kvm: Fix page ageing bugs

1. We were calling clear_flush_young_notify in unmap_one, but we are
within an mmu notifier invalidate range scope. The spte exists no more
(due to range_start) and the accessed bit info has already been
propagated (due to kvm_pfn_set_accessed). Simply call
clear_flush_young.

2. We clear_flush_young on a primary MMU PMD, but this may be mapped
as a collection of PTEs by the secondary MMU (e.g. during log-dirty).
This required expanding the interface of the clear_flush_young mmu
notifier, so a lot of code has been trivially touched.

3. In the absence of shadow_accessed_mask (e.g. EPT A bit), we emulate
the access bit by blowing the spte. This requires proper synchronizing
with MMU notifier consumers, like every other removal of spte's does.

Signed-off-by: Andres Lagar-Cavilla <andreslc@google.com>
Acked-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 17 insertions, 7 deletions

diff --git a/include/linux/mmu_notifier.h b/include/linux/mmu_notifier.h
index 27288692241e..88787bb4b3b9 100644
--- a/include/linux/mmu_notifier.h
+++ b/include/linux/mmu_notifier.h
@@ -57,10 +57,13 @@ struct mmu_notifier_ops {
          * 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 *mn,
                                  struct mm_struct *mm,
-                                 unsigned long address);
+                                 unsigned long start,
+                                 unsigned long end);
 
         /*
          * test_young is called to check the young/accessed bitflag in
@@ -175,7 +178,8 @@ extern void mmu_notifier_unregister_no_release(struct mmu_notifier *mn,
 extern void __mmu_notifier_mm_destroy(struct mm_struct *mm);
 extern void __mmu_notifier_release(struct mm_struct *mm);
 extern int __mmu_notifier_clear_flush_young(struct mm_struct *mm,
-                                          unsigned long address);
+                                          unsigned long start,
+                                          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,
@@ -194,10 +198,11 @@ static inline void mmu_notifier_release(struct mm_struct *mm)
 }
 
 static inline int mmu_notifier_clear_flush_young(struct mm_struct *mm,
-                                          unsigned long address)
+                                          unsigned long start,
+                                          unsigned long end)
 {
         if (mm_has_notifiers(mm))
-                return __mmu_notifier_clear_flush_young(mm, address);
+                return __mmu_notifier_clear_flush_young(mm, start, end);
         return 0;
 }
 
@@ -255,7 +260,9 @@ static inline void mmu_notifier_mm_destroy(struct mm_struct *mm)
         unsigned long ___address = __address;                           \
         __young = ptep_clear_flush_young(___vma, ___address, __ptep);   \
         __young |= mmu_notifier_clear_flush_young(___vma->vm_mm,        \
-                                                  ___address);          \
+                                                  ___address,           \
+                                                  ___address +          \
+                                                        PAGE_SIZE);     \
         __young;                                                        \
 })
 
@@ -266,7 +273,9 @@ static inline void mmu_notifier_mm_destroy(struct mm_struct *mm)
         unsigned long ___address = __address;                           \
         __young = pmdp_clear_flush_young(___vma, ___address, __pmdp);   \
         __young |= mmu_notifier_clear_flush_young(___vma->vm_mm,        \
-                                                  ___address);          \
+                                                  ___address,           \
+                                                  ___address +          \
+                                                        PMD_SIZE);      \
         __young;                                                        \
 })
 
@@ -301,7 +310,8 @@ static inline void mmu_notifier_release(struct mm_struct *mm)
 }
 
 static inline int mmu_notifier_clear_flush_young(struct mm_struct *mm,
-                                          unsigned long address)
+                                          unsigned long start,
+                                          unsigned long end)
 {
         return 0;
 }