Commit 997308f9 authored by Paolo Bonzini's avatar Paolo Bonzini
Browse files

mmu_notifier: remove the .change_pte() callback 



The scope of set_pte_at_notify() has reduced more and more through the
years.  Initially, it was meant for when the change to the PTE was
not bracketed by mmu_notifier_invalidate_range_{start,end}().  However,
that has not been so for over ten years.  During all this period
the only implementation of .change_pte() was KVM and it
had no actual functionality, because it was called after
mmu_notifier_invalidate_range_start() zapped the secondary PTE.

Now that this (nonfunctional) user of the .change_pte() callback is
gone, the whole callback can be removed.  For now, leave in place
set_pte_at_notify() even though it is just a synonym for set_pte_at().

Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Reviewed-by: default avatarDavid Hildenbrand <david@redhat.com>
Message-ID: <20240405115815.3226315-4-pbonzini@redhat.com>
Acked-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 5257de95

include/linux/mmu_notifier.h

+2 −44
Original line number Diff line number Diff line
@@ -122,15 +122,6 @@ struct mmu_notifier_ops { 
			  struct mm_struct *mm,

			  unsigned long address);



	/*

	 * change_pte is called in cases that pte mapping to page is changed:

	 * for example, when ksm remaps pte to point to a new shared page.

	 */

	void (*change_pte)(struct mmu_notifier *subscription,

			   struct mm_struct *mm,

			   unsigned long address,

			   pte_t pte);



	/*

	 * invalidate_range_start() and invalidate_range_end() must be

	 * paired and are called only when the mmap_lock and/or the
@@ -392,8 +383,6 @@ extern int __mmu_notifier_clear_young(struct mm_struct *mm, 
				      unsigned long end);

extern int __mmu_notifier_test_young(struct mm_struct *mm,

				     unsigned long address);

extern void __mmu_notifier_change_pte(struct mm_struct *mm,

				      unsigned long address, pte_t pte);

extern int __mmu_notifier_invalidate_range_start(struct mmu_notifier_range *r);

extern void __mmu_notifier_invalidate_range_end(struct mmu_notifier_range *r);

extern void __mmu_notifier_arch_invalidate_secondary_tlbs(struct mm_struct *mm,
@@ -439,13 +428,6 @@ static inline int mmu_notifier_test_young(struct mm_struct *mm, 
	return 0;

}



static inline void mmu_notifier_change_pte(struct mm_struct *mm,

					   unsigned long address, pte_t pte)

{

	if (mm_has_notifiers(mm))

		__mmu_notifier_change_pte(mm, address, pte);

}



static inline void

mmu_notifier_invalidate_range_start(struct mmu_notifier_range *range)

{
@@ -581,26 +563,6 @@ static inline void mmu_notifier_range_init_owner( 
	__young;							\

})



/*

 * set_pte_at_notify() sets the pte _after_ running the notifier.

 * This is safe to start by updating the secondary MMUs, because the primary MMU

 * pte invalidate must have already happened with a ptep_clear_flush() before

 * set_pte_at_notify() has been invoked.  Updating the secondary MMUs first is

 * required when we change both the protection of the mapping from read-only to

 * read-write and the pfn (like during copy on write page faults). Otherwise the

 * old page would remain mapped readonly in the secondary MMUs after the new

 * page is already writable by some CPU through the primary MMU.

 */

#define set_pte_at_notify(__mm, __address, __ptep, __pte)		\

({									\

	struct mm_struct *___mm = __mm;					\

	unsigned long ___address = __address;				\

	pte_t ___pte = __pte;						\

									\

	mmu_notifier_change_pte(___mm, ___address, ___pte);		\

	set_pte_at(___mm, ___address, __ptep, ___pte);			\

})



#else /* CONFIG_MMU_NOTIFIER */



struct mmu_notifier_range {
@@ -650,11 +612,6 @@ static inline int mmu_notifier_test_young(struct mm_struct *mm, 
	return 0;

}



static inline void mmu_notifier_change_pte(struct mm_struct *mm,

					   unsigned long address, pte_t pte)

{

}



static inline void

mmu_notifier_invalidate_range_start(struct mmu_notifier_range *range)

{
@@ -693,7 +650,6 @@ static inline void mmu_notifier_subscriptions_destroy(struct mm_struct *mm) 
#define	ptep_clear_flush_notify ptep_clear_flush

#define pmdp_huge_clear_flush_notify pmdp_huge_clear_flush

#define pudp_huge_clear_flush_notify pudp_huge_clear_flush

#define set_pte_at_notify set_pte_at



static inline void mmu_notifier_synchronize(void)

{
@@ -701,4 +657,6 @@ static inline void mmu_notifier_synchronize(void) 


#endif /* CONFIG_MMU_NOTIFIER */



#define set_pte_at_notify set_pte_at



#endif /* _LINUX_MMU_NOTIFIER_H */

mm/mmu_notifier.c

+0 −17
Original line number Diff line number Diff line
@@ -424,23 +424,6 @@ int __mmu_notifier_test_young(struct mm_struct *mm, 
	return young;

}



void __mmu_notifier_change_pte(struct mm_struct *mm, unsigned long address,

			       pte_t pte)

{

	struct mmu_notifier *subscription;

	int id;



	id = srcu_read_lock(&srcu);

	hlist_for_each_entry_rcu(subscription,

				 &mm->notifier_subscriptions->list, hlist,

				 srcu_read_lock_held(&srcu)) {

		if (subscription->ops->change_pte)

			subscription->ops->change_pte(subscription, mm, address,

						      pte);

	}

	srcu_read_unlock(&srcu, id);

}



static int mn_itree_invalidate(struct mmu_notifier_subscriptions *subscriptions,

			       const struct mmu_notifier_range *range)

{