When adding cpuidle support to pSeries, we introduced two
regressions:
- The new cpuidle backend driver only works under hypervisors
supporting the "SLPLAR" option, which isn't the case of the
old POWER4 hypervisor and the HV "light" used on js2x blades
- The cpuidle driver registers fairly late, meaning that for
a significant portion of the boot process, we end up having
all threads spinning. This slows down the boot process and
increases the overall resource usage if the hypervisor has
shared processors.
This fixes both by implementing a "default" idle that will cede
to the hypervisor when possible, in a very simple way without
all the bells and whisles of cpuidle.
Reported-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
Acked-by: Deepthi Dharwar <deepthi@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
CC: <stable@vger.kernel.org>
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