hmm_device_entry_from_page(const struct hmm_range *range,
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struct page *page)
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{
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return (page_to_pfn(page) << range->pfn_shift) |
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range->flags[HMM_PFN_VALID];
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}
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/*
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* hmm_device_entry_from_pfn() - create a valid device entry value from pfn
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* @range: range use to encode HMM pfn value
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* @pfn: pfn value for which to create the device entry
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* Returns: valid device entry for the pfn
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*/
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static inline uint64_t hmm_device_entry_from_pfn(const struct hmm_range *range,
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unsigned long pfn)
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{
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return (pfn << range->pfn_shift) |
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range->flags[HMM_PFN_VALID];
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}
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/*
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* Old API:
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* hmm_pfn_to_page()
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* hmm_pfn_to_pfn()
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* hmm_pfn_from_page()
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* hmm_pfn_from_pfn()
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*
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* This are the OLD API please use new API, it is here to avoid cross-tree
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* merge painfullness ie we convert things to new API in stages.
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*/
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static inline struct page *hmm_pfn_to_page(const struct hmm_range *range,
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uint64_t pfn)
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{
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return hmm_device_entry_to_page(range, pfn);
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}
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static inline unsigned long hmm_pfn_to_pfn(const struct hmm_range *range,
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uint64_t pfn)
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{
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return hmm_device_entry_to_pfn(range, pfn);
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}
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static inline uint64_t hmm_pfn_from_page(const struct hmm_range *range,
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struct page *page)
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{
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return hmm_device_entry_from_page(range, page);
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}
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static inline uint64_t hmm_pfn_from_pfn(const struct hmm_range *range,
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unsigned long pfn)
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{
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return hmm_device_entry_from_pfn(range, pfn);
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}
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#if IS_ENABLED(CONFIG_HMM_MIRROR)
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/*
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* Mirroring: how to synchronize device page table with CPU page table.
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*
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* A device driver that is participating in HMM mirroring must always
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* synchronize with CPU page table updates. For this, device drivers can either
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* directly use mmu_notifier APIs or they can use the hmm_mirror API. Device
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* drivers can decide to register one mirror per device per process, or just
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* one mirror per process for a group of devices. The pattern is:
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*
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* int device_bind_address_space(..., struct mm_struct *mm, ...)
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* {
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* struct device_address_space *das;
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*
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* // Device driver specific initialization, and allocation of das
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* // which contains an hmm_mirror struct as one of its fields.
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* ...
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*
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* ret = hmm_mirror_register(&das->mirror, mm, &device_mirror_ops);
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* if (ret) {
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* // Cleanup on error
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* return ret;
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* }
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*
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* // Other device driver specific initialization
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* ...
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* }
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*
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* Once an hmm_mirror is registered for an address space, the device driver
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* will get callbacks through sync_cpu_device_pagetables() operation (see
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* hmm_mirror_ops struct).
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*
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* Device driver must not free the struct containing the hmm_mirror struct
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* before calling hmm_mirror_unregister(). The expected usage is to do that when
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* the device driver is unbinding from an address space.
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*
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*
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* void device_unbind_address_space(struct device_address_space *das)
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* {
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* // Device driver specific cleanup
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* ...
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*
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* hmm_mirror_unregister(&das->mirror);
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*
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* // Other device driver specific cleanup, and now das can be freed
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* ...
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* }
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*/
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struct hmm_mirror;
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/*
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* enum hmm_update_event - type of update
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* @HMM_UPDATE_INVALIDATE: invalidate range (no indication as to why)
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*/
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enum hmm_update_event {
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HMM_UPDATE_INVALIDATE,
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};
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/*
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* struct hmm_update - HMM update informations for callback
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*
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* @start: virtual start address of the range to update
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* @end: virtual end address of the range to update
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* @event: event triggering the update (what is happening)
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* @blockable: can the callback block/sleep ?
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*/
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struct hmm_update {
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unsigned long start;
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unsigned long end;
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enum hmm_update_event event;
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bool blockable;
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};
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/*
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* struct hmm_mirror_ops - HMM mirror device operations callback
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*
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* @update: callback to update range on a device
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*/
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struct hmm_mirror_ops {
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/* release() - release hmm_mirror
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*
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* @mirror: pointer to struct hmm_mirror
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*
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* This is called when the mm_struct is being released.
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* The callback should make sure no references to the mirror occur
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* after the callback returns.
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*/
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void (*release)(struct hmm_mirror *mirror);
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/* sync_cpu_device_pagetables() - synchronize page tables
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*
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* @mirror: pointer to struct hmm_mirror
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* @update: update informations (see struct hmm_update)
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* Returns: -EAGAIN if update.blockable false and callback need to
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* block, 0 otherwise.
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*
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* This callback ultimately originates from mmu_notifiers when the CPU
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* page table is updated. The device driver must update its page table
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* in response to this callback. The update argument tells what action
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* to perform.
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*
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* The device driver must not return from this callback until the device
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* page tables are completely updated (TLBs flushed, etc); this is a
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* synchronous call.
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*/
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int (*sync_cpu_device_pagetables)(struct hmm_mirror *mirror,
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const struct hmm_update *update);
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};
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/*
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* struct hmm_mirror - mirror struct for a device driver
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*
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* @hmm: pointer to struct hmm (which is unique per mm_struct)
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* @ops: device driver callback for HMM mirror operations
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* @list: for list of mirrors of a given mm
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*
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* Each address space (mm_struct) being mirrored by a device must register one
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* instance of an hmm_mirror struct with HMM. HMM will track the list of all
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* mirrors for each mm_struct.
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*/
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struct hmm_mirror {
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struct hmm *hmm;
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const struct hmm_mirror_ops *ops;
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struct list_head list;
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};
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int hmm_mirror_register(struct hmm_mirror *mirror, struct mm_struct *mm);
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void hmm_mirror_unregister(struct hmm_mirror *mirror);
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/*
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* hmm_mirror_mm_is_alive() - test if mm is still alive
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* @mirror: the HMM mm mirror for which we want to lock the mmap_sem
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* Returns: false if the mm is dead, true otherwise
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*
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* This is an optimization it will not accurately always return -EINVAL if the
|
|
* mm is dead ie there can be false negative (process is being kill but HMM is
|
|
* not yet inform of that). It is only intented to be use to optimize out case
|
|
* where driver is about to do something time consuming and it would be better
|
|
* to skip it if the mm is dead.
|
|
*/
|
|
static inline bool hmm_mirror_mm_is_alive(struct hmm_mirror *mirror)
|
|
{
|
|
struct mm_struct *mm;
|
|
|
|
if (!mirror || !mirror->hmm)
|
|
return false;
|
|
mm = READ_ONCE(mirror->hmm->mm);
|
|
if (mirror->hmm->dead || !mm)
|
|
return false;
|
|
|
|
return true;
|
|
}
|
|
|
|
|
|
/*
|
|
* Please see Documentation/vm/hmm.rst for how to use the range API.
|
|
*/
|
|
int hmm_range_register(struct hmm_range *range,
|
|
struct mm_struct *mm,
|
|
unsigned long start,
|
|
unsigned long end,
|
|
unsigned page_shift);
|
|
void hmm_range_unregister(struct hmm_range *range);
|
|
long hmm_range_snapshot(struct hmm_range *range);
|
|
long hmm_range_fault(struct hmm_range *range, bool block);
|
|
long hmm_range_dma_map(struct hmm_range *range,
|
|
struct device *device,
|
|
dma_addr_t *daddrs,
|
|
bool block);
|
|
long hmm_range_dma_unmap(struct hmm_range *range,
|
|
struct vm_area_struct *vma,
|
|
struct device *device,
|
|
dma_addr_t *daddrs,
|
|
bool dirty);
|
|
|
|
/*
|
|
* HMM_RANGE_DEFAULT_TIMEOUT - default timeout (ms) when waiting for a range
|
|
*
|
|
* When waiting for mmu notifiers we need some kind of time out otherwise we
|
|
* could potentialy wait for ever, 1000ms ie 1s sounds like a long time to
|
|
* wait already.
|
|
*/
|
|
#define HMM_RANGE_DEFAULT_TIMEOUT 1000
|
|
|
|
/* This is a temporary helper to avoid merge conflict between trees. */
|
|
static inline bool hmm_vma_range_done(struct hmm_range *range)
|
|
{
|
|
bool ret = hmm_range_valid(range);
|
|
|
|
hmm_range_unregister(range);
|
|
return ret;
|
|
}
|
|
|
|
/* This is a temporary helper to avoid merge conflict between trees. */
|
|
static inline int hmm_vma_fault(struct hmm_range *range, bool block)
|
|
{
|
|
long ret;
|
|
|
|
/*
|
|
* With the old API the driver must set each individual entries with
|
|
* the requested flags (valid, write, ...). So here we set the mask to
|
|
* keep intact the entries provided by the driver and zero out the
|
|
* default_flags.
|
|
*/
|
|
range->default_flags = 0;
|
|
range->pfn_flags_mask = -1UL;
|
|
|
|
ret = hmm_range_register(range, range->vma->vm_mm,
|
|
range->start, range->end,
|
|
PAGE_SHIFT);
|
|
if (ret)
|
|
return (int)ret;
|
|
|
|
if (!hmm_range_wait_until_valid(range, HMM_RANGE_DEFAULT_TIMEOUT)) {
|
|
/*
|
|
* The mmap_sem was taken by driver we release it here and
|
|
* returns -EAGAIN which correspond to mmap_sem have been
|
|
* drop in the old API.
|
|
*/
|
|
up_read(&range->vma->vm_mm->mmap_sem);
|
|
return -EAGAIN;
|
|
}
|
|
|
|
ret = hmm_range_fault(range, block);
|
|
if (ret <= 0) {
|
|
if (ret == -EBUSY || !ret) {
|
|
/* Same as above drop mmap_sem to match old API. */
|
|
up_read(&range->vma->vm_mm->mmap_sem);
|
|
ret = -EBUSY;
|
|
} else if (ret == -EAGAIN)
|
|
ret = -EBUSY;
|
|
hmm_range_unregister(range);
|
|
return ret;
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
/* Below are for HMM internal use only! Not to be used by device driver! */
|
|
void hmm_mm_destroy(struct mm_struct *mm);
|
|
|
|
static inline void hmm_mm_init(struct mm_struct *mm)
|
|
{
|
|
mm->hmm = NULL;
|
|
}
|
|
#else /* IS_ENABLED(CONFIG_HMM_MIRROR) */
|
|
static inline void hmm_mm_destroy(struct mm_struct *mm) {}
|
|
static inline void hmm_mm_init(struct mm_struct *mm) {}
|
|
#endif /* IS_ENABLED(CONFIG_HMM_MIRROR) */
|
|
|
|
#if IS_ENABLED(CONFIG_DEVICE_PRIVATE)
|
|
struct hmm_devmem;
|
|
|
|
struct page *hmm_vma_alloc_locked_page(struct vm_area_struct *vma,
|
|
unsigned long addr);
|
|
|
|
/*
|
|
* struct hmm_devmem_ops - callback for ZONE_DEVICE memory events
|
|
*
|
|
* @free: call when refcount on page reach 1 and thus is no longer use
|
|
* @fault: call when there is a page fault to unaddressable memory
|
|
*
|
|
* Both callback happens from page_free() and page_fault() callback of struct
|
|
* dev_pagemap respectively. See include/linux/memremap.h for more details on
|
|
* those.
|
|
*
|
|
* The hmm_devmem_ops callback are just here to provide a coherent and
|
|
* uniq API to device driver and device driver should not register their
|
|
* own page_free() or page_fault() but rely on the hmm_devmem_ops call-
|
|
* back.
|
|
*/
|
|
struct hmm_devmem_ops {
|
|
/*
|
|
* free() - free a device page
|
|
* @devmem: device memory structure (see struct hmm_devmem)
|
|
* @page: pointer to struct page being freed
|
|
*
|
|
* Call back occurs whenever a device page refcount reach 1 which
|
|
* means that no one is holding any reference on the page anymore
|
|
* (ZONE_DEVICE page have an elevated refcount of 1 as default so
|
|
* that they are not release to the general page allocator).
|
|
*
|
|
* Note that callback has exclusive ownership of the page (as no
|
|
* one is holding any reference).
|
|
*/
|
|
void (*free)(struct hmm_devmem *devmem, struct page *page);
|
|
/*
|
|
* fault() - CPU page fault or get user page (GUP)
|
|
* @devmem: device memory structure (see struct hmm_devmem)
|
|
* @vma: virtual memory area containing the virtual address
|
|
* @addr: virtual address that faulted or for which there is a GUP
|
|
* @page: pointer to struct page backing virtual address (unreliable)
|
|
* @flags: FAULT_FLAG_* (see include/linux/mm.h)
|
|
* @pmdp: page middle directory
|
|
* Returns: VM_FAULT_MINOR/MAJOR on success or one of VM_FAULT_ERROR
|
|
* on error
|
|
*
|
|
* The callback occurs whenever there is a CPU page fault or GUP on a
|
|
* virtual address. This means that the device driver must migrate the
|
|
* page back to regular memory (CPU accessible).
|
|
*
|
|
* The device driver is free to migrate more than one page from the
|
|
* fault() callback as an optimization. However if device decide to
|
|
* migrate more than one page it must always priotirize the faulting
|
|
* address over the others.
|
|
*
|
|
* The struct page pointer is only given as an hint to allow quick
|
|
* lookup of internal device driver data. A concurrent migration
|
|
* might have already free that page and the virtual address might
|
|
* not longer be back by it. So it should not be modified by the
|
|
* callback.
|
|
*
|
|
* Note that mmap semaphore is held in read mode at least when this
|
|
* callback occurs, hence the vma is valid upon callback entry.
|
|
*/
|
|
vm_fault_t (*fault)(struct hmm_devmem *devmem,
|
|
struct vm_area_struct *vma,
|
|
unsigned long addr,
|
|
const struct page *page,
|
|
unsigned int flags,
|
|
pmd_t *pmdp);
|
|
};
|
|
|
|
/*
|
|
* struct hmm_devmem - track device memory
|
|
*
|
|
* @completion: completion object for device memory
|
|
* @pfn_first: first pfn for this resource (set by hmm_devmem_add())
|
|
* @pfn_last: last pfn for this resource (set by hmm_devmem_add())
|
|
* @resource: IO resource reserved for this chunk of memory
|
|
* @pagemap: device page map for that chunk
|
|
* @device: device to bind resource to
|
|
* @ops: memory operations callback
|
|
* @ref: per CPU refcount
|
|
* @page_fault: callback when CPU fault on an unaddressable device page
|
|
*
|
|
* This an helper structure for device drivers that do not wish to implement
|
|
* the gory details related to hotplugging new memoy and allocating struct
|
|
* pages.
|
|
*
|
|
* Device drivers can directly use ZONE_DEVICE memory on their own if they
|
|
* wish to do so.
|
|
*
|
|
* The page_fault() callback must migrate page back, from device memory to
|
|
* system memory, so that the CPU can access it. This might fail for various
|
|
* reasons (device issues, device have been unplugged, ...). When such error
|
|
* conditions happen, the page_fault() callback must return VM_FAULT_SIGBUS and
|
|
* set the CPU page table entry to "poisoned".
|
|
*
|
|
* Note that because memory cgroup charges are transferred to the device memory,
|
|
* this should never fail due to memory restrictions. However, allocation
|
|
* of a regular system page might still fail because we are out of memory. If
|
|
* that happens, the page_fault() callback must return VM_FAULT_OOM.
|
|
*
|
|
* The page_fault() callback can also try to migrate back multiple pages in one
|
|
* chunk, as an optimization. It must, however, prioritize the faulting address
|
|
* over all the others.
|
|
*/
|
|
typedef vm_fault_t (*dev_page_fault_t)(struct vm_area_struct *vma,
|
|
unsigned long addr,
|
|
const struct page *page,
|
|
unsigned int flags,
|
|
pmd_t *pmdp);
|
|
|
|
struct hmm_devmem {
|
|
struct completion completion;
|
|
unsigned long pfn_first;
|
|
unsigned long pfn_last;
|
|
struct resource *resource;
|
|
struct device *device;
|
|
struct dev_pagemap pagemap;
|
|
const struct hmm_devmem_ops *ops;
|
|
struct percpu_ref ref;
|
|
dev_page_fault_t page_fault;
|
|
};
|
|
|
|
/*
|
|
* To add (hotplug) device memory, HMM assumes that there is no real resource
|
|
* that reserves a range in the physical address space (this is intended to be
|
|
* use by unaddressable device memory). It will reserve a physical range big
|
|
* enough and allocate struct page for it.
|
|
*
|
|
* The device driver can wrap the hmm_devmem struct inside a private device
|
|
* driver struct.
|
|
*/
|
|
struct hmm_devmem *hmm_devmem_add(const struct hmm_devmem_ops *ops,
|
|
struct device *device,
|
|
unsigned long size);
|
|
|
|
/*
|
|
* hmm_devmem_page_set_drvdata - set per-page driver data field
|
|
*
|
|
* @page: pointer to struct page
|
|
* @data: driver data value to set
|
|
*
|
|
* Because page can not be on lru we have an unsigned long that driver can use
|
|
* to store a per page field. This just a simple helper to do that.
|
|
*/
|
|
static inline void hmm_devmem_page_set_drvdata(struct page *page,
|
|
unsigned long data)
|
|
{
|
|
page->hmm_data = data;
|
|
}
|
|
|
|
/*
|
|
* hmm_devmem_page_get_drvdata - get per page driver data field
|
|
*
|
|
* @page: pointer to struct page
|
|
* Return: driver data value
|
|
*/
|
|
static inline unsigned long hmm_devmem_page_get_drvdata(const struct page *page)
|
|
{
|
|
return page->hmm_data;
|
|
}
|
|
#endif /* CONFIG_DEVICE_PRIVATE */
|
|
#else /* IS_ENABLED(CONFIG_HMM) */
|
|
static inline void hmm_mm_destroy(struct mm_struct *mm) {}
|
|
static inline void hmm_mm_init(struct mm_struct *mm) {}
|
|
#endif /* IS_ENABLED(CONFIG_HMM) */
|
|
|
|
#endif /* LINUX_HMM_H */
|