kexec: don't initialize when no crash area was reserved

While the waste of memory needed may not be significant, the amount of
additional but pointless entries in /proc/iomem certainly may be (on
large systems).

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/drivers/xen/core/machine_kexec.c
+++ b/drivers/xen/core/machine_kexec.c
@@ -34,6 +34,17 @@ void __init xen_machine_kexec_setup_reso
 	if (!is_initial_xendomain())
 		return;
 
+	/* fill in crashk_res if range is reserved by hypervisor */
+	memset(&range, 0, sizeof(range));
+	range.range = KEXEC_RANGE_MA_CRASH;
+
+	if (HYPERVISOR_kexec_op(KEXEC_CMD_kexec_get_range, &range)
+	    || !range.size)
+		return;
+
+	crashk_res.start = range.start;
+	crashk_res.end = range.start + range.size - 1;
+
 	/* determine maximum number of physical cpus */
 	op.cmd = XENPF_get_cpuinfo;
 	op.u.pcpu_info.xen_cpuid = 0;
@@ -96,19 +107,6 @@ void __init xen_machine_kexec_setup_reso
 	xen_hypervisor_res.end = range.start + range.size - 1;
 	xen_hypervisor_res.flags = IORESOURCE_BUSY | IORESOURCE_MEM;
 
-	/* fill in crashk_res if range is reserved by hypervisor */
-
-	memset(&range, 0, sizeof(range));
-	range.range = KEXEC_RANGE_MA_CRASH;
-
-	if (HYPERVISOR_kexec_op(KEXEC_CMD_kexec_get_range, &range))
-		goto free;
-
-	if (range.size) {
-		crashk_res.start = range.start;
-		crashk_res.end = range.start + range.size - 1;
-	}
-
 	/* get physical address of vmcoreinfo */
 	memset(&range, 0, sizeof(range));
 	range.range = KEXEC_RANGE_MA_VMCOREINFO;