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authorVitaly Kuznetsov <vkuznets@redhat.com>2016-12-07 14:53:12 -0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-01-10 21:46:41 +0100
commit523b94087078f7f5ac10b7d9cd04277927031c39 (patch)
tree767861d57a51f2da5dd845d2905d18e9f3550193 /drivers/hv/hv.c
parent76d36ab79820430f73c584673aef10ba2446fced (diff)
downloadlinux-523b94087078f7f5ac10b7d9cd04277927031c39.tar.bz2
hv: make CPU offlining prevention fine-grained
Since commit e513229b4c38 ("Drivers: hv: vmbus: prevent cpu offlining on newer hypervisors") cpu offlining was disabled. It is still true that we can't offline CPUs which have VMBus channels bound to them but we may have 'free' CPUs (e.v. we booted with maxcpus= parameter and onlined CPUs after VMBus was initialized), these CPUs may be disabled without issues. In future, we may even allow closing CPUs which have only sub-channels assinged to them by closing these sub-channels. All devices will continue to work. 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>
Diffstat (limited to 'drivers/hv/hv.c')
-rw-r--r--drivers/hv/hv.c31
1 files changed, 31 insertions, 0 deletions
diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
index 8dbbed4efa45..714e1ebc834c 100644
--- a/drivers/hv/hv.c
+++ b/drivers/hv/hv.c
@@ -587,10 +587,41 @@ int hv_synic_cleanup(unsigned int cpu)
union hv_synic_simp simp;
union hv_synic_siefp siefp;
union hv_synic_scontrol sctrl;
+ struct vmbus_channel *channel, *sc;
+ bool channel_found = false;
+ unsigned long flags;
if (!hv_context.synic_initialized)
return -EFAULT;
+ /*
+ * Search for channels which are bound to the CPU we're about to
+ * cleanup. In case we find one and vmbus is still connected we need to
+ * fail, this will effectively prevent CPU offlining. There is no way
+ * we can re-bind channels to different CPUs for now.
+ */
+ mutex_lock(&vmbus_connection.channel_mutex);
+ list_for_each_entry(channel, &vmbus_connection.chn_list, listentry) {
+ if (channel->target_cpu == cpu) {
+ channel_found = true;
+ break;
+ }
+ spin_lock_irqsave(&channel->lock, flags);
+ list_for_each_entry(sc, &channel->sc_list, sc_list) {
+ if (sc->target_cpu == cpu) {
+ channel_found = true;
+ break;
+ }
+ }
+ spin_unlock_irqrestore(&channel->lock, flags);
+ if (channel_found)
+ break;
+ }
+ mutex_unlock(&vmbus_connection.channel_mutex);
+
+ if (channel_found && vmbus_connection.conn_state == CONNECTED)
+ return -EBUSY;
+
/* Turn off clockevent device */
if (ms_hyperv.features & HV_X64_MSR_SYNTIMER_AVAILABLE) {
clockevents_unbind_device(hv_context.clk_evt[cpu], cpu);