[RFC,v2,1/6] KVM: introduce slot level dirty state management

Commit Message

Takuya Yoshikawa April 20, 2010, 10:56 a.m. UTC

None

Patch

diff --git a/arch/ia64/kvm/kvm-ia64.c b/arch/ia64/kvm/kvm-ia64.c
index d7bac1f..d60dafe 100644
--- a/arch/ia64/kvm/kvm-ia64.c
+++ b/arch/ia64/kvm/kvm-ia64.c
@@ -1824,6 +1824,9 @@  static int kvm_ia64_sync_dirty_log(struct kvm *kvm,
 	base = memslot->base_gfn / BITS_PER_LONG;
 
 	for (i = 0; i < n/sizeof(long); ++i) {
+		if (dirty_bitmap[base + i])
+			memslot->is_dirty = true;
+
 		memslot->dirty_bitmap[i] = dirty_bitmap[base + i];
 		dirty_bitmap[base + i] = 0;
 	}
@@ -1838,7 +1841,6 @@  int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm,
 	int r;
 	unsigned long n;
 	struct kvm_memory_slot *memslot;
-	int is_dirty = 0;
 
 	mutex_lock(&kvm->slots_lock);
 	spin_lock(&kvm->arch.dirty_log_lock);
@@ -1847,16 +1849,17 @@  int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm,
 	if (r)
 		goto out;
 
-	r = kvm_get_dirty_log(kvm, log, &is_dirty);
+	r = kvm_get_dirty_log(kvm, log);
 	if (r)
 		goto out;
 
+	memslot = &kvm->memslots->memslots[log->slot];
 	/* If nothing is dirty, don't bother messing with page tables. */
-	if (is_dirty) {
+	if (memslot->is_dirty) {
 		kvm_flush_remote_tlbs(kvm);
-		memslot = &kvm->memslots->memslots[log->slot];
 		n = kvm_dirty_bitmap_bytes(memslot);
 		memset(memslot->dirty_bitmap, 0, n);
+		memslot->is_dirty = false;
 	}
 	r = 0;
 out:
diff --git a/arch/powerpc/kvm/book3s.c b/arch/powerpc/kvm/book3s.c
index 41c23b6..53b45cf 100644
--- a/arch/powerpc/kvm/book3s.c
+++ b/arch/powerpc/kvm/book3s.c
@@ -1118,20 +1118,18 @@  int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm,
 	struct kvm_memory_slot *memslot;
 	struct kvm_vcpu *vcpu;
 	ulong ga, ga_end;
-	int is_dirty = 0;
 	int r;
 	unsigned long n;
 
 	mutex_lock(&kvm->slots_lock);
 
-	r = kvm_get_dirty_log(kvm, log, &is_dirty);
+	r = kvm_get_dirty_log(kvm, log);
 	if (r)
 		goto out;
 
+	memslot = &kvm->memslots->memslots[log->slot];
 	/* If nothing is dirty, don't bother messing with page tables. */
-	if (is_dirty) {
-		memslot = &kvm->memslots->memslots[log->slot];
-
+	if (memslot->is_dirty) {
 		ga = memslot->base_gfn << PAGE_SHIFT;
 		ga_end = ga + (memslot->npages << PAGE_SHIFT);
 
@@ -1140,6 +1138,7 @@  int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm,
 
 		n = kvm_dirty_bitmap_bytes(memslot);
 		memset(memslot->dirty_bitmap, 0, n);
+		memslot->is_dirty = false;
 	}
 
 	r = 0;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 58a96e6..76b23ed 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2724,10 +2724,9 @@  static int kvm_vm_ioctl_reinject(struct kvm *kvm,
 int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm,
 				      struct kvm_dirty_log *log)
 {
-	int r, i;
+	int r;
 	struct kvm_memory_slot *memslot;
 	unsigned long n;
-	unsigned long is_dirty = 0;
 	unsigned long *dirty_bitmap = NULL;
 
 	mutex_lock(&kvm->slots_lock);
@@ -2749,11 +2748,8 @@  int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm,
 		goto out;
 	memset(dirty_bitmap, 0, n);
 
-	for (i = 0; !is_dirty && i < n/sizeof(long); i++)
-		is_dirty = memslot->dirty_bitmap[i];
-
 	/* If nothing is dirty, don't bother messing with page tables. */
-	if (is_dirty) {
+	if (memslot->is_dirty) {
 		struct kvm_memslots *slots, *old_slots;
 
 		spin_lock(&kvm->mmu_lock);
@@ -2766,6 +2762,7 @@  int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm,
 
 		memcpy(slots, kvm->memslots, sizeof(struct kvm_memslots));
 		slots->memslots[log->slot].dirty_bitmap = dirty_bitmap;
+		slots->memslots[log->slot].is_dirty = false;
 
 		old_slots = kvm->memslots;
 		rcu_assign_pointer(kvm->memslots, slots);
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 5583063..4446622 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -117,6 +117,7 @@  struct kvm_memory_slot {
 	unsigned long flags;
 	unsigned long *rmap;
 	unsigned long *dirty_bitmap;
+	bool is_dirty;
 	struct {
 		unsigned long rmap_pde;
 		int write_count;
@@ -329,8 +330,7 @@  long kvm_arch_vcpu_ioctl(struct file *filp,
 
 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_get_dirty_log(struct kvm *kvm, struct kvm_dirty_log *log);
 int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm,
 				struct kvm_dirty_log *log);
 
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 3725605..cc78e07 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -764,13 +764,11 @@  int kvm_vm_ioctl_set_memory_region(struct kvm *kvm,
 	return kvm_set_memory_region(kvm, mem, user_alloc);
 }
 
-int kvm_get_dirty_log(struct kvm *kvm,
-			struct kvm_dirty_log *log, int *is_dirty)
+int kvm_get_dirty_log(struct kvm *kvm, struct kvm_dirty_log *log)
 {
 	struct kvm_memory_slot *memslot;
-	int r, i;
+	int r;
 	unsigned long n;
-	unsigned long any = 0;
 
 	r = -EINVAL;
 	if (log->slot >= KVM_MEMORY_SLOTS)
@@ -783,16 +781,10 @@  int kvm_get_dirty_log(struct kvm *kvm,
 
 	n = kvm_dirty_bitmap_bytes(memslot);
 
-	for (i = 0; !any && i < n/sizeof(long); ++i)
-		any = memslot->dirty_bitmap[i];
-
 	r = -EFAULT;
 	if (copy_to_user(log->dirty_bitmap, memslot->dirty_bitmap, n))
 		goto out;
 
-	if (any)
-		*is_dirty = 1;
-
 	r = 0;
 out:
 	return r;
@@ -1189,8 +1181,10 @@  void mark_page_dirty(struct kvm *kvm, gfn_t gfn)
 		unsigned long rel_gfn = gfn - memslot->base_gfn;
 
 		/* avoid RMW */
-		if (!generic_test_le_bit(rel_gfn, memslot->dirty_bitmap))
+		if (!generic_test_le_bit(rel_gfn, memslot->dirty_bitmap)) {
 			generic___set_le_bit(rel_gfn, memslot->dirty_bitmap);
+			memslot->is_dirty = true;
+		}
 	}
 }