KVM: Add API to retrieve the number of supported vcpus per vm

Signed-off-by: Avi Kivity <avi@qumranet.com>
diff --git a/include/linux/kvm.h b/include/linux/kvm.h
index 94540b3..deb9c38 100644
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h
@@ -234,6 +234,7 @@
 #define KVM_CAP_VAPIC 6
 #define KVM_CAP_EXT_CPUID 7
 #define KVM_CAP_CLOCKSOURCE 8
+#define KVM_CAP_NR_VCPUS 9       /* returns max vcpus per vm */
 
 /*
  * ioctls for VM fds