X86-MCE: fix a bug of xen-mceinj tool

Fix a bug of xen-mceinj tool which used to test mce by software way.

Signed-off-by: Liu, Jinsong <jinsong.liu@intel.com>
Committed-by: Keir Fraser <keir@xen.org>

tools/tests/mce-test/tools/xen-mceinj.c

@@ -134,8 +134,12 @@ static int mca_cpuinfo(xc_interface *xc_handle)
 {
     struct xen_mc mc;
 
+    memset(&mc, 0, sizeof(struct xen_mc));
+
     mc.cmd = XEN_MC_physcpuinfo;
-    if (xc_mca_op(xc_handle, &mc))
+    mc.interface_version = XEN_MCA_INTERFACE_VERSION;
+
+    if (!xc_mca_op(xc_handle, &mc))
         return mc.u.mc_physcpuinfo.ncpus;
     else
         return 0;