linux-kernel - Re: [git-pull -tip] x86: cpu

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Date:	Wed, 29 Apr 2009 12:50:21 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Jaswinder Singh Rajput <jaswinder@...nel.org>
Cc:	x86 maintainers <x86@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>
Subject: Re: [git-pull -tip] x86: cpu_debug patches


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

> On Tue, 2009-04-28 at 19:28 +0200, Ingo Molnar wrote:
> > * Jaswinder Singh Rajput <jaswinder@...nel.org> wrote:
> > 
> > > @@ -850,10 +903,10 @@ static int cpu_init_cpu(void)
> > >  		cpui = &cpu_data(cpu);
> > >  		if (!cpu_has(cpui, X86_FEATURE_MSR))
> > >  			continue;
> > > -		per_cpu(cpu_model, cpu) = ((cpui->x86_vendor << 16) |
> > > -					   (cpui->x86 << 8) |
> > > -					   (cpui->x86_model));
> > > -		per_cpu(cpu_modelflag, cpu) = get_cpu_modelflag(cpu);
> > > +		per_cpu(cpu_modelflag, cpu) = get_cpu_flag(cpui);
> > > +		if (!per_cpu(cpu_modelflag, cpu))
> > > +			send_report(per_cpu(cpu_priv_count, cpu), cpui);
> > 
> > This means that if the CPU is not enumerated in the model table 
> > explicitly, we'll fall back to some really minimal output, right?
> > 
> 
> Yes.

That's a bug really: it means that for every new CPU type that comes 
around we need to update this code. I.e. precisely for those CPUs 
where we might need the most help from such a debug facility, we 
wont have much info to look at ... New CPUs generally support all 
the CPU features that are displayed here, in a compatible manner.

So that needs to be improved/changed to not be tied to such a static 
'cpu model' enumeration but instead be CPU feature flags driven. See 
all the existing cpu_has_*() tests we have.

	Ingo
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