From 2076e5c0451ca943ff8ecc6def7239c84c77e070 Mon Sep 17 00:00:00 2001 From: Ralph Campbell Date: Mon, 6 May 2019 16:29:38 -0700 Subject: mm/hmm: update HMM documentation MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Update the HMM documentation to reflect the latest API and make a few minor wording changes. Cc: John Hubbard Cc: Ira Weiny Cc: Dan Williams Cc: Arnd Bergmann Cc: Balbir Singh Cc: Dan Carpenter Cc: Matthew Wilcox Cc: Souptick Joarder Cc: Andrew Morton Signed-off-by: Ralph Campbell Reviewed-by: Jérôme Glisse Signed-off-by: Jason Gunthorpe --- Documentation/vm/hmm.rst | 141 +++++++++++++++++++++++++---------------------- 1 file changed, 74 insertions(+), 67 deletions(-) (limited to 'Documentation/vm') diff --git a/Documentation/vm/hmm.rst b/Documentation/vm/hmm.rst index 7cdf7282e022..7b6eeda5a7c0 100644 --- a/Documentation/vm/hmm.rst +++ b/Documentation/vm/hmm.rst @@ -10,7 +10,7 @@ of this being specialized struct page for such memory (see sections 5 to 7 of this document). HMM also provides optional helpers for SVM (Share Virtual Memory), i.e., -allowing a device to transparently access program address coherently with +allowing a device to transparently access program addresses coherently with the CPU meaning that any valid pointer on the CPU is also a valid pointer for the device. This is becoming mandatory to simplify the use of advanced heterogeneous computing where GPU, DSP, or FPGA are used to perform various @@ -22,8 +22,8 @@ expose the hardware limitations that are inherent to many platforms. The third section gives an overview of the HMM design. The fourth section explains how CPU page-table mirroring works and the purpose of HMM in this context. The fifth section deals with how device memory is represented inside the kernel. -Finally, the last section presents a new migration helper that allows lever- -aging the device DMA engine. +Finally, the last section presents a new migration helper that allows +leveraging the device DMA engine. .. contents:: :local: @@ -39,20 +39,20 @@ address space. I use shared address space to refer to the opposite situation: i.e., one in which any application memory region can be used by a device transparently. -Split address space happens because device can only access memory allocated -through device specific API. This implies that all memory objects in a program +Split address space happens because devices can only access memory allocated +through a device specific API. This implies that all memory objects in a program are not equal from the device point of view which complicates large programs that rely on a wide set of libraries. -Concretely this means that code that wants to leverage devices like GPUs needs -to copy object between generically allocated memory (malloc, mmap private, mmap +Concretely, this means that code that wants to leverage devices like GPUs needs +to copy objects between generically allocated memory (malloc, mmap private, mmap share) and memory allocated through the device driver API (this still ends up with an mmap but of the device file). For flat data sets (array, grid, image, ...) this isn't too hard to achieve but -complex data sets (list, tree, ...) are hard to get right. Duplicating a +for complex data sets (list, tree, ...) it's hard to get right. Duplicating a complex data set needs to re-map all the pointer relations between each of its -elements. This is error prone and program gets harder to debug because of the +elements. This is error prone and programs get harder to debug because of the duplicate data set and addresses. Split address space also means that libraries cannot transparently use data @@ -77,12 +77,12 @@ I/O bus, device memory characteristics I/O buses cripple shared address spaces due to a few limitations. Most I/O buses only allow basic memory access from device to main memory; even cache -coherency is often optional. Access to device memory from CPU is even more +coherency is often optional. Access to device memory from a CPU is even more limited. More often than not, it is not cache coherent. If we only consider the PCIE bus, then a device can access main memory (often through an IOMMU) and be cache coherent with the CPUs. However, it only allows -a limited set of atomic operations from device on main memory. This is worse +a limited set of atomic operations from the device on main memory. This is worse in the other direction: the CPU can only access a limited range of the device memory and cannot perform atomic operations on it. Thus device memory cannot be considered the same as regular memory from the kernel point of view. @@ -93,20 +93,20 @@ The final limitation is latency. Access to main memory from the device has an order of magnitude higher latency than when the device accesses its own memory. Some platforms are developing new I/O buses or additions/modifications to PCIE -to address some of these limitations (OpenCAPI, CCIX). They mainly allow two- -way cache coherency between CPU and device and allow all atomic operations the +to address some of these limitations (OpenCAPI, CCIX). They mainly allow +two-way cache coherency between CPU and device and allow all atomic operations the architecture supports. Sadly, not all platforms are following this trend and some major architectures are left without hardware solutions to these problems. So for shared address space to make sense, not only must we allow devices to access any memory but we must also permit any memory to be migrated to device -memory while device is using it (blocking CPU access while it happens). +memory while the device is using it (blocking CPU access while it happens). Shared address space and migration ================================== -HMM intends to provide two main features. First one is to share the address +HMM intends to provide two main features. The first one is to share the address space by duplicating the CPU page table in the device page table so the same address points to the same physical memory for any valid main memory address in the process address space. @@ -121,14 +121,14 @@ why HMM provides helpers to factor out everything that can be while leaving the hardware specific details to the device driver. The second mechanism HMM provides is a new kind of ZONE_DEVICE memory that -allows allocating a struct page for each page of the device memory. Those pages +allows allocating a struct page for each page of device memory. Those pages are special because the CPU cannot map them. However, they allow migrating main memory to device memory using existing migration mechanisms and everything -looks like a page is swapped out to disk from the CPU point of view. Using a -struct page gives the easiest and cleanest integration with existing mm mech- -anisms. Here again, HMM only provides helpers, first to hotplug new ZONE_DEVICE +looks like a page that is swapped out to disk from the CPU point of view. Using a +struct page gives the easiest and cleanest integration with existing mm +mechanisms. Here again, HMM only provides helpers, first to hotplug new ZONE_DEVICE memory for the device memory and second to perform migration. Policy decisions -of what and when to migrate things is left to the device driver. +of what and when to migrate is left to the device driver. Note that any CPU access to a device page triggers a page fault and a migration back to main memory. For example, when a page backing a given CPU address A is @@ -136,8 +136,8 @@ migrated from a main memory page to a device page, then any CPU access to address A triggers a page fault and initiates a migration back to main memory. With these two features, HMM not only allows a device to mirror process address -space and keeping both CPU and device page table synchronized, but also lever- -ages device memory by migrating the part of the data set that is actively being +space and keeps both CPU and device page tables synchronized, but also +leverages device memory by migrating the part of the data set that is actively being used by the device. @@ -151,21 +151,28 @@ registration of an hmm_mirror struct:: int hmm_mirror_register(struct hmm_mirror *mirror, struct mm_struct *mm); - int hmm_mirror_register_locked(struct hmm_mirror *mirror, - struct mm_struct *mm); - -The locked variant is to be used when the driver is already holding mmap_sem -of the mm in write mode. The mirror struct has a set of callbacks that are used +The mirror struct has a set of callbacks that are used to propagate CPU page tables:: 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 + * must ensure that all access to any pages obtained from this mirror + * is halted before the callback returns. All future access should + * fault. + */ + void (*release)(struct hmm_mirror *mirror); + /* sync_cpu_device_pagetables() - synchronize page tables * * @mirror: pointer to struct hmm_mirror - * @update_type: type of update that occurred to the CPU page table - * @start: virtual start address of the range to update - * @end: virtual end address of the range to update + * @update: update information (see struct mmu_notifier_range) + * Return: -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 @@ -176,14 +183,12 @@ to propagate CPU page tables:: * page tables are completely updated (TLBs flushed, etc); this is a * synchronous call. */ - void (*update)(struct hmm_mirror *mirror, - enum hmm_update action, - unsigned long start, - unsigned long end); + int (*sync_cpu_device_pagetables)(struct hmm_mirror *mirror, + const struct hmm_update *update); }; The device driver must perform the update action to the range (mark range -read only, or fully unmap, ...). The device must be done with the update before +read only, or fully unmap, etc.). The device must complete the update before the driver callback returns. When the device driver wants to populate a range of virtual addresses, it can @@ -194,17 +199,18 @@ use either:: The first one (hmm_range_snapshot()) will only fetch present CPU page table entries and will not trigger a page fault on missing or non-present entries. -The second one does trigger a page fault on missing or read-only entry if the -write parameter is true. Page faults use the generic mm page fault code path -just like a CPU page fault. +The second one does trigger a page fault on missing or read-only entries if +write access is requested (see below). Page faults use the generic mm page +fault code path just like a CPU page fault. Both functions copy CPU page table entries into their pfns array argument. Each entry in that array corresponds to an address in the virtual range. HMM provides a set of flags to help the driver identify special CPU page table entries. -Locking with the update() callback is the most important aspect the driver must -respect in order to keep things properly synchronized. The usage pattern is:: +Locking within the sync_cpu_device_pagetables() callback is the most important +aspect the driver must respect in order to keep things properly synchronized. +The usage pattern is:: int driver_populate_range(...) { @@ -239,11 +245,11 @@ respect in order to keep things properly synchronized. The usage pattern is:: hmm_range_wait_until_valid(&range, TIMEOUT_IN_MSEC); goto again; } - hmm_mirror_unregister(&range); + hmm_range_unregister(&range); return ret; } take_lock(driver->update); - if (!range.valid) { + if (!hmm_range_valid(&range)) { release_lock(driver->update); up_read(&mm->mmap_sem); goto again; @@ -251,15 +257,15 @@ respect in order to keep things properly synchronized. The usage pattern is:: // Use pfns array content to update device page table - hmm_mirror_unregister(&range); + hmm_range_unregister(&range); release_lock(driver->update); up_read(&mm->mmap_sem); return 0; } The driver->update lock is the same lock that the driver takes inside its -update() callback. That lock must be held before checking the range.valid -field to avoid any race with a concurrent CPU page table update. +sync_cpu_device_pagetables() callback. That lock must be held before calling +hmm_range_valid() to avoid any race with a concurrent CPU page table update. HMM implements all this on top of the mmu_notifier API because we wanted a simpler API and also to be able to perform optimizations latter on like doing @@ -279,46 +285,47 @@ concurrently). Leverage default_flags and pfn_flags_mask ========================================= -The hmm_range struct has 2 fields default_flags and pfn_flags_mask that allows -to set fault or snapshot policy for a whole range instead of having to set them -for each entries in the range. +The hmm_range struct has 2 fields, default_flags and pfn_flags_mask, that specify +fault or snapshot policy for the whole range instead of having to set them +for each entry in the pfns array. + +For instance, if the device flags for range.flags are:: -For instance if the device flags for device entries are: - VALID (1 << 63) - WRITE (1 << 62) + range.flags[HMM_PFN_VALID] = (1 << 63); + range.flags[HMM_PFN_WRITE] = (1 << 62); -Now let say that device driver wants to fault with at least read a range then -it does set:: +and the device driver wants pages for a range with at least read permission, +it sets:: range->default_flags = (1 << 63); range->pfn_flags_mask = 0; -and calls hmm_range_fault() as described above. This will fill fault all page +and calls hmm_range_fault() as described above. This will fill fault all pages in the range with at least read permission. -Now let say driver wants to do the same except for one page in the range for -which its want to have write. Now driver set:: +Now let's say the driver wants to do the same except for one page in the range for +which it wants to have write permission. Now driver set:: range->default_flags = (1 << 63); range->pfn_flags_mask = (1 << 62); range->pfns[index_of_write] = (1 << 62); -With this HMM will fault in all page with at least read (ie valid) and for the +With this, HMM will fault in all pages with at least read (i.e., valid) and for the address == range->start + (index_of_write << PAGE_SHIFT) it will fault with -write permission ie if the CPU pte does not have write permission set then HMM +write permission i.e., if the CPU pte does not have write permission set then HMM will call handle_mm_fault(). -Note that HMM will populate the pfns array with write permission for any entry -that have write permission within the CPU pte no matter what are the values set +Note that HMM will populate the pfns array with write permission for any page +that is mapped with CPU write permission no matter what values are set in default_flags or pfn_flags_mask. Represent and manage device memory from core kernel point of view ================================================================= -Several different designs were tried to support device memory. First one used -a device specific data structure to keep information about migrated memory and -HMM hooked itself in various places of mm code to handle any access to +Several different designs were tried to support device memory. The first one +used a device specific data structure to keep information about migrated memory +and HMM hooked itself in various places of mm code to handle any access to addresses that were backed by device memory. It turns out that this ended up replicating most of the fields of struct page and also needed many kernel code paths to be updated to understand this new kind of memory. @@ -341,7 +348,7 @@ The hmm_devmem_ops is where most of the important things are:: struct hmm_devmem_ops { void (*free)(struct hmm_devmem *devmem, struct page *page); - int (*fault)(struct hmm_devmem *devmem, + vm_fault_t (*fault)(struct hmm_devmem *devmem, struct vm_area_struct *vma, unsigned long addr, struct page *page, @@ -417,9 +424,9 @@ willing to pay to keep all the code simpler. Memory cgroup (memcg) and rss accounting ======================================== -For now device memory is accounted as any regular page in rss counters (either +For now, device memory is accounted as any regular page in rss counters (either anonymous if device page is used for anonymous, file if device page is used for -file backed page or shmem if device page is used for shared memory). This is a +file backed page, or shmem if device page is used for shared memory). This is a deliberate choice to keep existing applications, that might start using device memory without knowing about it, running unimpacted. @@ -439,6 +446,6 @@ get more experience in how device memory is used and its impact on memory resource control. -Note that device memory can never be pinned by device driver nor through GUP +Note that device memory can never be pinned by a device driver nor through GUP and thus such memory is always free upon process exit. Or when last reference is dropped in case of shared memory or file backed memory. -- cgit v1.2.3 From eee3ae41b153e55e25d6cf7bd5b5098ba0afe705 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Wed, 26 Jun 2019 14:27:20 +0200 Subject: mm: remove hmm_devmem_add There isn't really much value add in the hmm_devmem_add wrapper and more, as using devm_memremap_pages directly now is just as simple. Signed-off-by: Christoph Hellwig Reviewed-by: Jason Gunthorpe Reviewed-by: Dan Williams Signed-off-by: Jason Gunthorpe --- Documentation/vm/hmm.rst | 26 ---------- include/linux/hmm.h | 129 ----------------------------------------------- mm/hmm.c | 110 ---------------------------------------- 3 files changed, 265 deletions(-) (limited to 'Documentation/vm') diff --git a/Documentation/vm/hmm.rst b/Documentation/vm/hmm.rst index 7cdf7282e022..50e1380950a9 100644 --- a/Documentation/vm/hmm.rst +++ b/Documentation/vm/hmm.rst @@ -329,32 +329,6 @@ directly using struct page for device memory which left most kernel code paths unaware of the difference. We only need to make sure that no one ever tries to map those pages from the CPU side. -HMM provides a set of helpers to register and hotplug device memory as a new -region needing a struct page. This is offered through a very simple API:: - - struct hmm_devmem *hmm_devmem_add(const struct hmm_devmem_ops *ops, - struct device *device, - unsigned long size); - void hmm_devmem_remove(struct hmm_devmem *devmem); - -The hmm_devmem_ops is where most of the important things are:: - - struct hmm_devmem_ops { - void (*free)(struct hmm_devmem *devmem, struct page *page); - int (*fault)(struct hmm_devmem *devmem, - struct vm_area_struct *vma, - unsigned long addr, - struct page *page, - unsigned flags, - pmd_t *pmdp); - }; - -The first callback (free()) happens when the last reference on a device page is -dropped. This means the device page is now free and no longer used by anyone. -The second callback happens whenever the CPU tries to access a device page -which it cannot do. This second callback must trigger a migration back to -system memory. - Migration to and from device memory =================================== diff --git a/include/linux/hmm.h b/include/linux/hmm.h index 1d55b7ea2da6..86aa4ec3404c 100644 --- a/include/linux/hmm.h +++ b/include/linux/hmm.h @@ -585,135 +585,6 @@ 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 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. - */ - -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; -}; - -/* - * 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 * diff --git a/mm/hmm.c b/mm/hmm.c index fdbd48771292..90ca0cdab9db 100644 --- a/mm/hmm.c +++ b/mm/hmm.c @@ -1327,113 +1327,3 @@ long hmm_range_dma_unmap(struct hmm_range *range, } EXPORT_SYMBOL(hmm_range_dma_unmap); #endif /* IS_ENABLED(CONFIG_HMM_MIRROR) */ - - -#if IS_ENABLED(CONFIG_DEVICE_PRIVATE) -static void hmm_devmem_ref_release(struct percpu_ref *ref) -{ - struct hmm_devmem *devmem; - - devmem = container_of(ref, struct hmm_devmem, ref); - complete(&devmem->completion); -} - -static void hmm_devmem_ref_exit(struct dev_pagemap *pgmap) -{ - struct hmm_devmem *devmem; - - devmem = container_of(pgmap, struct hmm_devmem, pagemap); - wait_for_completion(&devmem->completion); - percpu_ref_exit(pgmap->ref); -} - -static void hmm_devmem_ref_kill(struct dev_pagemap *pgmap) -{ - percpu_ref_kill(pgmap->ref); -} - -static vm_fault_t hmm_devmem_migrate_to_ram(struct vm_fault *vmf) -{ - struct hmm_devmem *devmem = - container_of(vmf->page->pgmap, struct hmm_devmem, pagemap); - - return devmem->ops->fault(devmem, vmf->vma, vmf->address, vmf->page, - vmf->flags, vmf->pmd); -} - -static void hmm_devmem_free(struct page *page) -{ - struct hmm_devmem *devmem = - container_of(page->pgmap, struct hmm_devmem, pagemap); - - devmem->ops->free(devmem, page); -} - -static const struct dev_pagemap_ops hmm_pagemap_ops = { - .page_free = hmm_devmem_free, - .kill = hmm_devmem_ref_kill, - .cleanup = hmm_devmem_ref_exit, - .migrate_to_ram = hmm_devmem_migrate_to_ram, -}; - -/* - * hmm_devmem_add() - hotplug ZONE_DEVICE memory for device memory - * - * @ops: memory event device driver callback (see struct hmm_devmem_ops) - * @device: device struct to bind the resource too - * @size: size in bytes of the device memory to add - * Returns: pointer to new hmm_devmem struct ERR_PTR otherwise - * - * This function first finds an empty range of physical address big enough to - * contain the new resource, and then hotplugs it as ZONE_DEVICE memory, which - * in turn allocates struct pages. It does not do anything beyond that; all - * events affecting the memory will go through the various callbacks provided - * by hmm_devmem_ops struct. - * - * Device driver should call this function during device initialization and - * is then responsible of memory management. HMM only provides helpers. - */ -struct hmm_devmem *hmm_devmem_add(const struct hmm_devmem_ops *ops, - struct device *device, - unsigned long size) -{ - struct hmm_devmem *devmem; - void *result; - int ret; - - devmem = devm_kzalloc(device, sizeof(*devmem), GFP_KERNEL); - if (!devmem) - return ERR_PTR(-ENOMEM); - - init_completion(&devmem->completion); - devmem->pfn_first = -1UL; - devmem->pfn_last = -1UL; - devmem->resource = NULL; - devmem->device = device; - devmem->ops = ops; - - ret = percpu_ref_init(&devmem->ref, &hmm_devmem_ref_release, - 0, GFP_KERNEL); - if (ret) - return ERR_PTR(ret); - - devmem->resource = devm_request_free_mem_region(device, &iomem_resource, - size); - if (IS_ERR(devmem->resource)) - return ERR_CAST(devmem->resource); - devmem->pfn_first = devmem->resource->start >> PAGE_SHIFT; - devmem->pfn_last = devmem->pfn_first + - (resource_size(devmem->resource) >> PAGE_SHIFT); - - devmem->pagemap.type = MEMORY_DEVICE_PRIVATE; - devmem->pagemap.res = *devmem->resource; - devmem->pagemap.ops = &hmm_pagemap_ops; - devmem->pagemap.ref = &devmem->ref; - - result = devm_memremap_pages(devmem->device, &devmem->pagemap); - if (IS_ERR(result)) - return result; - return devmem; -} -EXPORT_SYMBOL_GPL(hmm_devmem_add); -#endif /* CONFIG_DEVICE_PRIVATE */ -- cgit v1.2.3