x86, hotplug: Use mwait to offline a processor, fix the legacy case
The code in native_play_dead() has a number of problems: 1. We should use MWAIT when available, to put ourselves into a deeper sleep state. 2. We use the existence of CLFLUSH to determine if WBINVD is safe, but that is totally bogus -- WBINVD is 486+, whereas CLFLUSH is a much later addition. 3. We should do WBINVD inside the loop, just in case of something like setting an A bit on page tables. Pointed out by Arjan van de Ven. This code is based in part of a previous patch by Venki Pallipadi, but unlike that patch this one keeps all the detection code local instead of pre-caching a bunch of information. We're shutting down the CPU; there is absolutely no hurry. This patch moves all the code to C and deletes the global wbinvd_halt() which is broken anyway. Originally-by:Venkatesh Pallipadi <venkatesh.pallipadi@intel.com> Signed-off-by:
H. Peter Anvin <hpa@linux.intel.com> Reviewed-by:
Arjan van de Ven <arjan@linux.intel.com> Cc: Len Brown <lenb@kernel.org> Cc: Venkatesh Pallipadi <venki@google.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.hl> LKML-Reference: <20090522232230.162239000@intel.com>
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