Subject: Re: [V2 PATCH 0/6] x86, NMI: give NMI handler a face-lift
From: Peter Zijlstra <peterz@infradead.org>
To: Don Zickus <dzickus@redhat.com>
Cc: Jason Wessel <jason.wessel@windriver.com>, Ingo Molnar <mingo@elte.hu>,
        Robert Richter <robert.richter@amd.com>, ying.huang@intel.com,
        Andi Kleen <andi@firstfloor.org>, LKML <linux-kernel@vger.kernel.org>,
        Frederic Weisbecker <fweisbec@gmail.com>
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Date: Mon, 22 Nov 2010 15:29:29 +0100
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On Mon, 2010-11-22 at 09:22 -0500, Don Zickus wrote:
> > > +static bool check_hw_exists(void)
> > > +{
> > > +       u64 val, val_new;
> > > +
> > > +       val = 0xabcdUL;
> > > +       (void) checking_wrmsrl(x86_pmu.perfctr, val);
> > > +       rdmsrl(x86_pmu.perfctr, val_new);
> > 
> > 
> > Yeah, this looks about right, although for extreme prudence I'd also
> use
> > a checking_rdmsrl().
> 
> I didn't realize such a function existed, I'll look into it.

yeah, the msr functions are a bit of a mess, but I think its called
something like rdmsrl_safe()
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