Drivers: hv: Check message and event pages for non-NULL before iounmap()

It might happen that some hyp SynIC pages aren't allocated.

Check for that and only then call iounmap().

Signed-off-by: Roman Kisel <romank@linux.microsoft.com>
Reviewed-by: Tianyu Lan <tiala@microsoft.com>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
Signed-off-by: Wei Liu <wei.liu@kernel.org>

Author: romank-msft

drivers/hv/hv.c

@@ -371,8 +371,10 @@ void hv_synic_disable_regs(unsigned int cpu)
 	 */
 	simp.simp_enabled = 0;
 	if (ms_hyperv.paravisor_present || hv_root_partition()) {
-		iounmap(hv_cpu->hyp_synic_message_page);
-		hv_cpu->hyp_synic_message_page = NULL;
+		if (hv_cpu->hyp_synic_message_page) {
+			iounmap(hv_cpu->hyp_synic_message_page);
+			hv_cpu->hyp_synic_message_page = NULL;
+		}
 	} else {
 		simp.base_simp_gpa = 0;
 	}
@@ -383,8 +385,10 @@ void hv_synic_disable_regs(unsigned int cpu)
 	siefp.siefp_enabled = 0;
 
 	if (ms_hyperv.paravisor_present || hv_root_partition()) {
-		iounmap(hv_cpu->hyp_synic_event_page);
-		hv_cpu->hyp_synic_event_page = NULL;
+		if (hv_cpu->hyp_synic_event_page) {
+			iounmap(hv_cpu->hyp_synic_event_page);
+			hv_cpu->hyp_synic_event_page = NULL;
+		}
 	} else {
 		siefp.base_siefp_gpa = 0;
 	}