[2/2] KVM: x86: pre-allocate one more dirty bitmap to avoid vmalloc() in kvm_vm_ioctl_get_dirty_log()

Commit Message

Takuya Yoshikawa June 3, 2010, 1:06 p.m. UTC

None

Patch

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 0cd0f29..c516f1c 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -81,6 +81,8 @@ 
 #define KVM_NR_FIXED_MTRR_REGION 88
 #define KVM_NR_VAR_MTRR 8
 
+#define __KVM_DIRTY_LOG_DOUBLE_BUFFERING
+
 extern spinlock_t kvm_lock;
 extern struct list_head vm_list;
 
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 5e5cd8d..0871ef8 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2804,18 +2804,15 @@  int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm,
 		kvm_mmu_slot_remove_write_access(kvm, log->slot);
 		spin_unlock(&kvm->mmu_lock);
 
-		r = -ENOMEM;
-		dirty_bitmap = vmalloc(n);
-		if (!dirty_bitmap)
-			goto out;
+		dirty_bitmap = memslot->dirty_bitmap_head;
+		if (memslot->dirty_bitmap == dirty_bitmap)
+			dirty_bitmap += n / sizeof(long);
 		memset(dirty_bitmap, 0, n);
 
 		r = -ENOMEM;
 		slots = kzalloc(sizeof(struct kvm_memslots), GFP_KERNEL);
-		if (!slots) {
-			vfree(dirty_bitmap);
+		if (!slots)
 			goto out;
-		}
 		memcpy(slots, kvm->memslots, sizeof(struct kvm_memslots));
 		slots->memslots[log->slot].dirty_bitmap = dirty_bitmap;
 
@@ -2826,11 +2823,8 @@  int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm,
 		kfree(old_slots);
 
 		r = -EFAULT;
-		if (copy_to_user(log->dirty_bitmap, dirty_bitmap, n)) {
-			vfree(dirty_bitmap);
+		if (copy_to_user(log->dirty_bitmap, dirty_bitmap, n))
 			goto out;
-		}
-		vfree(dirty_bitmap);
 	} else {
 		r = -EFAULT;
 		if (clear_user(log->dirty_bitmap, n))
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 2c62319..199a464 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -118,6 +118,9 @@  struct kvm_memory_slot {
 	unsigned long flags;
 	unsigned long *rmap;
 	unsigned long *dirty_bitmap;
+#ifdef __KVM_DIRTY_LOG_DOUBLE_BUFFERING
+	unsigned long *dirty_bitmap_head;
+#endif
 	struct {
 		unsigned long rmap_pde;
 		int write_count;
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index e4f5762..6f73b42 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -443,7 +443,10 @@  static void kvm_destroy_dirty_bitmap(struct kvm_memory_slot *memslot)
 {
 	if (!memslot->dirty_bitmap)
 		return;
-
+#ifdef __KVM_DIRTY_LOG_DOUBLE_BUFFERING
+	memslot->dirty_bitmap = memslot->dirty_bitmap_head;
+	memslot->dirty_bitmap_head = NULL;
+#endif
 	vfree(memslot->dirty_bitmap);
 	memslot->dirty_bitmap = NULL;
 }
@@ -535,12 +538,17 @@  static int kvm_vm_release(struct inode *inode, struct file *filp)
 static int kvm_create_dirty_bitmap(struct kvm_memory_slot *memslot)
 {
 	unsigned long dirty_bytes = kvm_dirty_bitmap_bytes(memslot);
-
+#ifdef __KVM_DIRTY_LOG_DOUBLE_BUFFERING
+	dirty_bytes *= 2;
+#endif
 	memslot->dirty_bitmap = vmalloc(dirty_bytes);
 	if (!memslot->dirty_bitmap)
 		return -ENOMEM;
 
 	memset(memslot->dirty_bitmap, 0, dirty_bytes);
+#ifdef __KVM_DIRTY_LOG_DOUBLE_BUFFERING
+	memslot->dirty_bitmap_head = memslot->dirty_bitmap;
+#endif
 	return 0;
 }