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Liu, Jinsong authored
Play dead is a fragile and tricky point of cpu offline logic. For how to play cpu dead, linux kernel changed several times: Very old kernel support 3 ways to play cpu dead: mwait, SYSIO, and halt, just like what cpuidle did when enter C3; Later, it cancel mwait and SYSIO support, only use halt to play dead; Latest linux 2.6.38 add mwait support when cpu dead. This patch cancel SYSIO method when cpu dead, keep same with latest kernel. SYSIO is an obsoleted method to enter deep C, with some tricky hardware behavior, and seldom supported in new platform. Xen experiment indicate that when cpu dead, SYSIO method would trigger unknown issue which would bring strange error. We now cancel SYSIO method when cpu dead, after all, correctness is more important than power save, and btw new platform use mwait. Signed-off-by: Liu, Jinsong <jinsong.liu@intel.com>
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