Drivers: hv: vmbus: Teardown clockevent devices on module unload

Newly introduced clockevent devices made it impossible to unload hv_vmbus
module as clockevents_config_and_register() takes additional reverence to
the module. To make it possible again we do the following:
- avoid setting dev->owner for clockevent devices;
- implement hv_synic_clockevents_cleanup() doing clockevents_unbind_device();
- call it from vmbus_exit().

In theory hv_synic_clockevents_cleanup() can be merged with hv_synic_cleanup(),
however, we call hv_synic_cleanup() from smp_call_function_single() and this
doesn't work for clockevents_unbind_device() as it does such call on its own. I
opted for a separate function.

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>

3 files changed, 27 insertions, 1 deletions

diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
index 39531dcf582f..d3943bceecc3 100644
--- a/drivers/hv/hv.c
+++ b/drivers/hv/hv.c
@@ -312,7 +312,11 @@ static void hv_init_clockevent_device(struct clock_event_device *dev, int cpu)
         dev->features = CLOCK_EVT_FEAT_ONESHOT;
         dev->cpumask = cpumask_of(cpu);
         dev->rating = 1000;
-        dev->owner = THIS_MODULE;
+        /*
+         * Avoid settint dev->owner = THIS_MODULE deliberately as doing so will
+         * result in clockevents_config_and_register() taking additional
+         * references to the hv_vmbus module making it impossible to unload.
+         */
 
         dev->set_mode = hv_ce_setmode;
         dev->set_next_event = hv_ce_set_next_event;
@@ -470,6 +474,20 @@ void hv_synic_init(void *arg)
 }
 
 /*
+ * hv_synic_clockevents_cleanup - Cleanup clockevent devices
+ */
+void hv_synic_clockevents_cleanup(void)
+{
+        int cpu;
+
+        if (!(ms_hyperv.features & HV_X64_MSR_SYNTIMER_AVAILABLE))
+                return;
+
+        for_each_online_cpu(cpu)
+                clockevents_unbind_device(hv_context.clk_evt[cpu], cpu);
+}
+
+/*
  * hv_synic_cleanup - Cleanup routine for hv_synic_init().
  */
 void hv_synic_cleanup(void *arg)
@@ -483,6 +501,11 @@ void hv_synic_cleanup(void *arg)
         if (!hv_context.synic_initialized)
                 return;
 
+        /* Turn off clockevent device */
+        if (ms_hyperv.features & HV_X64_MSR_SYNTIMER_AVAILABLE)
+                hv_ce_setmode(CLOCK_EVT_MODE_SHUTDOWN,
+                              hv_context.clk_evt[cpu]);
+
         rdmsrl(HV_X64_MSR_SINT0 + VMBUS_MESSAGE_SINT, shared_sint.as_uint64);
 
         shared_sint.masked = 1;
diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
index 6cf2de9f487a..b055e53bbc6e 100644
--- a/drivers/hv/hyperv_vmbus.h
+++ b/drivers/hv/hyperv_vmbus.h
@@ -572,6 +572,8 @@ extern void hv_synic_init(void *irqarg);
 
 extern void hv_synic_cleanup(void *arg);
 
+extern void hv_synic_clockevents_cleanup(void);
+
 /*
  * Host version information.
  */
diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index d8233d4513a5..6d99aa5c49d6 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -1032,6 +1032,7 @@ static void __exit vmbus_exit(void)
         int cpu;
 
         vmbus_connection.conn_state = DISCONNECTED;
+        hv_synic_clockevents_cleanup();
         hv_remove_vmbus_irq();
         vmbus_free_channels();
         bus_unregister(&hv_bus);