| /* |
| * 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.txt 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> |
| |
| #if IS_ENABLED(CONFIG_HMM) |
| |
| #include <linux/device.h> |
| #include <linux/migrate.h> |
| #include <linux/memremap.h> |
| #include <linux/completion.h> |
| |
| struct hmm; |
| |
| /* |
| * hmm_pfn_t - HMM uses its own pfn type to keep several flags per page |
| * |
| * Flags: |
| * HMM_PFN_VALID: pfn is valid |
| * HMM_PFN_READ: CPU page table has read permission set |
| * HMM_PFN_WRITE: CPU page table has write permission set |
| * HMM_PFN_ERROR: corresponding CPU page table entry points to poisoned memory |
| * HMM_PFN_EMPTY: corresponding CPU page table entry is pte_none() |
| * HMM_PFN_SPECIAL: corresponding CPU page table entry is special; i.e., the |
| * result of vm_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. |
| * HMM_PFN_DEVICE_UNADDRESSABLE: unaddressable device memory (ZONE_DEVICE) |
| */ |
| typedef unsigned long hmm_pfn_t; |
| |
| #define HMM_PFN_VALID (1 << 0) |
| #define HMM_PFN_READ (1 << 1) |
| #define HMM_PFN_WRITE (1 << 2) |
| #define HMM_PFN_ERROR (1 << 3) |
| #define HMM_PFN_EMPTY (1 << 4) |
| #define HMM_PFN_SPECIAL (1 << 5) |
| #define HMM_PFN_DEVICE_UNADDRESSABLE (1 << 6) |
| #define HMM_PFN_SHIFT 7 |
| |
| /* |
| * hmm_pfn_t_to_page() - return struct page pointed to by a valid hmm_pfn_t |
| * @pfn: hmm_pfn_t to convert to struct page |
| * Returns: struct page pointer if pfn is a valid hmm_pfn_t, NULL otherwise |
| * |
| * If the hmm_pfn_t is valid (ie valid flag set) then return the struct page |
| * matching the pfn value stored in the hmm_pfn_t. Otherwise return NULL. |
| */ |
| static inline struct page *hmm_pfn_t_to_page(hmm_pfn_t pfn) |
| { |
| if (!(pfn & HMM_PFN_VALID)) |
| return NULL; |
| return pfn_to_page(pfn >> HMM_PFN_SHIFT); |
| } |
| |
| /* |
| * hmm_pfn_t_to_pfn() - return pfn value store in a hmm_pfn_t |
| * @pfn: hmm_pfn_t to extract pfn from |
| * Returns: pfn value if hmm_pfn_t is valid, -1UL otherwise |
| */ |
| static inline unsigned long hmm_pfn_t_to_pfn(hmm_pfn_t pfn) |
| { |
| if (!(pfn & HMM_PFN_VALID)) |
| return -1UL; |
| return (pfn >> HMM_PFN_SHIFT); |
| } |
| |
| /* |
| * hmm_pfn_t_from_page() - create a valid hmm_pfn_t value from struct page |
| * @page: struct page pointer for which to create the hmm_pfn_t |
| * Returns: valid hmm_pfn_t for the page |
| */ |
| static inline hmm_pfn_t hmm_pfn_t_from_page(struct page *page) |
| { |
| return (page_to_pfn(page) << HMM_PFN_SHIFT) | HMM_PFN_VALID; |
| } |
| |
| /* |
| * hmm_pfn_t_from_pfn() - create a valid hmm_pfn_t value from pfn |
| * @pfn: pfn value for which to create the hmm_pfn_t |
| * Returns: valid hmm_pfn_t for the pfn |
| */ |
| static inline hmm_pfn_t hmm_pfn_t_from_pfn(unsigned long pfn) |
| { |
| return (pfn << HMM_PFN_SHIFT) | 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_type - type of update |
| * @HMM_UPDATE_INVALIDATE: invalidate range (no indication as to why) |
| */ |
| enum hmm_update_type { |
| HMM_UPDATE_INVALIDATE, |
| }; |
| |
| /* |
| * struct hmm_mirror_ops - HMM mirror device operations callback |
| * |
| * @update: callback to update range on a device |
| */ |
| struct hmm_mirror_ops { |
| /* 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 |
| * |
| * 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. |
| */ |
| void (*sync_cpu_device_pagetables)(struct hmm_mirror *mirror, |
| enum hmm_update_type update_type, |
| unsigned long start, |
| unsigned long end); |
| }; |
| |
| /* |
| * 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); |
| |
| |
| /* |
| * struct hmm_range - track invalidation lock on virtual address 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) |
| * @valid: pfns array did not change since it has been fill by an HMM function |
| */ |
| struct hmm_range { |
| struct list_head list; |
| unsigned long start; |
| unsigned long end; |
| hmm_pfn_t *pfns; |
| bool valid; |
| }; |
| |
| /* |
| * To snapshot the CPU page table, call hmm_vma_get_pfns(), then take a device |
| * driver lock that serializes device page table updates, then call |
| * hmm_vma_range_done(), to check if the snapshot is still valid. The same |
| * device driver page table update lock must also be used in the |
| * hmm_mirror_ops.sync_cpu_device_pagetables() callback, so that CPU page |
| * table invalidation serializes on it. |
| * |
| * YOU MUST CALL hmm_vma_range_done() ONCE AND ONLY ONCE EACH TIME YOU CALL |
| * hmm_vma_get_pfns() WITHOUT ERROR ! |
| * |
| * IF YOU DO NOT FOLLOW THE ABOVE RULE THE SNAPSHOT CONTENT MIGHT BE INVALID ! |
| */ |
| int hmm_vma_get_pfns(struct vm_area_struct *vma, |
| struct hmm_range *range, |
| unsigned long start, |
| unsigned long end, |
| hmm_pfn_t *pfns); |
| bool hmm_vma_range_done(struct vm_area_struct *vma, struct hmm_range *range); |
| |
| |
| /* |
| * Fault memory on behalf of device driver. Unlike handle_mm_fault(), this will |
| * not migrate any device memory back to system memory. The hmm_pfn_t array will |
| * be updated with the fault result and current snapshot of the CPU page table |
| * for the range. |
| * |
| * The mmap_sem must be taken in read mode before entering and it might be |
| * dropped by the function if the block argument is false. In that case, the |
| * function returns -EAGAIN. |
| * |
| * Return value does not reflect if the fault was successful for every single |
| * address or not. Therefore, the caller must to inspect the hmm_pfn_t array to |
| * determine fault status for each address. |
| * |
| * Trying to fault inside an invalid vma will result in -EINVAL. |
| * |
| * See the function description in mm/hmm.c for further documentation. |
| */ |
| int hmm_vma_fault(struct vm_area_struct *vma, |
| struct hmm_range *range, |
| unsigned long start, |
| unsigned long end, |
| hmm_pfn_t *pfns, |
| bool write, |
| bool block); |
| #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. |
| */ |
| int (*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 |
| * |
| * 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. |
| */ |
| 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. The device driver must call hmm_devmem_remove() before the |
| * device goes away and before freeing the hmm_devmem struct memory. |
| */ |
| 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); |
| |
| /* |
| * 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) |
| { |
| unsigned long *drvdata = (unsigned long *)&page->pgmap; |
| |
| drvdata[1] = 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(struct page *page) |
| { |
| unsigned long *drvdata = (unsigned long *)&page->pgmap; |
| |
| return drvdata[1]; |
| } |
| |
| |
| /* |
| * 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 */ |
| |
| |
| /* 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) */ |
| |
| /* Below are for HMM internal use only! Not to be used by device driver! */ |
| 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 */ |