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

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Message-ID: <4A086AB2.7010309@zytor.com>
Date:	Mon, 11 May 2009 11:13:06 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Jaswinder Singh Rajput <jaswinder@...nel.org>
CC:	Ingo Molnar <mingo@...e.hu>, "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

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.

	-hpa
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