3 files changed, 40 insertions, 15 deletions

diff --git a/drivers/kvm/kvm.h b/drivers/kvm/kvm.h
index bdcc44e6b6d7..c1aa84f7ca0a 100644
--- a/drivers/kvm/kvm.h
+++ b/drivers/kvm/kvm.h
@@ -644,6 +644,11 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu);
 
 int kvm_dev_ioctl_check_extension(long ext);
 
+int kvm_get_dirty_log(struct kvm *kvm,
+                        struct kvm_dirty_log *log, int *is_dirty);
+int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm,
+                                struct kvm_dirty_log *log);
+
 int kvm_vm_ioctl_set_memory_region(struct kvm *kvm,
                                    struct
                                    kvm_userspace_memory_region *mem,
diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c
index b0b6ff2a8cbe..5f11e6b09458 100644
--- a/drivers/kvm/kvm_main.c
+++ b/drivers/kvm/kvm_main.c
@@ -389,19 +389,14 @@ int kvm_vm_ioctl_set_memory_region(struct kvm *kvm,
         return kvm_set_memory_region(kvm, mem, user_alloc);
 }
 
-/*
- * Get (and clear) the dirty memory log for a memory slot.
- */
-static int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm,
-                                      struct kvm_dirty_log *log)
+int kvm_get_dirty_log(struct kvm *kvm,
+                        struct kvm_dirty_log *log, int *is_dirty)
 {
         struct kvm_memory_slot *memslot;
         int r, i;
         int n;
         unsigned long any = 0;
 
-        mutex_lock(&kvm->lock);
-
         r = -EINVAL;
         if (log->slot >= KVM_MEMORY_SLOTS)
                 goto out;
@@ -420,17 +415,11 @@ static int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm,
         if (copy_to_user(log->dirty_bitmap, memslot->dirty_bitmap, n))
                 goto out;
 
-        /* If nothing is dirty, don't bother messing with page tables. */
-        if (any) {
-                kvm_mmu_slot_remove_write_access(kvm, log->slot);
-                kvm_flush_remote_tlbs(kvm);
-                memset(memslot->dirty_bitmap, 0, n);
-        }
+        if (any)
+                *is_dirty = 1;
 
         r = 0;
-
 out:
-        mutex_unlock(&kvm->lock);
         return r;
 }
 
diff --git a/drivers/kvm/x86.c b/drivers/kvm/x86.c
index 9618fcba887e..935e2769b787 100644
--- a/drivers/kvm/x86.c
+++ b/drivers/kvm/x86.c
@@ -937,6 +937,37 @@ static int kvm_vm_ioctl_set_irqchip(struct kvm *kvm, struct kvm_irqchip *chip)
         return r;
 }
 
+/*
+ * Get (and clear) the dirty memory log for a memory slot.
+ */
+int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm,
+                                      struct kvm_dirty_log *log)
+{
+        int r;
+        int n;
+        struct kvm_memory_slot *memslot;
+        int is_dirty = 0;
+
+        mutex_lock(&kvm->lock);
+
+        r = kvm_get_dirty_log(kvm, log, &is_dirty);
+        if (r)
+                goto out;
+
+        /* If nothing is dirty, don't bother messing with page tables. */
+        if (is_dirty) {
+                kvm_mmu_slot_remove_write_access(kvm, log->slot);
+                kvm_flush_remote_tlbs(kvm);
+                memslot = &kvm->memslots[log->slot];
+                n = ALIGN(memslot->npages, BITS_PER_LONG) / 8;
+                memset(memslot->dirty_bitmap, 0, n);
+        }
+        r = 0;
+out:
+        mutex_unlock(&kvm->lock);
+        return r;
+}
+
 long kvm_arch_vm_ioctl(struct file *filp,
                        unsigned int ioctl, unsigned long arg)
 {