mmu-notifier: add clear_young callback

[deliverable/linux.git] / virt / kvm / kvm_main.c

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index d8db2f8fce9c7ab727fb5dfa957d5f7ba828fa42..268fc0a5a9324f597214d41572952b52aeb76299 100644 (file)
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -387,6 +387,36 @@ static int kvm_mmu_notifier_clear_flush_young(struct mmu_notifier *mn,
        return young;
 }
 
+static int kvm_mmu_notifier_clear_young(struct mmu_notifier *mn,
+                                       struct mm_struct *mm,
+                                       unsigned long start,
+                                       unsigned long end)
+{
+       struct kvm *kvm = mmu_notifier_to_kvm(mn);
+       int young, idx;
+
+       idx = srcu_read_lock(&kvm->srcu);
+       spin_lock(&kvm->mmu_lock);
+       /*
+        * Even though we do not flush TLB, this will still adversely
+        * affect performance on pre-Haswell Intel EPT, where there is
+        * no EPT Access Bit to clear so that we have to tear down EPT
+        * tables instead. If we find this unacceptable, we can always
+        * add a parameter to kvm_age_hva so that it effectively doesn't
+        * do anything on clear_young.
+        *
+        * Also note that currently we never issue secondary TLB flushes
+        * from clear_young, leaving this job up to the regular system
+        * cadence. If we find this inaccurate, we might come up with a
+        * more sophisticated heuristic later.
+        */
+       young = kvm_age_hva(kvm, start, end);
+       spin_unlock(&kvm->mmu_lock);
+       srcu_read_unlock(&kvm->srcu, idx);
+
+       return young;
+}
+
 static int kvm_mmu_notifier_test_young(struct mmu_notifier *mn,
                                       struct mm_struct *mm,
                                       unsigned long address)
@@ -419,6 +449,7 @@ static const struct mmu_notifier_ops kvm_mmu_notifier_ops = {
        .invalidate_range_start = kvm_mmu_notifier_invalidate_range_start,
        .invalidate_range_end   = kvm_mmu_notifier_invalidate_range_end,
        .clear_flush_young      = kvm_mmu_notifier_clear_flush_young,
+       .clear_young            = kvm_mmu_notifier_clear_young,
        .test_young             = kvm_mmu_notifier_test_young,
        .change_pte             = kvm_mmu_notifier_change_pte,
        .release                = kvm_mmu_notifier_release,