linux-kernel - Re: [PATCH] x86: Clean up files of Intel Processor Trace

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Message-ID: <20150803090807.GG25159@twins.programming.kicks-ass.net>
Date:	Mon, 3 Aug 2015 11:08:07 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc:	Takao Indoh <indou.takao@...fujitsu.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	linux-kernel@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH] x86: Clean up files of Intel Processor Trace

On Mon, Aug 03, 2015 at 12:03:13PM +0300, Alexander Shishkin wrote:
> Takao Indoh <indou.takao@...fujitsu.com> writes:

> Even though TOPA_SHIFT happens to be the same as PAGE_SHIFT, it is a
> property of a separate hardware block, not mmu. PAGE_SHIFT is 12, but
> 12 is not always PAGE_SHIFT.

PAGE_SHIFT is _always_ 12 on x86. Changing that will require changing
the page table format, a rather unlikely thing to go happen.

> > diff --git a/arch/x86/kernel/cpu/perf_event_intel_pt.c b/arch/x86/kernel/cpu/perf_event_intel_pt.c
> > index 183de71..1e7d89e 100644
> > --- a/arch/x86/kernel/cpu/perf_event_intel_pt.c
> > +++ b/arch/x86/kernel/cpu/perf_event_intel_pt.c
> > @@ -37,9 +37,9 @@ static struct pt_pmu pt_pmu;
> >  
> >  enum cpuid_regs {
> >  	CR_EAX = 0,
> > +	CR_EBX,
> >  	CR_ECX,
> > -	CR_EDX,
> > -	CR_EBX
> > +	CR_EDX
> >  };
> 
> This doesn't seem necessary.

For those of us suffering OCDs and all, its a good change though. The
alfabet song does go: A, B, C, D etc.. after all. Not: A, C, D, B ...
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