static int kvm_vm_ioctl_enable_dirty_log_ring(struct kvm *kvm, u32 size)
{
	int r;

	if (!KVM_DIRTY_LOG_PAGE_OFFSET)
		return -EINVAL;

	/* the size should be power of 2 */
	if (!size || (size & (size - 1)))
		return -EINVAL;

	/* Should be bigger to keep the reserved entries, or a page */
	if (size < kvm_dirty_ring_get_rsvd_entries() *
	    sizeof(struct kvm_dirty_gfn) || size < PAGE_SIZE)
		return -EINVAL;

	if (size > KVM_DIRTY_RING_MAX_ENTRIES *
	    sizeof(struct kvm_dirty_gfn))
		return -E2BIG;

	/* We only allow it to set once */
	if (kvm->dirty_ring_size)
		return -EINVAL;

	mutex_lock(&kvm->lock);

	if (kvm->created_vcpus) {
		/* We don't allow to change this value after vcpu created */
		r = -EINVAL;
	} else {
		kvm->dirty_ring_size = size;
		r = 0;
	}

	mutex_unlock(&kvm->lock);
	return r;
}