Re: [PATCH 1/2] x86: fix keeping track of AMD C1E

["H. Peter Anvin" <hpa@zytor.com>]

On 07/16/2010 09:25 AM, Borislav Petkov wrote:
> 
> I don't see the need for two things denoting C1E for the very simple
> reason: when C1E gets enabled on a machine, one of the bits gets set in
> the MSR on each core simultaneously. So if one core sees one of the bits
> set, all the remaining cores are seeing them too. The first core that
> sees one of the bits in the MSR, sets c1e_detected.
> 
> So next time any core does cpu_idle() => c1e_idle(), it switches to
> timer broadcast on it since it might go into C1E if all the others
> follow.
> 
> Frankly, I can't think of a case where we'd need to two things - I
> could be missing something. But this workaround is a couple of years
> old, maybe Thomas might give us more insight into whether there's a
> particular reason for the cpuid flag and the c1e_detected variable.
> Thomas?
> 

I'm not saying there should be two things (and that's clearly wrong no
matter what), but rather it's not clear to me that the one thing should
be a variable.

	-hpa