include/linux/hmm.h - SHIFTPHONES/kernel/shift/mainline - Gitiles

 /* SPDX-License-Identifier: GPL-2.0-or-later */
 /*
  * 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.
  */
 #ifndef LINUX_HMM_H
 #define LINUX_HMM_H

 #include <linux/kconfig.h>
 #include <asm/pgtable.h>

 #include <linux/device.h>
 #include <linux/migrate.h>
 #include <linux/memremap.h>
 #include <linux/completion.h>
 #include <linux/mmu_notifier.h>

 /*
  * 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.
  */
 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 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 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
  */
 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
  *
  * @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, ...)
  * @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 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;
 };

 /*
  * 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.
  */
 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);

 long hmm_range_dma_map(struct hmm_range *range,
 		       struct device *device,
 		       dma_addr_t *daddrs,
 		       unsigned int flags);
 long hmm_range_dma_unmap(struct hmm_range *range,
 			 struct device *device,
 			 dma_addr_t *daddrs,
 			 bool dirty);
 #else
 static inline long hmm_range_fault(struct hmm_range *range, unsigned int flags)
 {
 	return -EOPNOTSUPP;
 }

 static inline long hmm_range_dma_map(struct hmm_range *range,
 				     struct device *device, dma_addr_t *daddrs,
 				     unsigned int flags)
 {
 	return -EOPNOTSUPP;
 }

 static inline long hmm_range_dma_unmap(struct hmm_range *range,
 				       struct device *device,
 				       dma_addr_t *daddrs, bool dirty)
 {
 	return -EOPNOTSUPP;
 }
 #endif

 /*
  * 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

 #endif /* LINUX_HMM_H */
	/* SPDX-License-Identifier: GPL-2.0-or-later */
	/*
	* 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.
	*/
	#ifndef LINUX_HMM_H
	#define LINUX_HMM_H

	#include <linux/kconfig.h>
	#include <asm/pgtable.h>

	#include <linux/device.h>
	#include <linux/migrate.h>
	#include <linux/memremap.h>
	#include <linux/completion.h>
	#include <linux/mmu_notifier.h>

	/*
	* 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.
	*/
	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 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 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
	*/
	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
	*
	* @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, ...)
	* @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 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;
	};

	/*
	* 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.
	*/
	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);

	long hmm_range_dma_map(struct hmm_range *range,
	struct device *device,
	dma_addr_t *daddrs,
	unsigned int flags);
	long hmm_range_dma_unmap(struct hmm_range *range,
	struct device *device,
	dma_addr_t *daddrs,
	bool dirty);
	#else
	static inline long hmm_range_fault(struct hmm_range *range, unsigned int flags)
	{
	return -EOPNOTSUPP;
	}

	static inline long hmm_range_dma_map(struct hmm_range *range,
	struct device device, dma_addr_t daddrs,
	unsigned int flags)
	{
	return -EOPNOTSUPP;
	}

	static inline long hmm_range_dma_unmap(struct hmm_range *range,
	struct device *device,
	dma_addr_t *daddrs, bool dirty)
	{
	return -EOPNOTSUPP;
	}
	#endif

	/*
	* 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

	#endif /* LINUX_HMM_H */