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mmu_notifier: remove the .change_pte() callback

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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: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Message-ID: <20240405115815.3226315-4-pbonzini@redhat.com>
Acked-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2024-04-05 07:58:14 -04:00
parent 5257de954c
commit 997308f9ae
2 changed files with 2 additions and 61 deletions
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46
include/linux/mmu_notifier.h
View File

@ -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 */

17
mm/mmu_notifier.c
View File

@ -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)
{