hv: change clockevents unbind tactics

To get prepared to CPU offlining support we need co change the way how we
unbind clockevent devices. As one CPU may go online/offline multiple times
we need to bind it in hv_synic_init() and unbind it in hv_synic_cleanup().
There is an additional corner case: when we unload the module completely we
need to switch to some other clockevent mechanism before stopping VMBus or
we will hang. We can't call hv_synic_cleanup() before unloading VMBus as
we won't be able to send UNLOAD request and get a response so
hv_synic_clockevents_cleanup() has to live. Luckily, we can always call
clockevents_unbind_device(), even if it wasn't bound before and there is
no issue if we call it twice.

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>

diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
index 60dbd6cb4640cd6caeb36a8c07585660d812f3b9..446802ae8f1bc6b72f41b468ee9e32c145378fb3 100644 (file)
--- a/drivers/hv/hv.c
+++ b/drivers/hv/hv.c
@@ -575,7 +575,7 @@ void hv_synic_clockevents_cleanup(void)
        if (!(ms_hyperv.features & HV_X64_MSR_SYNTIMER_AVAILABLE))
                return;
 
-       for_each_online_cpu(cpu)
+       for_each_present_cpu(cpu)
                clockevents_unbind_device(hv_context.clk_evt[cpu], cpu);
 }
 
@@ -594,8 +594,10 @@ void hv_synic_cleanup(void *arg)
                return;
 
        /* Turn off clockevent device */
-       if (ms_hyperv.features & HV_X64_MSR_SYNTIMER_AVAILABLE)
+       if (ms_hyperv.features & HV_X64_MSR_SYNTIMER_AVAILABLE) {
+               clockevents_unbind_device(hv_context.clk_evt[cpu], cpu);
                hv_ce_shutdown(hv_context.clk_evt[cpu]);
+       }
 
        rdmsrl(HV_X64_MSR_SINT0 + VMBUS_MESSAGE_SINT, shared_sint.as_uint64);