KVM: Synchronize guest physical memory map to host virtual memory map

[net-next-2.6.git] / virt / kvm / kvm_main.c

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 3735212cd3f807b7c7cb8b7b9135069f1cfe5935..7dd9b0b85e4eea1aafaff116e993e6392c9cc173 100644 (file)
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -192,6 +192,123 @@ void kvm_vcpu_uninit(struct kvm_vcpu *vcpu)
 }
 EXPORT_SYMBOL_GPL(kvm_vcpu_uninit);
 
+#if defined(CONFIG_MMU_NOTIFIER) && defined(KVM_ARCH_WANT_MMU_NOTIFIER)
+static inline struct kvm *mmu_notifier_to_kvm(struct mmu_notifier *mn)
+{
+       return container_of(mn, struct kvm, mmu_notifier);
+}
+
+static void kvm_mmu_notifier_invalidate_page(struct mmu_notifier *mn,
+                                            struct mm_struct *mm,
+                                            unsigned long address)
+{
+       struct kvm *kvm = mmu_notifier_to_kvm(mn);
+       int need_tlb_flush;
+
+       /*
+        * When ->invalidate_page runs, the linux pte has been zapped
+        * already but the page is still allocated until
+        * ->invalidate_page returns. So if we increase the sequence
+        * here the kvm page fault will notice if the spte can't be
+        * established because the page is going to be freed. If
+        * instead the kvm page fault establishes the spte before
+        * ->invalidate_page runs, kvm_unmap_hva will release it
+        * before returning.
+        *
+        * The sequence increase only need to be seen at spin_unlock
+        * time, and not at spin_lock time.
+        *
+        * Increasing the sequence after the spin_unlock would be
+        * unsafe because the kvm page fault could then establish the
+        * pte after kvm_unmap_hva returned, without noticing the page
+        * is going to be freed.
+        */
+       spin_lock(&kvm->mmu_lock);
+       kvm->mmu_notifier_seq++;
+       need_tlb_flush = kvm_unmap_hva(kvm, address);
+       spin_unlock(&kvm->mmu_lock);
+
+       /* we've to flush the tlb before the pages can be freed */
+       if (need_tlb_flush)
+               kvm_flush_remote_tlbs(kvm);
+
+}
+
+static void kvm_mmu_notifier_invalidate_range_start(struct mmu_notifier *mn,
+                                                   struct mm_struct *mm,
+                                                   unsigned long start,
+                                                   unsigned long end)
+{
+       struct kvm *kvm = mmu_notifier_to_kvm(mn);
+       int need_tlb_flush = 0;
+
+       spin_lock(&kvm->mmu_lock);
+       /*
+        * The count increase must become visible at unlock time as no
+        * spte can be established without taking the mmu_lock and
+        * count is also read inside the mmu_lock critical section.
+        */
+       kvm->mmu_notifier_count++;
+       for (; start < end; start += PAGE_SIZE)
+               need_tlb_flush |= kvm_unmap_hva(kvm, start);
+       spin_unlock(&kvm->mmu_lock);
+
+       /* we've to flush the tlb before the pages can be freed */
+       if (need_tlb_flush)
+               kvm_flush_remote_tlbs(kvm);
+}
+
+static void kvm_mmu_notifier_invalidate_range_end(struct mmu_notifier *mn,
+                                                 struct mm_struct *mm,
+                                                 unsigned long start,
+                                                 unsigned long end)
+{
+       struct kvm *kvm = mmu_notifier_to_kvm(mn);
+
+       spin_lock(&kvm->mmu_lock);
+       /*
+        * This sequence increase will notify the kvm page fault that
+        * the page that is going to be mapped in the spte could have
+        * been freed.
+        */
+       kvm->mmu_notifier_seq++;
+       /*
+        * The above sequence increase must be visible before the
+        * below count decrease but both values are read by the kvm
+        * page fault under mmu_lock spinlock so we don't need to add
+        * a smb_wmb() here in between the two.
+        */
+       kvm->mmu_notifier_count--;
+       spin_unlock(&kvm->mmu_lock);
+
+       BUG_ON(kvm->mmu_notifier_count < 0);
+}
+
+static int kvm_mmu_notifier_clear_flush_young(struct mmu_notifier *mn,
+                                             struct mm_struct *mm,
+                                             unsigned long address)
+{
+       struct kvm *kvm = mmu_notifier_to_kvm(mn);
+       int young;
+
+       spin_lock(&kvm->mmu_lock);
+       young = kvm_age_hva(kvm, address);
+       spin_unlock(&kvm->mmu_lock);
+
+       if (young)
+               kvm_flush_remote_tlbs(kvm);
+
+       return young;
+}
+
+static const struct mmu_notifier_ops kvm_mmu_notifier_ops = {
+       .invalidate_page        = kvm_mmu_notifier_invalidate_page,
+       .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,
+};
+#endif /* CONFIG_MMU_NOTIFIER && KVM_ARCH_WANT_MMU_NOTIFIER */
+
 static struct kvm *kvm_create_vm(void)
 {
        struct kvm *kvm = kvm_arch_create_vm();
@@ -212,6 +329,21 @@ static struct kvm *kvm_create_vm(void)
                        (struct kvm_coalesced_mmio_ring *)page_address(page);
 #endif
 
+#if defined(CONFIG_MMU_NOTIFIER) && defined(KVM_ARCH_WANT_MMU_NOTIFIER)
+       {
+               int err;
+               kvm->mmu_notifier.ops = &kvm_mmu_notifier_ops;
+               err = mmu_notifier_register(&kvm->mmu_notifier, current->mm);
+               if (err) {
+#ifdef KVM_COALESCED_MMIO_PAGE_OFFSET
+                       put_page(page);
+#endif
+                       kfree(kvm);
+                       return ERR_PTR(err);
+               }
+       }
+#endif
+
        kvm->mm = current->mm;
        atomic_inc(&kvm->mm->mm_count);
        spin_lock_init(&kvm->mmu_lock);
@@ -271,6 +403,9 @@ static void kvm_destroy_vm(struct kvm *kvm)
 #ifdef KVM_COALESCED_MMIO_PAGE_OFFSET
        if (kvm->coalesced_mmio_ring != NULL)
                free_page((unsigned long)kvm->coalesced_mmio_ring);
+#endif
+#if defined(CONFIG_MMU_NOTIFIER) && defined(KVM_ARCH_WANT_MMU_NOTIFIER)
+       mmu_notifier_unregister(&kvm->mmu_notifier, kvm->mm);
 #endif
        kvm_arch_destroy_vm(kvm);
        mmdrop(mm);