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/* SPDX-License-Identifier: GPL-2.0-or-later */
/*
* Copyright 2013 Red Hat Inc.
*
* Authors: Jérôme Glisse <jglisse@redhat.com>
*
* See Documentation/mm/hmm.rst for reasons and overview of what HMM is.
*/
#ifndef LINUX_HMM_H
#define LINUX_HMM_H
#include <linux/mm.h>
struct mmu_interval_notifier;
/*
* 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_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_to_page() - return struct page pointed to by a device entry
*
* 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 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()
* @start: range virtual start address (inclusive)
* @end: range virtual end address (exclusive)
* @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
* @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;
unsigned long *hmm_pfns;
unsigned long default_flags;
unsigned long pfn_flags_mask;
void *dev_private_owner;
};
/*
* Please see Documentation/mm/hmm.rst for how to use the range API.
*/
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 potentially wait for ever, 1000ms ie 1s sounds like a long time to
* wait already.
*/
#define HMM_RANGE_DEFAULT_TIMEOUT 1000
#endif /* LINUX_HMM_H */