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8ee53820ed
For GRU and EPT, we need gup-fast to set referenced bit too (this is why it's correct to return 0 when shadow_access_mask is zero, it requires gup-fast to set the referenced bit). qemu-kvm access already sets the young bit in the pte if it isn't zero-copy, if it's zero copy or a shadow paging EPT minor fault we relay on gup-fast to signal the page is in use... We also need to check the young bits on the secondary pagetables for NPT and not nested shadow mmu as the data may never get accessed again by the primary pte. Without this closer accuracy, we'd have to remove the heuristic that avoids collapsing hugepages in hugepage virtual regions that have not even a single subpage in use. ->test_young is full backwards compatible with GRU and other usages that don't have young bits in pagetables set by the hardware and that should nuke the secondary mmu mappings when ->clear_flush_young runs just like EPT does. Removing the heuristic that checks the young bit in khugepaged/collapse_huge_page completely isn't so bad either probably but I thought it was worth it and this makes it reliable. Signed-off-by: Andrea Arcangeli <aarcange@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
380 lines
12 KiB
C
380 lines
12 KiB
C
#ifndef _LINUX_MMU_NOTIFIER_H
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#define _LINUX_MMU_NOTIFIER_H
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#include <linux/list.h>
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#include <linux/spinlock.h>
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#include <linux/mm_types.h>
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struct mmu_notifier;
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struct mmu_notifier_ops;
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#ifdef CONFIG_MMU_NOTIFIER
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/*
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* The mmu notifier_mm structure is allocated and installed in
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* mm->mmu_notifier_mm inside the mm_take_all_locks() protected
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* critical section and it's released only when mm_count reaches zero
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* in mmdrop().
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*/
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struct mmu_notifier_mm {
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/* all mmu notifiers registerd in this mm are queued in this list */
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struct hlist_head list;
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/* to serialize the list modifications and hlist_unhashed */
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spinlock_t lock;
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};
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struct mmu_notifier_ops {
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/*
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* Called either by mmu_notifier_unregister or when the mm is
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* being destroyed by exit_mmap, always before all pages are
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* freed. This can run concurrently with other mmu notifier
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* methods (the ones invoked outside the mm context) and it
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* should tear down all secondary mmu mappings and freeze the
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* secondary mmu. If this method isn't implemented you've to
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* be sure that nothing could possibly write to the pages
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* through the secondary mmu by the time the last thread with
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* tsk->mm == mm exits.
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*
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* As side note: the pages freed after ->release returns could
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* be immediately reallocated by the gart at an alias physical
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* address with a different cache model, so if ->release isn't
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* implemented because all _software_ driven memory accesses
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* through the secondary mmu are terminated by the time the
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* last thread of this mm quits, you've also to be sure that
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* speculative _hardware_ operations can't allocate dirty
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* cachelines in the cpu that could not be snooped and made
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* coherent with the other read and write operations happening
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* through the gart alias address, so leading to memory
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* corruption.
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*/
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void (*release)(struct mmu_notifier *mn,
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struct mm_struct *mm);
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/*
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* clear_flush_young is called after the VM is
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* test-and-clearing the young/accessed bitflag in the
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* pte. This way the VM will provide proper aging to the
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* accesses to the page through the secondary MMUs and not
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* only to the ones through the Linux pte.
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*/
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int (*clear_flush_young)(struct mmu_notifier *mn,
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struct mm_struct *mm,
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unsigned long address);
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/*
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* test_young is called to check the young/accessed bitflag in
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* the secondary pte. This is used to know if the page is
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* frequently used without actually clearing the flag or tearing
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* down the secondary mapping on the page.
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*/
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int (*test_young)(struct mmu_notifier *mn,
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struct mm_struct *mm,
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unsigned long address);
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/*
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* change_pte is called in cases that pte mapping to page is changed:
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* for example, when ksm remaps pte to point to a new shared page.
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*/
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void (*change_pte)(struct mmu_notifier *mn,
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struct mm_struct *mm,
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unsigned long address,
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pte_t pte);
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/*
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* Before this is invoked any secondary MMU is still ok to
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* read/write to the page previously pointed to by the Linux
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* pte because the page hasn't been freed yet and it won't be
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* freed until this returns. If required set_page_dirty has to
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* be called internally to this method.
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*/
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void (*invalidate_page)(struct mmu_notifier *mn,
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struct mm_struct *mm,
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unsigned long address);
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/*
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* invalidate_range_start() and invalidate_range_end() must be
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* paired and are called only when the mmap_sem and/or the
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* locks protecting the reverse maps are held. The subsystem
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* must guarantee that no additional references are taken to
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* the pages in the range established between the call to
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* invalidate_range_start() and the matching call to
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* invalidate_range_end().
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*
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* Invalidation of multiple concurrent ranges may be
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* optionally permitted by the driver. Either way the
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* establishment of sptes is forbidden in the range passed to
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* invalidate_range_begin/end for the whole duration of the
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* invalidate_range_begin/end critical section.
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*
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* invalidate_range_start() is called when all pages in the
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* range are still mapped and have at least a refcount of one.
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*
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* invalidate_range_end() is called when all pages in the
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* range have been unmapped and the pages have been freed by
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* the VM.
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*
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* The VM will remove the page table entries and potentially
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* the page between invalidate_range_start() and
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* invalidate_range_end(). If the page must not be freed
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* because of pending I/O or other circumstances then the
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* invalidate_range_start() callback (or the initial mapping
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* by the driver) must make sure that the refcount is kept
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* elevated.
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*
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* If the driver increases the refcount when the pages are
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* initially mapped into an address space then either
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* invalidate_range_start() or invalidate_range_end() may
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* decrease the refcount. If the refcount is decreased on
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* invalidate_range_start() then the VM can free pages as page
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* table entries are removed. If the refcount is only
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* droppped on invalidate_range_end() then the driver itself
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* will drop the last refcount but it must take care to flush
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* any secondary tlb before doing the final free on the
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* page. Pages will no longer be referenced by the linux
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* address space but may still be referenced by sptes until
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* the last refcount is dropped.
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*/
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void (*invalidate_range_start)(struct mmu_notifier *mn,
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struct mm_struct *mm,
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unsigned long start, unsigned long end);
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void (*invalidate_range_end)(struct mmu_notifier *mn,
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struct mm_struct *mm,
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unsigned long start, unsigned long end);
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};
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/*
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* The notifier chains are protected by mmap_sem and/or the reverse map
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* semaphores. Notifier chains are only changed when all reverse maps and
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* the mmap_sem locks are taken.
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*
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* Therefore notifier chains can only be traversed when either
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*
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* 1. mmap_sem is held.
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* 2. One of the reverse map locks is held (i_mmap_lock or anon_vma->lock).
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* 3. No other concurrent thread can access the list (release)
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*/
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struct mmu_notifier {
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struct hlist_node hlist;
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const struct mmu_notifier_ops *ops;
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};
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static inline int mm_has_notifiers(struct mm_struct *mm)
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{
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return unlikely(mm->mmu_notifier_mm);
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}
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extern int mmu_notifier_register(struct mmu_notifier *mn,
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struct mm_struct *mm);
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extern int __mmu_notifier_register(struct mmu_notifier *mn,
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struct mm_struct *mm);
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extern void mmu_notifier_unregister(struct mmu_notifier *mn,
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struct mm_struct *mm);
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extern void __mmu_notifier_mm_destroy(struct mm_struct *mm);
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extern void __mmu_notifier_release(struct mm_struct *mm);
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extern int __mmu_notifier_clear_flush_young(struct mm_struct *mm,
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unsigned long address);
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extern int __mmu_notifier_test_young(struct mm_struct *mm,
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unsigned long address);
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extern void __mmu_notifier_change_pte(struct mm_struct *mm,
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unsigned long address, pte_t pte);
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extern void __mmu_notifier_invalidate_page(struct mm_struct *mm,
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unsigned long address);
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extern void __mmu_notifier_invalidate_range_start(struct mm_struct *mm,
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unsigned long start, unsigned long end);
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extern void __mmu_notifier_invalidate_range_end(struct mm_struct *mm,
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unsigned long start, unsigned long end);
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static inline void mmu_notifier_release(struct mm_struct *mm)
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{
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if (mm_has_notifiers(mm))
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__mmu_notifier_release(mm);
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}
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static inline int mmu_notifier_clear_flush_young(struct mm_struct *mm,
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unsigned long address)
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{
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if (mm_has_notifiers(mm))
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return __mmu_notifier_clear_flush_young(mm, address);
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return 0;
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}
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static inline int mmu_notifier_test_young(struct mm_struct *mm,
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unsigned long address)
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{
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if (mm_has_notifiers(mm))
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return __mmu_notifier_test_young(mm, address);
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return 0;
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}
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static inline void mmu_notifier_change_pte(struct mm_struct *mm,
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unsigned long address, pte_t pte)
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{
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if (mm_has_notifiers(mm))
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__mmu_notifier_change_pte(mm, address, pte);
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}
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static inline void mmu_notifier_invalidate_page(struct mm_struct *mm,
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unsigned long address)
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{
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if (mm_has_notifiers(mm))
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__mmu_notifier_invalidate_page(mm, address);
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}
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static inline void mmu_notifier_invalidate_range_start(struct mm_struct *mm,
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unsigned long start, unsigned long end)
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{
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if (mm_has_notifiers(mm))
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__mmu_notifier_invalidate_range_start(mm, start, end);
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}
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static inline void mmu_notifier_invalidate_range_end(struct mm_struct *mm,
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unsigned long start, unsigned long end)
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{
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if (mm_has_notifiers(mm))
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__mmu_notifier_invalidate_range_end(mm, start, end);
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}
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static inline void mmu_notifier_mm_init(struct mm_struct *mm)
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{
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mm->mmu_notifier_mm = NULL;
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}
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static inline void mmu_notifier_mm_destroy(struct mm_struct *mm)
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{
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if (mm_has_notifiers(mm))
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__mmu_notifier_mm_destroy(mm);
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}
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/*
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* These two macros will sometime replace ptep_clear_flush.
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* ptep_clear_flush is implemented as macro itself, so this also is
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* implemented as a macro until ptep_clear_flush will converted to an
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* inline function, to diminish the risk of compilation failure. The
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* invalidate_page method over time can be moved outside the PT lock
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* and these two macros can be later removed.
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*/
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#define ptep_clear_flush_notify(__vma, __address, __ptep) \
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({ \
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pte_t __pte; \
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struct vm_area_struct *___vma = __vma; \
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unsigned long ___address = __address; \
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__pte = ptep_clear_flush(___vma, ___address, __ptep); \
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mmu_notifier_invalidate_page(___vma->vm_mm, ___address); \
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__pte; \
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})
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#define pmdp_clear_flush_notify(__vma, __address, __pmdp) \
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({ \
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pmd_t __pmd; \
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struct vm_area_struct *___vma = __vma; \
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unsigned long ___address = __address; \
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VM_BUG_ON(__address & ~HPAGE_PMD_MASK); \
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mmu_notifier_invalidate_range_start(___vma->vm_mm, ___address, \
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(__address)+HPAGE_PMD_SIZE);\
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__pmd = pmdp_clear_flush(___vma, ___address, __pmdp); \
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mmu_notifier_invalidate_range_end(___vma->vm_mm, ___address, \
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(__address)+HPAGE_PMD_SIZE); \
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__pmd; \
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})
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#define pmdp_splitting_flush_notify(__vma, __address, __pmdp) \
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({ \
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struct vm_area_struct *___vma = __vma; \
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unsigned long ___address = __address; \
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VM_BUG_ON(__address & ~HPAGE_PMD_MASK); \
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mmu_notifier_invalidate_range_start(___vma->vm_mm, ___address, \
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(__address)+HPAGE_PMD_SIZE);\
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pmdp_splitting_flush(___vma, ___address, __pmdp); \
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mmu_notifier_invalidate_range_end(___vma->vm_mm, ___address, \
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(__address)+HPAGE_PMD_SIZE); \
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})
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#define ptep_clear_flush_young_notify(__vma, __address, __ptep) \
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({ \
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int __young; \
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struct vm_area_struct *___vma = __vma; \
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unsigned long ___address = __address; \
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__young = ptep_clear_flush_young(___vma, ___address, __ptep); \
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__young |= mmu_notifier_clear_flush_young(___vma->vm_mm, \
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___address); \
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__young; \
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})
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#define pmdp_clear_flush_young_notify(__vma, __address, __pmdp) \
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({ \
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int __young; \
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struct vm_area_struct *___vma = __vma; \
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unsigned long ___address = __address; \
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__young = pmdp_clear_flush_young(___vma, ___address, __pmdp); \
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__young |= mmu_notifier_clear_flush_young(___vma->vm_mm, \
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___address); \
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__young; \
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})
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#define set_pte_at_notify(__mm, __address, __ptep, __pte) \
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({ \
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struct mm_struct *___mm = __mm; \
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unsigned long ___address = __address; \
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pte_t ___pte = __pte; \
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\
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set_pte_at(___mm, ___address, __ptep, ___pte); \
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mmu_notifier_change_pte(___mm, ___address, ___pte); \
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})
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#else /* CONFIG_MMU_NOTIFIER */
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static inline void mmu_notifier_release(struct mm_struct *mm)
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{
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}
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static inline int mmu_notifier_clear_flush_young(struct mm_struct *mm,
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unsigned long address)
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{
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return 0;
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}
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static inline int mmu_notifier_test_young(struct mm_struct *mm,
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unsigned long address)
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{
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return 0;
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}
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static inline void mmu_notifier_change_pte(struct mm_struct *mm,
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unsigned long address, pte_t pte)
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{
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}
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static inline void mmu_notifier_invalidate_page(struct mm_struct *mm,
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unsigned long address)
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{
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}
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static inline void mmu_notifier_invalidate_range_start(struct mm_struct *mm,
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unsigned long start, unsigned long end)
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{
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}
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static inline void mmu_notifier_invalidate_range_end(struct mm_struct *mm,
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unsigned long start, unsigned long end)
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{
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}
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static inline void mmu_notifier_mm_init(struct mm_struct *mm)
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{
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}
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static inline void mmu_notifier_mm_destroy(struct mm_struct *mm)
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{
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}
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#define ptep_clear_flush_young_notify ptep_clear_flush_young
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#define pmdp_clear_flush_young_notify pmdp_clear_flush_young
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#define ptep_clear_flush_notify ptep_clear_flush
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#define pmdp_clear_flush_notify pmdp_clear_flush
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#define pmdp_splitting_flush_notify pmdp_splitting_flush
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#define set_pte_at_notify set_pte_at
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#endif /* CONFIG_MMU_NOTIFIER */
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#endif /* _LINUX_MMU_NOTIFIER_H */
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