Drivers: hv: restore hypervcall page cleanup before kexec

We need to cleanup the hypercall page before doing kexec/kdump or the new
kernel may crash if it tries to use it. Reuse the now-empty hv_cleanup
function renaming it to hyperv_cleanup and moving to the arch specific
code.

Fixes: 8730046c ("Drivers: hv vmbus: Move Hypercall page setup out of common code")
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

arch/x86/hyperv/hv_init.c

@@ -165,6 +165,22 @@ void hyperv_init(void)
 		clocksource_register_hz(&hyperv_cs_msr, NSEC_PER_SEC/100);
 }
 
+/*
+ * This routine is called before kexec/kdump, it does the required cleanup.
+ */
+void hyperv_cleanup(void)
+{
+	union hv_x64_msr_hypercall_contents hypercall_msr;
+
+	/* Reset our OS id */
+	wrmsrl(HV_X64_MSR_GUEST_OS_ID, 0);
+
+	/* Reset the hypercall page */
+	hypercall_msr.as_uint64 = 0;
+	wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
+}
+EXPORT_SYMBOL_GPL(hyperv_cleanup);
+
 /*
  * hv_do_hypercall- Invoke the specified hypercall
  */

arch/x86/include/asm/mshyperv.h

@@ -171,5 +171,6 @@ void hv_remove_crash_handler(void);
 void hyperv_init(void);
 void hyperv_report_panic(struct pt_regs *regs);
 bool hv_is_hypercall_page_setup(void);
+void hyperv_cleanup(void);
 #endif
 #endif

drivers/hv/hv.c

@@ -70,16 +70,6 @@ int hv_init(void)
 	return 0;
 }
 
-/*
- * hv_cleanup - Cleanup routine.
- *
- * This routine is called normally during driver unloading or exiting.
- */
-void hv_cleanup(bool crash)
-{
-
-}
-
 /*
  * hv_post_message - Post a message using the hypervisor message IPC.
  *

drivers/hv/hyperv_vmbus.h

@@ -255,8 +255,6 @@ struct hv_ring_buffer_debug_info {
 
 extern int hv_init(void);
 
-extern void hv_cleanup(bool crash);
-
 extern int hv_post_message(union hv_connection_id connection_id,
 			 enum hv_message_type message_type,
 			 void *payload, size_t payload_size);

drivers/hv/vmbus_drv.c

@@ -962,7 +962,7 @@ static int vmbus_bus_init(void)
 
 	ret = bus_register(&hv_bus);
 	if (ret)
-		goto err_cleanup;
+		return ret;
 
 	hv_setup_vmbus_irq(vmbus_isr);
 
@@ -1004,9 +1004,6 @@ static int vmbus_bus_init(void)
 
 	bus_unregister(&hv_bus);
 
-err_cleanup:
-	hv_cleanup(false);
-
 	return ret;
 }
 
@@ -1462,7 +1459,7 @@ static void hv_kexec_handler(void)
 	/* Make sure conn_state is set as hv_synic_cleanup checks for it */
 	mb();
 	cpuhp_remove_state(hyperv_cpuhp_online);
-	hv_cleanup(false);
+	hyperv_cleanup();
 };
 
 static void hv_crash_handler(struct pt_regs *regs)
@@ -1475,7 +1472,7 @@ static void hv_crash_handler(struct pt_regs *regs)
 	 */
 	vmbus_connection.conn_state = DISCONNECTED;
 	hv_synic_cleanup(smp_processor_id());
-	hv_cleanup(true);
+	hyperv_cleanup();
 };
 
 static int __init hv_acpi_init(void)
@@ -1535,7 +1532,6 @@ static void __exit vmbus_exit(void)
 						 &hyperv_panic_block);
 	}
 	bus_unregister(&hv_bus);
-	hv_cleanup(false);
 	for_each_online_cpu(cpu) {
 		tasklet_kill(hv_context.event_dpc[cpu]);
 	}