linux-kernel - Re: [tip:perfcounters/core] perf_counter, x86: remove X86_FEATURE_ARCH

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Message-ID: <20090511120514.GA13954@elte.hu>
Date:	Mon, 11 May 2009 14:05:14 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Jaswinder Singh Rajput <jaswinder@...nel.org>
Cc:	mingo@...hat.com, hpa@...or.com, paulus@...ba.org,
	linux-kernel@...r.kernel.org, robert.richter@....com,
	a.p.zijlstra@...llo.nl, tglx@...utronix.de,
	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:perfcounters/core] perf_counter, x86: remove
	X86_FEATURE_ARCH_PERFMON flag for AMD cpus


* Jaswinder Singh Rajput <jaswinder@...nel.org> wrote:

> On Mon, 2009-05-11 at 12:02 +0200, Ingo Molnar wrote:
> > * Jaswinder Singh Rajput <jaswinder@...nel.org> wrote:
> > 
> > > There is one more way to check performance monitor support for 
> > > Intel by using IA32_MISC_ENABLE MSR (0x1A0) bit 7 tells whether 
> > > performance monitoring is available or not.
> > > 
> > > But IA32_MISC_ENABLE MSR (0x1A0) is not available for Pentium and 
> > > P6.
> > > 
> > > So better I will add new cpufeature for performance monitoring for 
> > > x86:
> > > 
> > > X86_FEATURE_PERFMON : Performance monitor support
> > 
> > What is the exact wording of IA32_MISC_ENABLE bit 7 in the Intel 
> > documents?
> > 
> 
> Bit 7: Performance Monitoring Available. (R)
>        1 = Performance monitoring enabled
>        0 = Performance monitoring disabled

i guess, if 'perfmon' is not used yet ('arch_perfmon' is), we could 
add this as a separate, new cpu features flag.

Although the confusion factor is high ...

	Ingo
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