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Diffstat (limited to 'include/linux/hmm.h')
| -rw-r--r-- | include/linux/hmm.h | 267 |
1 files changed, 67 insertions, 200 deletions
diff --git a/include/linux/hmm.h b/include/linux/hmm.h index ddf9f7144c43..126a36571667 100644 --- a/include/linux/hmm.h +++ b/include/linux/hmm.h @@ -3,245 +3,112 @@ * Copyright 2013 Red Hat Inc. * * 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 a range of the CPU - * page tables 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. + * See Documentation/mm/hmm.rst for reasons and overview of what HMM is. */ #ifndef LINUX_HMM_H #define LINUX_HMM_H -#include <linux/kconfig.h> -#include <asm/pgtable.h> +#include <linux/mm.h> -#include <linux/device.h> -#include <linux/migrate.h> -#include <linux/memremap.h> -#include <linux/completion.h> -#include <linux/mmu_notifier.h> +struct mmu_interval_notifier; /* - * 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 provides a flags array for mapping page protections to device - * PTE bits. If the driver valid bit for an entry is bit 3, - * i.e., (entry & (1 << 3)), then the 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 the same idea as vm_page_prot in vma - * except that this is per device driver rather than per architecture. + * On output: + * 0 - The page is faultable and a future call with + * HMM_PFN_REQ_FAULT could succeed. + * HMM_PFN_VALID - the pfn field points to a valid PFN. This PFN is at + * least readable. If dev_private_owner is !NULL then this could + * point at a DEVICE_PRIVATE page. + * HMM_PFN_WRITE - if the page memory can be written to (requires HMM_PFN_VALID) + * HMM_PFN_ERROR - accessing the pfn is impossible and the device should + * fail. ie poisoned memory, special pages, no vma, etc + * + * On input: + * 0 - Return the current state of the page, do not fault it. + * HMM_PFN_REQ_FAULT - The output must have HMM_PFN_VALID or hmm_range_fault() + * will fail + * HMM_PFN_REQ_WRITE - The output must have HMM_PFN_WRITE or hmm_range_fault() + * will fail. Must be combined with HMM_PFN_REQ_FAULT. */ -enum hmm_pfn_flag_e { - HMM_PFN_VALID = 0, - HMM_PFN_WRITE, - HMM_PFN_DEVICE_PRIVATE, - HMM_PFN_FLAG_MAX +enum hmm_pfn_flags { + /* Output fields and flags */ + HMM_PFN_VALID = 1UL << (BITS_PER_LONG - 1), + HMM_PFN_WRITE = 1UL << (BITS_PER_LONG - 2), + HMM_PFN_ERROR = 1UL << (BITS_PER_LONG - 3), + HMM_PFN_ORDER_SHIFT = (BITS_PER_LONG - 8), + + /* Input flags */ + HMM_PFN_REQ_FAULT = HMM_PFN_VALID, + HMM_PFN_REQ_WRITE = HMM_PFN_WRITE, + + HMM_PFN_FLAGS = 0xFFUL << HMM_PFN_ORDER_SHIFT, }; /* - * 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 provides values for none entry, error entry, and special entry. - * Driver can alias (i.e., use same value) error and special, but - * it should not alias none with error or special. + * hmm_pfn_to_page() - return struct page pointed to by a device entry * - * 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 entry, - * hmm_range.values[HMM_PFN_SPECIAL] if CPU page table entry is a special one + * This must be called under the caller 'user_lock' after a successful + * mmu_interval_read_begin(). The caller must have tested for HMM_PFN_VALID + * already. */ -enum hmm_pfn_value_e { - HMM_PFN_ERROR, - HMM_PFN_NONE, - HMM_PFN_SPECIAL, - HMM_PFN_VALUE_MAX -}; +static inline struct page *hmm_pfn_to_page(unsigned long hmm_pfn) +{ + return pfn_to_page(hmm_pfn & ~HMM_PFN_FLAGS); +} + +/* + * hmm_pfn_to_map_order() - return the CPU mapping size order + * + * This is optionally useful to optimize processing of the pfn result + * array. It indicates that the page starts at the order aligned VA and is + * 1<<order bytes long. Every pfn within an high order page will have the + * same pfn flags, both access protections and the map_order. The caller must + * be careful with edge cases as the start and end VA of the given page may + * extend past the range used with hmm_range_fault(). + * + * This must be called under the caller 'user_lock' after a successful + * mmu_interval_read_begin(). The caller must have tested for HMM_PFN_VALID + * already. + */ +static inline unsigned int hmm_pfn_to_map_order(unsigned long hmm_pfn) +{ + return (hmm_pfn >> HMM_PFN_ORDER_SHIFT) & 0x1F; +} /* * struct hmm_range - track invalidation lock on virtual address range * * @notifier: a mmu_interval_notifier that includes the start/end * @notifier_seq: result of mmu_interval_read_begin() - * @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, ...) + * @hmm_pfns: array of pfns (big enough for the range) * @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 + * @dev_private_owner: owner of device private pages */ struct hmm_range { struct mmu_interval_notifier *notifier; unsigned long notifier_seq; 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 pfn_shift; + unsigned long *hmm_pfns; + unsigned long default_flags; + unsigned long pfn_flags_mask; + void *dev_private_owner; }; /* - * hmm_device_entry_to_page() - return struct page pointed to by a device entry - * @range: range use to decode device entry value - * @entry: device entry value to get corresponding struct page from - * Return: struct page pointer if entry is a valid, NULL otherwise - * - * If the device entry is valid (ie valid flag set) then return the struct page - * matching the entry value. Otherwise return NULL. + * Please see Documentation/mm/hmm.rst for how to use the range API. */ -static inline struct page *hmm_device_entry_to_page(const struct hmm_range *range, - uint64_t entry) -{ - if (entry == range->values[HMM_PFN_NONE]) - return NULL; - if (entry == range->values[HMM_PFN_ERROR]) - return NULL; - if (entry == range->values[HMM_PFN_SPECIAL]) - return NULL; - if (!(entry & range->flags[HMM_PFN_VALID])) - return NULL; - return pfn_to_page(entry >> range->pfn_shift); -} - -/* - * hmm_device_entry_to_pfn() - return pfn value store in a device entry - * @range: range use to decode device entry value - * @entry: device entry to extract pfn from - * Return: pfn value if device entry is valid, -1UL otherwise - */ -static inline unsigned long -hmm_device_entry_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_device_entry_from_page() - create a valid device entry for a page - * @range: range use to encode HMM pfn value - * @page: page for which to create the device entry - * Return: valid device entry for the page - */ -static inline uint64_t hmm_device_entry_from_page(const struct hmm_range *range, - struct page *page) -{ - return (page_to_pfn(page) << range->pfn_shift) | - range->flags[HMM_PFN_VALID]; -} - -/* - * hmm_device_entry_from_pfn() - create a valid device entry value from pfn - * @range: range use to encode HMM pfn value - * @pfn: pfn value for which to create the device entry - * Return: valid device entry for the pfn - */ -static inline uint64_t hmm_device_entry_from_pfn(const struct hmm_range *range, - unsigned long pfn) -{ - return (pfn << range->pfn_shift) | - range->flags[HMM_PFN_VALID]; -} - -/* - * Retry fault if non-blocking, drop mmap_sem and return -EAGAIN in that case. - */ -#define HMM_FAULT_ALLOW_RETRY (1 << 0) - -/* Don't fault in missing PTEs, just snapshot the current state. */ -#define HMM_FAULT_SNAPSHOT (1 << 1) - -#ifdef CONFIG_HMM_MIRROR -/* - * Please see Documentation/vm/hmm.rst for how to use the range API. - */ -long hmm_range_fault(struct hmm_range *range, unsigned int flags); -#else -static inline long hmm_range_fault(struct hmm_range *range, unsigned int flags) -{ - return -EOPNOTSUPP; -} -#endif +int hmm_range_fault(struct hmm_range *range); /* * 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 + * could potentially wait for ever, 1000ms ie 1s sounds like a long time to * wait already. */ #define HMM_RANGE_DEFAULT_TIMEOUT 1000 |