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>

16 files changed, 71 insertions, 41 deletions

diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
index 032a8538318a..8c3f7eb62b54 100644
--- a/arch/arm/include/asm/kvm_host.h
+++ b/arch/arm/include/asm/kvm_host.h
@@ -170,7 +170,8 @@ unsigned long kvm_arm_num_regs(struct kvm_vcpu *vcpu);
 int kvm_arm_copy_reg_indices(struct kvm_vcpu *vcpu, u64 __user *indices);
 
 /* We do not have shadow page tables, hence the empty hooks */
-static inline int kvm_age_hva(struct kvm *kvm, unsigned long hva)
+static inline int kvm_age_hva(struct kvm *kvm, unsigned long start,
+                              unsigned long end)
 {
         return 0;
 }
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index be9970a59497..a3c671b3acc9 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -180,7 +180,8 @@ int kvm_unmap_hva_range(struct kvm *kvm,
 void kvm_set_spte_hva(struct kvm *kvm, unsigned long hva, pte_t pte);
 
 /* We do not have shadow page tables, hence the empty hooks */
-static inline int kvm_age_hva(struct kvm *kvm, unsigned long hva)
+static inline int kvm_age_hva(struct kvm *kvm, unsigned long start,
+                              unsigned long end)
 {
         return 0;
 }
diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h
index 604000882352..d329bc5543a2 100644
--- a/arch/powerpc/include/asm/kvm_host.h
+++ b/arch/powerpc/include/asm/kvm_host.h
@@ -56,7 +56,7 @@
 extern int kvm_unmap_hva(struct kvm *kvm, unsigned long hva);
 extern int kvm_unmap_hva_range(struct kvm *kvm,
                                unsigned long start, unsigned long end);
-extern int kvm_age_hva(struct kvm *kvm, unsigned long hva);
+extern int kvm_age_hva(struct kvm *kvm, unsigned long start, unsigned long end);
 extern int kvm_test_age_hva(struct kvm *kvm, unsigned long hva);
 extern void kvm_set_spte_hva(struct kvm *kvm, unsigned long hva, pte_t pte);
 
diff --git a/arch/powerpc/include/asm/kvm_ppc.h b/arch/powerpc/include/asm/kvm_ppc.h
index fb86a2299d8a..d4a92d7cea6a 100644
--- a/arch/powerpc/include/asm/kvm_ppc.h
+++ b/arch/powerpc/include/asm/kvm_ppc.h
@@ -243,7 +243,7 @@ struct kvmppc_ops {
         int (*unmap_hva)(struct kvm *kvm, unsigned long hva);
         int (*unmap_hva_range)(struct kvm *kvm, unsigned long start,
                            unsigned long end);
-        int (*age_hva)(struct kvm *kvm, unsigned long hva);
+        int (*age_hva)(struct kvm *kvm, unsigned long start, unsigned long end);
         int (*test_age_hva)(struct kvm *kvm, unsigned long hva);
         void (*set_spte_hva)(struct kvm *kvm, unsigned long hva, pte_t pte);
         void (*mmu_destroy)(struct kvm_vcpu *vcpu);
diff --git a/arch/powerpc/kvm/book3s.c b/arch/powerpc/kvm/book3s.c
index dd03f6b299ba..c16cfbfeb781 100644
--- a/arch/powerpc/kvm/book3s.c
+++ b/arch/powerpc/kvm/book3s.c
@@ -851,9 +851,9 @@ int kvm_unmap_hva_range(struct kvm *kvm, unsigned long start, unsigned long end)
         return kvm->arch.kvm_ops->unmap_hva_range(kvm, start, end);
 }
 
-int kvm_age_hva(struct kvm *kvm, unsigned long hva)
+int kvm_age_hva(struct kvm *kvm, unsigned long start, unsigned long end)
 {
-        return kvm->arch.kvm_ops->age_hva(kvm, hva);
+        return kvm->arch.kvm_ops->age_hva(kvm, start, end);
 }
 
 int kvm_test_age_hva(struct kvm *kvm, unsigned long hva)
diff --git a/arch/powerpc/kvm/book3s.h b/arch/powerpc/kvm/book3s.h
index 4bf956cf94d6..d2b3ec088b8c 100644
--- a/arch/powerpc/kvm/book3s.h
+++ b/arch/powerpc/kvm/book3s.h
@@ -17,7 +17,8 @@ extern void kvmppc_core_flush_memslot_hv(struct kvm *kvm,
 extern int kvm_unmap_hva_hv(struct kvm *kvm, unsigned long hva);
 extern int kvm_unmap_hva_range_hv(struct kvm *kvm, unsigned long start,
                                   unsigned long end);
-extern int kvm_age_hva_hv(struct kvm *kvm, unsigned long hva);
+extern int kvm_age_hva_hv(struct kvm *kvm, unsigned long start,
+                          unsigned long end);
 extern int kvm_test_age_hva_hv(struct kvm *kvm, unsigned long hva);
 extern void kvm_set_spte_hva_hv(struct kvm *kvm, unsigned long hva, pte_t pte);
 
diff --git a/arch/powerpc/kvm/book3s_64_mmu_hv.c b/arch/powerpc/kvm/book3s_64_mmu_hv.c
index 72c20bb16d26..81460c5359c0 100644
--- a/arch/powerpc/kvm/book3s_64_mmu_hv.c
+++ b/arch/powerpc/kvm/book3s_64_mmu_hv.c
@@ -1002,11 +1002,11 @@ static int kvm_age_rmapp(struct kvm *kvm, unsigned long *rmapp,
         return ret;
 }
 
-int kvm_age_hva_hv(struct kvm *kvm, unsigned long hva)
+int kvm_age_hva_hv(struct kvm *kvm, unsigned long start, unsigned long end)
 {
         if (!kvm->arch.using_mmu_notifiers)
                 return 0;
-        return kvm_handle_hva(kvm, hva, kvm_age_rmapp);
+        return kvm_handle_hva_range(kvm, start, end, kvm_age_rmapp);
 }
 
 static int kvm_test_age_rmapp(struct kvm *kvm, unsigned long *rmapp,
diff --git a/arch/powerpc/kvm/book3s_pr.c b/arch/powerpc/kvm/book3s_pr.c
index faffb27badd9..852fcd8951c4 100644
--- a/arch/powerpc/kvm/book3s_pr.c
+++ b/arch/powerpc/kvm/book3s_pr.c
@@ -295,7 +295,8 @@ static int kvm_unmap_hva_range_pr(struct kvm *kvm, unsigned long start,
         return 0;
 }
 
-static int kvm_age_hva_pr(struct kvm *kvm, unsigned long hva)
+static int kvm_age_hva_pr(struct kvm *kvm, unsigned long start,
+                          unsigned long end)
 {
         /* XXX could be more clever ;) */
         return 0;
diff --git a/arch/powerpc/kvm/e500_mmu_host.c b/arch/powerpc/kvm/e500_mmu_host.c
index 08f14bb57897..b1f3f630315e 100644
--- a/arch/powerpc/kvm/e500_mmu_host.c
+++ b/arch/powerpc/kvm/e500_mmu_host.c
@@ -732,7 +732,7 @@ int kvm_unmap_hva_range(struct kvm *kvm, unsigned long start, unsigned long end)
         return 0;
 }
 
-int kvm_age_hva(struct kvm *kvm, unsigned long hva)
+int kvm_age_hva(struct kvm *kvm, unsigned long start, unsigned long end)
 {
         /* XXX could be more clever ;) */
         return 0;
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index eeeb573fcf6f..763d273cab1d 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1035,7 +1035,7 @@ asmlinkage void kvm_spurious_fault(void);
 #define KVM_ARCH_WANT_MMU_NOTIFIER
 int kvm_unmap_hva(struct kvm *kvm, unsigned long hva);
 int kvm_unmap_hva_range(struct kvm *kvm, unsigned long start, unsigned long end);
-int kvm_age_hva(struct kvm *kvm, unsigned long hva);
+int kvm_age_hva(struct kvm *kvm, unsigned long start, unsigned long end);
 int kvm_test_age_hva(struct kvm *kvm, unsigned long hva);
 void kvm_set_spte_hva(struct kvm *kvm, unsigned long hva, pte_t pte);
 int cpuid_maxphyaddr(struct kvm_vcpu *vcpu);
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 47d534066325..3201e93ebd07 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -1417,18 +1417,7 @@ static int kvm_age_rmapp(struct kvm *kvm, unsigned long *rmapp,
         struct rmap_iterator uninitialized_var(iter);
         int young = 0;
 
-        /*
-         * In case of absence of EPT Access and Dirty Bits supports,
-         * emulate the accessed bit for EPT, by checking if this page has
-         * an EPT mapping, and clearing it if it does. On the next access,
-         * a new EPT mapping will be established.
-         * This has some overhead, but not as much as the cost of swapping
-         * out actively used pages or breaking up actively used hugepages.
-         */
-        if (!shadow_accessed_mask) {
-                young = kvm_unmap_rmapp(kvm, rmapp, slot, gfn, level, data);
-                goto out;
-        }
+        BUG_ON(!shadow_accessed_mask);
 
         for (sptep = rmap_get_first(*rmapp, &iter); sptep;
              sptep = rmap_get_next(&iter)) {
@@ -1440,7 +1429,6 @@ static int kvm_age_rmapp(struct kvm *kvm, unsigned long *rmapp,
                                  (unsigned long *)sptep);
                 }
         }
-out:
         trace_kvm_age_page(gfn, level, slot, young);
         return young;
 }
@@ -1489,9 +1477,29 @@ static void rmap_recycle(struct kvm_vcpu *vcpu, u64 *spte, gfn_t gfn)
         kvm_flush_remote_tlbs(vcpu->kvm);
 }
 
-int kvm_age_hva(struct kvm *kvm, unsigned long hva)
+int kvm_age_hva(struct kvm *kvm, unsigned long start, unsigned long end)
 {
-        return kvm_handle_hva(kvm, hva, 0, kvm_age_rmapp);
+        /*
+         * In case of absence of EPT Access and Dirty Bits supports,
+         * emulate the accessed bit for EPT, by checking if this page has
+         * an EPT mapping, and clearing it if it does. On the next access,
+         * a new EPT mapping will be established.
+         * This has some overhead, but not as much as the cost of swapping
+         * out actively used pages or breaking up actively used hugepages.
+         */
+        if (!shadow_accessed_mask) {
+                /*
+                 * We are holding the kvm->mmu_lock, and we are blowing up
+                 * shadow PTEs. MMU notifier consumers need to be kept at bay.
+                 * This is correct as long as we don't decouple the mmu_lock
+                 * protected regions (like invalidate_range_start|end does).
+                 */
+                kvm->mmu_notifier_seq++;
+                return kvm_handle_hva_range(kvm, start, end, 0,
+                                            kvm_unmap_rmapp);
+        }
+
+        return kvm_handle_hva_range(kvm, start, end, 0, kvm_age_rmapp);
 }
 
 int kvm_test_age_hva(struct kvm *kvm, unsigned long hva)
diff --git a/drivers/iommu/amd_iommu_v2.c b/drivers/iommu/amd_iommu_v2.c
index 5f578e850fc5..90d734bbf467 100644
--- a/drivers/iommu/amd_iommu_v2.c
+++ b/drivers/iommu/amd_iommu_v2.c
@@ -402,9 +402,11 @@ static void __mn_flush_page(struct mmu_notifier *mn,
 
 static int mn_clear_flush_young(struct mmu_notifier *mn,
                                 struct mm_struct *mm,
-                                unsigned long address)
+                                unsigned long start,
+                                unsigned long end)
 {
-        __mn_flush_page(mn, address);
+        for (; start < end; start += PAGE_SIZE)
+                __mn_flush_page(mn, start);
 
         return 0;
 }
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;
 }
diff --git a/mm/mmu_notifier.c b/mm/mmu_notifier.c
index 950813b1eb36..2c8da9825fe3 100644
--- a/mm/mmu_notifier.c
+++ b/mm/mmu_notifier.c
@@ -107,7 +107,8 @@ void __mmu_notifier_release(struct mm_struct *mm)
  * existed or not.
  */
 int __mmu_notifier_clear_flush_young(struct mm_struct *mm,
-                                        unsigned long address)
+                                        unsigned long start,
+                                        unsigned long end)
 {
         struct mmu_notifier *mn;
         int young = 0, id;
@@ -115,7 +116,7 @@ int __mmu_notifier_clear_flush_young(struct mm_struct *mm,
         id = srcu_read_lock(&srcu);
         hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) {
                 if (mn->ops->clear_flush_young)
-                        young |= mn->ops->clear_flush_young(mn, mm, address);
+                        young |= mn->ops->clear_flush_young(mn, mm, start, end);
         }
         srcu_read_unlock(&srcu, id);
 
diff --git a/mm/rmap.c b/mm/rmap.c
index 3e8491c504f8..bc74e0012809 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1355,7 +1355,11 @@ static int try_to_unmap_cluster(unsigned long cursor, unsigned int *mapcount,
                         continue;       /* don't unmap */
                 }
 
-                if (ptep_clear_flush_young_notify(vma, address, pte))
+                /*
+                 * No need for _notify because we're within an
+                 * mmu_notifier_invalidate_range_ {start|end} scope.
+                 */
+                if (ptep_clear_flush_young(vma, address, pte))
                         continue;
 
                 /* Nuke the page table entry. */
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index ff42b11d2b9c..0316314d48f4 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -369,7 +369,8 @@ static void kvm_mmu_notifier_invalidate_range_end(struct mmu_notifier *mn,
 
 static int kvm_mmu_notifier_clear_flush_young(struct mmu_notifier *mn,
                                               struct mm_struct *mm,
-                                              unsigned long address)
+                                              unsigned long start,
+                                              unsigned long end)
 {
         struct kvm *kvm = mmu_notifier_to_kvm(mn);
         int young, idx;
@@ -377,7 +378,7 @@ static int kvm_mmu_notifier_clear_flush_young(struct mmu_notifier *mn,
         idx = srcu_read_lock(&kvm->srcu);
         spin_lock(&kvm->mmu_lock);
 
-        young = kvm_age_hva(kvm, address);
+        young = kvm_age_hva(kvm, start, end);
         if (young)
                 kvm_flush_remote_tlbs(kvm);