linux_dsm_epyc7002/include/linux/hmm.h
Jérôme Glisse 63d5066f6e mm/hmm: mirror hugetlbfs (snapshoting, faulting and DMA mapping)
HMM mirror is a device driver helpers to mirror range of virtual address.
It means that the process jobs running on the device can access the same
virtual address as the CPU threads of that process.  This patch adds
support for hugetlbfs mapping (ie range of virtual address that are mmap
of a hugetlbfs).

[rcampbell@nvidia.com: fix initial PFN for hugetlbfs pages]
  Link: http://lkml.kernel.org/r/20190419233536.8080-1-rcampbell@nvidia.com
Link: http://lkml.kernel.org/r/20190403193318.16478-9-jglisse@redhat.com
Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
Signed-off-by: Ralph Campbell <rcampbell@nvidia.com>
Reviewed-by: Ralph Campbell <rcampbell@nvidia.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Souptick Joarder <jrdr.linux@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-05-14 09:47:48 -07:00

722 lines
24 KiB
C

/*
* Copyright 2013 Red Hat Inc.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* Authors: Jérôme Glisse <jglisse@redhat.com>
*/
/*
* Heterogeneous Memory Management (HMM)
*
* See Documentation/vm/hmm.rst for reasons and overview of what HMM is and it
* is for. Here we focus on the HMM API description, with some explanation of
* the underlying implementation.
*
* Short description: HMM provides a set of helpers to share a virtual address
* space between CPU and a device, so that the device can access any valid
* address of the process (while still obeying memory protection). HMM also
* provides helpers to migrate process memory to device memory, and back. Each
* set of functionality (address space mirroring, and migration to and from
* device memory) can be used independently of the other.
*
*
* HMM address space mirroring API:
*
* Use HMM address space mirroring if you want to mirror range of the CPU page
* table of a process into a device page table. Here, "mirror" means "keep
* synchronized". Prerequisites: the device must provide the ability to write-
* protect its page tables (at PAGE_SIZE granularity), and must be able to
* recover from the resulting potential page faults.
*
* HMM guarantees that at any point in time, a given virtual address points to
* either the same memory in both CPU and device page tables (that is: CPU and
* device page tables each point to the same pages), or that one page table (CPU
* or device) points to no entry, while the other still points to the old page
* for the address. The latter case happens when the CPU page table update
* happens first, and then the update is mirrored over to the device page table.
* This does not cause any issue, because the CPU page table cannot start
* pointing to a new page until the device page table is invalidated.
*
* HMM uses mmu_notifiers to monitor the CPU page tables, and forwards any
* updates to each device driver that has registered a mirror. It also provides
* some API calls to help with taking a snapshot of the CPU page table, and to
* synchronize with any updates that might happen concurrently.
*
*
* HMM migration to and from device memory:
*
* HMM provides a set of helpers to hotplug device memory as ZONE_DEVICE, with
* a new MEMORY_DEVICE_PRIVATE type. This provides a struct page for each page
* of the device memory, and allows the device driver to manage its memory
* using those struct pages. Having struct pages for device memory makes
* migration easier. Because that memory is not addressable by the CPU it must
* never be pinned to the device; in other words, any CPU page fault can always
* cause the device memory to be migrated (copied/moved) back to regular memory.
*
* A new migrate helper (migrate_vma()) has been added (see mm/migrate.c) that
* allows use of a device DMA engine to perform the copy operation between
* regular system memory and device memory.
*/
#ifndef LINUX_HMM_H
#define LINUX_HMM_H
#include <linux/kconfig.h>
#include <asm/pgtable.h>
#if IS_ENABLED(CONFIG_HMM)
#include <linux/device.h>
#include <linux/migrate.h>
#include <linux/memremap.h>
#include <linux/completion.h>
#include <linux/mmu_notifier.h>
/*
* struct hmm - HMM per mm struct
*
* @mm: mm struct this HMM struct is bound to
* @lock: lock protecting ranges list
* @ranges: list of range being snapshotted
* @mirrors: list of mirrors for this mm
* @mmu_notifier: mmu notifier to track updates to CPU page table
* @mirrors_sem: read/write semaphore protecting the mirrors list
* @wq: wait queue for user waiting on a range invalidation
* @notifiers: count of active mmu notifiers
* @dead: is the mm dead ?
*/
struct hmm {
struct mm_struct *mm;
struct kref kref;
struct mutex lock;
struct list_head ranges;
struct list_head mirrors;
struct mmu_notifier mmu_notifier;
struct rw_semaphore mirrors_sem;
wait_queue_head_t wq;
long notifiers;
bool dead;
};
/*
* hmm_pfn_flag_e - HMM flag enums
*
* Flags:
* HMM_PFN_VALID: pfn is valid. It has, at least, read permission.
* HMM_PFN_WRITE: CPU page table has write permission set
* HMM_PFN_DEVICE_PRIVATE: private device memory (ZONE_DEVICE)
*
* The driver provide a flags array, if driver valid bit for an entry is bit
* 3 ie (entry & (1 << 3)) is true if entry is valid then driver must provide
* an array in hmm_range.flags with hmm_range.flags[HMM_PFN_VALID] == 1 << 3.
* Same logic apply to all flags. This is same idea as vm_page_prot in vma
* except that this is per device driver rather than per architecture.
*/
enum hmm_pfn_flag_e {
HMM_PFN_VALID = 0,
HMM_PFN_WRITE,
HMM_PFN_DEVICE_PRIVATE,
HMM_PFN_FLAG_MAX
};
/*
* hmm_pfn_value_e - HMM pfn special value
*
* Flags:
* HMM_PFN_ERROR: corresponding CPU page table entry points to poisoned memory
* HMM_PFN_NONE: corresponding CPU page table entry is pte_none()
* HMM_PFN_SPECIAL: corresponding CPU page table entry is special; i.e., the
* result of vmf_insert_pfn() or vm_insert_page(). Therefore, it should not
* be mirrored by a device, because the entry will never have HMM_PFN_VALID
* set and the pfn value is undefined.
*
* Driver provide entry value for none entry, error entry and special entry,
* driver can alias (ie use same value for error and special for instance). It
* should not alias none and error or special.
*
* HMM pfn value returned by hmm_vma_get_pfns() or hmm_vma_fault() will be:
* hmm_range.values[HMM_PFN_ERROR] if CPU page table entry is poisonous,
* hmm_range.values[HMM_PFN_NONE] if there is no CPU page table
* hmm_range.values[HMM_PFN_SPECIAL] if CPU page table entry is a special one
*/
enum hmm_pfn_value_e {
HMM_PFN_ERROR,
HMM_PFN_NONE,
HMM_PFN_SPECIAL,
HMM_PFN_VALUE_MAX
};
/*
* struct hmm_range - track invalidation lock on virtual address range
*
* @hmm: the core HMM structure this range is active against
* @vma: the vm area struct for the range
* @list: all range lock are on a list
* @start: range virtual start address (inclusive)
* @end: range virtual end address (exclusive)
* @pfns: array of pfns (big enough for the range)
* @flags: pfn flags to match device driver page table
* @values: pfn value for some special case (none, special, error, ...)
* @default_flags: default flags for the range (write, read, ... see hmm doc)
* @pfn_flags_mask: allows to mask pfn flags so that only default_flags matter
* @pfn_shifts: pfn shift value (should be <= PAGE_SHIFT)
* @valid: pfns array did not change since it has been fill by an HMM function
*/
struct hmm_range {
struct hmm *hmm;
struct vm_area_struct *vma;
struct list_head list;
unsigned long start;
unsigned long end;
uint64_t *pfns;
const uint64_t *flags;
const uint64_t *values;
uint64_t default_flags;
uint64_t pfn_flags_mask;
uint8_t page_shift;
uint8_t pfn_shift;
bool valid;
};
/*
* hmm_range_page_shift() - return the page shift for the range
* @range: range being queried
* Returns: page shift (page size = 1 << page shift) for the range
*/
static inline unsigned hmm_range_page_shift(const struct hmm_range *range)
{
return range->page_shift;
}
/*
* hmm_range_page_size() - return the page size for the range
* @range: range being queried
* Returns: page size for the range in bytes
*/
static inline unsigned long hmm_range_page_size(const struct hmm_range *range)
{
return 1UL << hmm_range_page_shift(range);
}
/*
* hmm_range_wait_until_valid() - wait for range to be valid
* @range: range affected by invalidation to wait on
* @timeout: time out for wait in ms (ie abort wait after that period of time)
* Returns: true if the range is valid, false otherwise.
*/
static inline bool hmm_range_wait_until_valid(struct hmm_range *range,
unsigned long timeout)
{
/* Check if mm is dead ? */
if (range->hmm == NULL || range->hmm->dead || range->hmm->mm == NULL) {
range->valid = false;
return false;
}
if (range->valid)
return true;
wait_event_timeout(range->hmm->wq, range->valid || range->hmm->dead,
msecs_to_jiffies(timeout));
/* Return current valid status just in case we get lucky */
return range->valid;
}
/*
* hmm_range_valid() - test if a range is valid or not
* @range: range
* Returns: true if the range is valid, false otherwise.
*/
static inline bool hmm_range_valid(struct hmm_range *range)
{
return range->valid;
}
/*
* hmm_pfn_to_page() - return struct page pointed to by a valid HMM pfn
* @range: range use to decode HMM pfn value
* @pfn: HMM pfn value to get corresponding struct page from
* Returns: struct page pointer if pfn is a valid HMM pfn, NULL otherwise
*
* If the HMM pfn is valid (ie valid flag set) then return the struct page
* matching the pfn value stored in the HMM pfn. Otherwise return NULL.
*/
static inline struct page *hmm_pfn_to_page(const struct hmm_range *range,
uint64_t pfn)
{
if (pfn == range->values[HMM_PFN_NONE])
return NULL;
if (pfn == range->values[HMM_PFN_ERROR])
return NULL;
if (pfn == range->values[HMM_PFN_SPECIAL])
return NULL;
if (!(pfn & range->flags[HMM_PFN_VALID]))
return NULL;
return pfn_to_page(pfn >> range->pfn_shift);
}
/*
* hmm_pfn_to_pfn() - return pfn value store in a HMM pfn
* @range: range use to decode HMM pfn value
* @pfn: HMM pfn value to extract pfn from
* Returns: pfn value if HMM pfn is valid, -1UL otherwise
*/
static inline unsigned long hmm_pfn_to_pfn(const struct hmm_range *range,
uint64_t pfn)
{
if (pfn == range->values[HMM_PFN_NONE])
return -1UL;
if (pfn == range->values[HMM_PFN_ERROR])
return -1UL;
if (pfn == range->values[HMM_PFN_SPECIAL])
return -1UL;
if (!(pfn & range->flags[HMM_PFN_VALID]))
return -1UL;
return (pfn >> range->pfn_shift);
}
/*
* hmm_pfn_from_page() - create a valid HMM pfn value from struct page
* @range: range use to encode HMM pfn value
* @page: struct page pointer for which to create the HMM pfn
* Returns: valid HMM pfn for the page
*/
static inline uint64_t hmm_pfn_from_page(const struct hmm_range *range,
struct page *page)
{
return (page_to_pfn(page) << range->pfn_shift) |
range->flags[HMM_PFN_VALID];
}
/*
* hmm_pfn_from_pfn() - create a valid HMM pfn value from pfn
* @range: range use to encode HMM pfn value
* @pfn: pfn value for which to create the HMM pfn
* Returns: valid HMM pfn for the pfn
*/
static inline uint64_t hmm_pfn_from_pfn(const struct hmm_range *range,
unsigned long pfn)
{
return (pfn << range->pfn_shift) |
range->flags[HMM_PFN_VALID];
}
#if IS_ENABLED(CONFIG_HMM_MIRROR)
/*
* Mirroring: how to synchronize device page table with CPU page table.
*
* A device driver that is participating in HMM mirroring must always
* synchronize with CPU page table updates. For this, device drivers can either
* directly use mmu_notifier APIs or they can use the hmm_mirror API. Device
* drivers can decide to register one mirror per device per process, or just
* one mirror per process for a group of devices. The pattern is:
*
* int device_bind_address_space(..., struct mm_struct *mm, ...)
* {
* struct device_address_space *das;
*
* // Device driver specific initialization, and allocation of das
* // which contains an hmm_mirror struct as one of its fields.
* ...
*
* ret = hmm_mirror_register(&das->mirror, mm, &device_mirror_ops);
* if (ret) {
* // Cleanup on error
* return ret;
* }
*
* // Other device driver specific initialization
* ...
* }
*
* Once an hmm_mirror is registered for an address space, the device driver
* will get callbacks through sync_cpu_device_pagetables() operation (see
* hmm_mirror_ops struct).
*
* Device driver must not free the struct containing the hmm_mirror struct
* before calling hmm_mirror_unregister(). The expected usage is to do that when
* the device driver is unbinding from an address space.
*
*
* void device_unbind_address_space(struct device_address_space *das)
* {
* // Device driver specific cleanup
* ...
*
* hmm_mirror_unregister(&das->mirror);
*
* // Other device driver specific cleanup, and now das can be freed
* ...
* }
*/
struct hmm_mirror;
/*
* enum hmm_update_event - type of update
* @HMM_UPDATE_INVALIDATE: invalidate range (no indication as to why)
*/
enum hmm_update_event {
HMM_UPDATE_INVALIDATE,
};
/*
* struct hmm_update - HMM update informations for callback
*
* @start: virtual start address of the range to update
* @end: virtual end address of the range to update
* @event: event triggering the update (what is happening)
* @blockable: can the callback block/sleep ?
*/
struct hmm_update {
unsigned long start;
unsigned long end;
enum hmm_update_event event;
bool blockable;
};
/*
* struct hmm_mirror_ops - HMM mirror device operations callback
*
* @update: callback to update range on a device
*/
struct hmm_mirror_ops {
/* release() - release hmm_mirror
*
* @mirror: pointer to struct hmm_mirror
*
* This is called when the mm_struct is being released.
* The callback should make sure no references to the mirror occur
* after the callback returns.
*/
void (*release)(struct hmm_mirror *mirror);
/* sync_cpu_device_pagetables() - synchronize page tables
*
* @mirror: pointer to struct hmm_mirror
* @update: update informations (see struct hmm_update)
* Returns: -EAGAIN if update.blockable false and callback need to
* block, 0 otherwise.
*
* This callback ultimately originates from mmu_notifiers when the CPU
* page table is updated. The device driver must update its page table
* in response to this callback. The update argument tells what action
* to perform.
*
* The device driver must not return from this callback until the device
* page tables are completely updated (TLBs flushed, etc); this is a
* synchronous call.
*/
int (*sync_cpu_device_pagetables)(struct hmm_mirror *mirror,
const struct hmm_update *update);
};
/*
* struct hmm_mirror - mirror struct for a device driver
*
* @hmm: pointer to struct hmm (which is unique per mm_struct)
* @ops: device driver callback for HMM mirror operations
* @list: for list of mirrors of a given mm
*
* Each address space (mm_struct) being mirrored by a device must register one
* instance of an hmm_mirror struct with HMM. HMM will track the list of all
* mirrors for each mm_struct.
*/
struct hmm_mirror {
struct hmm *hmm;
const struct hmm_mirror_ops *ops;
struct list_head list;
};
int hmm_mirror_register(struct hmm_mirror *mirror, struct mm_struct *mm);
void hmm_mirror_unregister(struct hmm_mirror *mirror);
/*
* 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);
/*
* 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) || IS_ENABLED(CONFIG_DEVICE_PUBLIC)
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);
struct hmm_devmem *hmm_devmem_add_resource(const struct hmm_devmem_ops *ops,
struct device *device,
struct resource *res);
/*
* 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;
}
/*
* struct hmm_device - fake device to hang device memory onto
*
* @device: device struct
* @minor: device minor number
*/
struct hmm_device {
struct device device;
unsigned int minor;
};
/*
* A device driver that wants to handle multiple devices memory through a
* single fake device can use hmm_device to do so. This is purely a helper and
* it is not strictly needed, in order to make use of any HMM functionality.
*/
struct hmm_device *hmm_device_new(void *drvdata);
void hmm_device_put(struct hmm_device *hmm_device);
#endif /* CONFIG_DEVICE_PRIVATE || CONFIG_DEVICE_PUBLIC */
#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 */