/** * enum mmu_notifier_event - reason for the mmu notifier callback * @MMU_NOTIFY_UNMAP: either munmap() that unmap the range or a mremap() that * move the range * * @MMU_NOTIFY_CLEAR: clear page table entry (many reasons for this like * madvise() or replacing a page by another one, ...). * * @MMU_NOTIFY_PROTECTION_VMA: update is due to protection change for the range * ie using the vma access permission (vm_page_prot) to update the whole range * is enough no need to inspect changes to the CPU page table (mprotect() * syscall) * * @MMU_NOTIFY_PROTECTION_PAGE: update is due to change in read/write flag for * pages in the range so to mirror those changes the user must inspect the CPU * page table (from the end callback). * * @MMU_NOTIFY_SOFT_DIRTY: soft dirty accounting (still same page and same * access flags). User should soft dirty the page in the end callback to make * sure that anyone relying on soft dirtiness catch pages that might be written * through non CPU mappings. * * @MMU_NOTIFY_RELEASE: used during mmu_interval_notifier invalidate to signal * that the mm refcount is zero and the range is no longer accessible. * * @MMU_NOTIFY_MIGRATE: used during migrate_vma_collect() invalidate to signal * a device driver to possibly ignore the invalidation if the * owner field matches the driver's device private pgmap owner. * * @MMU_NOTIFY_EXCLUSIVE: conversion of a page table entry to device-exclusive. * The owner is initialized to the value provided by the caller of * make_device_exclusive(), such that this caller can filter out these * events.
*/ enum mmu_notifier_event {
MMU_NOTIFY_UNMAP = 0,
MMU_NOTIFY_CLEAR,
MMU_NOTIFY_PROTECTION_VMA,
MMU_NOTIFY_PROTECTION_PAGE,
MMU_NOTIFY_SOFT_DIRTY,
MMU_NOTIFY_RELEASE,
MMU_NOTIFY_MIGRATE,
MMU_NOTIFY_EXCLUSIVE,
};
#define MMU_NOTIFIER_RANGE_BLOCKABLE (1 << 0)
struct mmu_notifier_ops { /* * Called either by mmu_notifier_unregister or when the mm is * being destroyed by exit_mmap, always before all pages are * freed. This can run concurrently with other mmu notifier * methods (the ones invoked outside the mm context) and it * should tear down all secondary mmu mappings and freeze the * secondary mmu. If this method isn't implemented you've to * be sure that nothing could possibly write to the pages * through the secondary mmu by the time the last thread with * tsk->mm == mm exits. * * As side note: the pages freed after ->release returns could * be immediately reallocated by the gart at an alias physical * address with a different cache model, so if ->release isn't * implemented because all _software_ driven memory accesses * through the secondary mmu are terminated by the time the * last thread of this mm quits, you've also to be sure that * speculative _hardware_ operations can't allocate dirty * cachelines in the cpu that could not be snooped and made * coherent with the other read and write operations happening * through the gart alias address, so leading to memory * corruption.
*/ void (*release)(struct mmu_notifier *subscription, struct mm_struct *mm);
/* * clear_flush_young is called after the VM is * test-and-clearing the young/accessed bitflag in the * pte. This way the VM will provide proper aging to the * accesses to the page through the secondary MMUs and not * only to the ones through the Linux pte. * Start-end is necessary in case the secondary MMU is mapping the page * at a smaller granularity than the primary MMU.
*/ int (*clear_flush_young)(struct mmu_notifier *subscription, struct mm_struct *mm, unsignedlong start, unsignedlong end);
/* * clear_young is a lightweight version of clear_flush_young. Like the * latter, it is supposed to test-and-clear the young/accessed bitflag * in the secondary pte, but it may omit flushing the secondary tlb.
*/ int (*clear_young)(struct mmu_notifier *subscription, struct mm_struct *mm, unsignedlong start, unsignedlong end);
/* * test_young is called to check the young/accessed bitflag in * the secondary pte. This is used to know if the page is * frequently used without actually clearing the flag or tearing * down the secondary mapping on the page.
*/ int (*test_young)(struct mmu_notifier *subscription, struct mm_struct *mm, unsignedlong address);
/* * invalidate_range_start() and invalidate_range_end() must be * paired and are called only when the mmap_lock and/or the * locks protecting the reverse maps are held. If the subsystem * can't guarantee that no additional references are taken to * the pages in the range, it has to implement the * invalidate_range() notifier to remove any references taken * after invalidate_range_start(). * * Invalidation of multiple concurrent ranges may be * optionally permitted by the driver. Either way the * establishment of sptes is forbidden in the range passed to * invalidate_range_begin/end for the whole duration of the * invalidate_range_begin/end critical section. * * invalidate_range_start() is called when all pages in the * range are still mapped and have at least a refcount of one. * * invalidate_range_end() is called when all pages in the * range have been unmapped and the pages have been freed by * the VM. * * The VM will remove the page table entries and potentially * the page between invalidate_range_start() and * invalidate_range_end(). If the page must not be freed * because of pending I/O or other circumstances then the * invalidate_range_start() callback (or the initial mapping * by the driver) must make sure that the refcount is kept * elevated. * * If the driver increases the refcount when the pages are * initially mapped into an address space then either * invalidate_range_start() or invalidate_range_end() may * decrease the refcount. If the refcount is decreased on * invalidate_range_start() then the VM can free pages as page * table entries are removed. If the refcount is only * dropped on invalidate_range_end() then the driver itself * will drop the last refcount but it must take care to flush * any secondary tlb before doing the final free on the * page. Pages will no longer be referenced by the linux * address space but may still be referenced by sptes until * the last refcount is dropped. * * If blockable argument is set to false then the callback cannot * sleep and has to return with -EAGAIN if sleeping would be required. * 0 should be returned otherwise. Please note that notifiers that can * fail invalidate_range_start are not allowed to implement * invalidate_range_end, as there is no mechanism for informing the * notifier that its start failed.
*/ int (*invalidate_range_start)(struct mmu_notifier *subscription, conststruct mmu_notifier_range *range); void (*invalidate_range_end)(struct mmu_notifier *subscription, conststruct mmu_notifier_range *range);
/* * arch_invalidate_secondary_tlbs() is used to manage a non-CPU TLB * which shares page-tables with the CPU. The * invalidate_range_start()/end() callbacks should not be implemented as * invalidate_secondary_tlbs() already catches the points in time when * an external TLB needs to be flushed. * * This requires arch_invalidate_secondary_tlbs() to be called while * holding the ptl spin-lock and therefore this callback is not allowed * to sleep. * * This is called by architecture code whenever invalidating a TLB * entry. It is assumed that any secondary TLB has the same rules for * when invalidations are required. If this is not the case architecture * code will need to call this explicitly when required for secondary * TLB invalidation.
*/ void (*arch_invalidate_secondary_tlbs)( struct mmu_notifier *subscription, struct mm_struct *mm, unsignedlong start, unsignedlong end);
/* * These callbacks are used with the get/put interface to manage the * lifetime of the mmu_notifier memory. alloc_notifier() returns a new * notifier for use with the mm. * * free_notifier() is only called after the mmu_notifier has been * fully put, calls to any ops callback are prevented and no ops * callbacks are currently running. It is called from a SRCU callback * and cannot sleep.
*/ struct mmu_notifier *(*alloc_notifier)(struct mm_struct *mm); void (*free_notifier)(struct mmu_notifier *subscription);
};
/* * The notifier chains are protected by mmap_lock and/or the reverse map * semaphores. Notifier chains are only changed when all reverse maps and * the mmap_lock locks are taken. * * Therefore notifier chains can only be traversed when either * * 1. mmap_lock is held. * 2. One of the reverse map locks is held (i_mmap_rwsem or anon_vma->rwsem). * 3. No other concurrent thread can access the list (release)
*/ struct mmu_notifier { struct hlist_node hlist; conststruct mmu_notifier_ops *ops; struct mm_struct *mm; struct rcu_head rcu; unsignedint users;
};
/** * struct mmu_interval_notifier_ops * @invalidate: Upon return the caller must stop using any SPTEs within this * range. This function can sleep. Return false only if sleeping * was required but mmu_notifier_range_blockable(range) is false.
*/ struct mmu_interval_notifier_ops { bool (*invalidate)(struct mmu_interval_notifier *interval_sub, conststruct mmu_notifier_range *range, unsignedlong cur_seq);
};
/** * mmu_interval_set_seq - Save the invalidation sequence * @interval_sub - The subscription passed to invalidate * @cur_seq - The cur_seq passed to the invalidate() callback * * This must be called unconditionally from the invalidate callback of a * struct mmu_interval_notifier_ops under the same lock that is used to call * mmu_interval_read_retry(). It updates the sequence number for later use by * mmu_interval_read_retry(). The provided cur_seq will always be odd. * * If the caller does not call mmu_interval_read_begin() or * mmu_interval_read_retry() then this call is not required.
*/ staticinlinevoid
mmu_interval_set_seq(struct mmu_interval_notifier *interval_sub, unsignedlong cur_seq)
{
WRITE_ONCE(interval_sub->invalidate_seq, cur_seq);
}
/** * mmu_interval_read_retry - End a read side critical section against a VA range * interval_sub: The subscription * seq: The return of the paired mmu_interval_read_begin() * * This MUST be called under a user provided lock that is also held * unconditionally by op->invalidate() when it calls mmu_interval_set_seq(). * * Each call should be paired with a single mmu_interval_read_begin() and * should be used to conclude the read side. * * Returns true if an invalidation collided with this critical section, and * the caller should retry.
*/ staticinlinebool
mmu_interval_read_retry(struct mmu_interval_notifier *interval_sub, unsignedlong seq)
{ return interval_sub->invalidate_seq != seq;
}
/** * mmu_interval_check_retry - Test if a collision has occurred * interval_sub: The subscription * seq: The return of the matching mmu_interval_read_begin() * * This can be used in the critical section between mmu_interval_read_begin() * and mmu_interval_read_retry(). A return of true indicates an invalidation * has collided with this critical region and a future * mmu_interval_read_retry() will return true. * * False is not reliable and only suggests a collision may not have * occurred. It can be called many times and does not have to hold the user * provided lock. * * This call can be used as part of loops and other expensive operations to * expedite a retry.
*/ staticinlinebool
mmu_interval_check_retry(struct mmu_interval_notifier *interval_sub, unsignedlong seq)
{ /* Pairs with the WRITE_ONCE in mmu_interval_set_seq() */ return READ_ONCE(interval_sub->invalidate_seq) != seq;
}
/* * This version of mmu_notifier_invalidate_range_start() avoids blocking, but it * can return an error if a notifier can't proceed without blocking, in which * case you're not allowed to modify PTEs in the specified range. * * This is mainly intended for OOM handling.
*/ staticinlineint __must_check
mmu_notifier_invalidate_range_start_nonblock(struct mmu_notifier_range *range)
{ int ret = 0;
lock_map_acquire(&__mmu_notifier_invalidate_range_start_map); if (mm_has_notifiers(range->mm)) {
range->flags &= ~MMU_NOTIFIER_RANGE_BLOCKABLE;
ret = __mmu_notifier_invalidate_range_start(range);
}
lock_map_release(&__mmu_notifier_invalidate_range_start_map); return ret;
}
staticinlinevoid
mmu_notifier_invalidate_range_end(struct mmu_notifier_range *range)
{ if (mmu_notifier_range_blockable(range))
might_sleep();
if (mm_has_notifiers(range->mm))
__mmu_notifier_invalidate_range_end(range);
}
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