On Wed, May 28, 2014 at 10:08:56AM +0530, Preeti U Murthy wrote:

From: Srivatsa S. Bhat <redacted>

The offline cpus are put to fast sleep if the idle state is discovered in the
device tree. This is to gain maximum powersavings in the offline state.

...

 	while (!generic_check_cpu_restart(cpu)) {
 		ppc64_runlatch_off();
-		power7_nap();
+
+		/* If sleep is supported, go to sleep, instead of nap */
+		if (idle_states & IDLE_USE_SLEEP)
+			power7_sleep();
+		else
+			power7_nap();
+
 		ppc64_runlatch_on();
 		if (!generic_check_cpu_restart(cpu)) {
 			DBG("CPU%d Unexpected exit while offline !\n", cpu);

What is the latency for waking up from fast sleep state?  I'm concerned
this will increase the latency for entering KVM guests.

Paul.