Re: [Xen-devel] [PATCH 1/2] mwait_idle: Disable Baytrail Core and Module C6 auto-demotion

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 08.09.14 at 16:02, <ross.lagerwall@xxxxxxxxxx> wrote:
> On 09/08/2014 02:22 PM, Jan Beulich wrote:
>>>>> On 08.09.14 at 14:42, <ross.lagerwall@xxxxxxxxxx> wrote:
>>> From: Len Brown <len.brown@xxxxxxxxx>
>>>
>>> Power efficiency improves on Baytrail (Intel Atom Processor E3000)
>>> when C6 auto-demotion is disabled.
>>>
>>> Based on work by Srinidhi Kasagar <srinidhi.kasagar@xxxxxxxxx>.
>>>
>>> Signed-off-by: Len Brown <len.brown@xxxxxxxxx>
>>> Signed-off-by: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
>>
>> So we raced on pulling these over - I did so late last week too and
>> just didn't get to send them out yet. On this one I in fact doubt
>> (and sent a respective query to Len; no response yet) that the MSR
>> handling is. Hence my ported over patch is a little different:
>>
> 
> According to Intel's manual, those two registers have package scope, 
> i.e. all processor cores in the package share the same MSR, so 
> presumably the original commit is OK.

Provided none of these can occur in multi-socket systems (which
seems likely to be the case for Atoms, but I'm not finally certain,
and there's definitely no harm in doing this redundantly).

Jan


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