linux-kernel - Re: [PATCH 2/15 -tip] x86: Add cpufeatures for Advanced Power Management

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Date:	Tue, 12 May 2009 06:01:04 +0530
From:	Jaswinder Singh Rajput <jaswinder@...nel.org>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	"H. Peter Anvin" <hpa@...nel.org>,
	Robert Richter <robert.richter@....com>,
	x86 maintainers <x86@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/15 -tip] x86: Add cpufeatures for Advanced Power
 Management

On Mon, 2009-05-11 at 21:09 +0200, Ingo Molnar wrote:
> * H. Peter Anvin <hpa@...or.com> wrote:
> 
> > Jaswinder Singh Rajput wrote:
> >> 1. Add Advanced Power Management (Function 8000_0007h), edx
> >> 2. unification of X86_FEATURE_CONSTANT_TSC (from intel.c, amd.c to common.c)
> >> 3. Remove cpu/powerflags.c
> >> 4. Remove x86_power
> >> 5. Move 'power management' to flags of /proc/cpuinfo
> >>
> >> /proc/cpuinfo (before)
> >> flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge
> >> mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt
> >> rdtscp lm 3dnowext 3dnow constant_tsc rep_good nonstop_tsc pni cx16
> >> lahf_lm cmp_legacy svm extapic cr8_legacy 3dnowprefetch osvw skinit pname
> >> ..
> >> power management: ts ttp tm stc 100mhzsteps hwpstate
> >>
> >> /proc/cpuinfo (after)
> >> flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge
> >> mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt
> >> rdtscp lm 3dnowext 3dnow rep_good tsc_reliable nonstop_tsc pni cx16
> >> lahf_lm cmp_legacy svm extapic cr8_legacy 3dnowprefetch osvw skinit pname
> >> ts ttp htc stc 100mhzsteps hwpstate constant_tsc
> >>
> >> Signed-off-by: Jaswinder Singh Rajput <jaswinderrajput@...il.com>
> >
> > NAK in the extreme.
> >
> > This is an incompatible change to a userspace visible API.  The 
> > fact that power management flags were separate was braindamage in 
> > the first place, of course, but we don't break established 
> > userspace APIs even if they're stupid.
> 
> Yes, and you pointed it out in an earlier reply.
> 
> Jaswinder, as hpa said it before, we only ever extend cpuflags (i.e. 
> add new ones mainly, and map new CPUs to the existing flags), but we 
> dont change their semantics.
> 

OK, then I will remove from this patch :

 3. Remove cpu/powerflags.c
 4. Remove x86_power
 5. Move 'power management' to flags of /proc/cpuinfo

--
JSR

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