linux-kernel - Re: [V2 PATCH 0/6] x86, NMI: give NMI handler a face-lift

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Date:	Mon, 22 Nov 2010 09:22:37 -0500
From:	Don Zickus <dzickus@...hat.com>
To:	Jason Wessel <jason.wessel@...driver.com>
Cc:	Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...e.hu>,
	Robert Richter <robert.richter@....com>, ying.huang@...el.com,
	Andi Kleen <andi@...stfloor.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Frederic Weisbecker <fweisbec@...il.com>
Subject: Re: [V2 PATCH 0/6] x86, NMI: give NMI handler a face-lift

On Fri, Nov 19, 2010 at 05:30:50PM -0600, Jason Wessel wrote:
> On 11/19/2010 05:09 PM, Peter Zijlstra wrote:
> > On Fri, 2010-11-19 at 17:59 -0500, Don Zickus wrote:
> >> 
> >> @@ -1371,6 +1385,12 @@ void __init init_hw_perf_events(void)
> >> 
> >>         pmu_check_apic();
> >> 
> >> +       /* sanity check that the hardware exists or is emulated */
> >> +       if (!check_hw_exists()) {
> >> +               pr_cont("no PMU driver, software events only.\n");
> >> +               return;
> >> +       }
> >
> > Maybe report something like this:
> >   "Broken PMU hardware detected, software events only."
> >
> > Because this is really not something that's supposed to happen.
> 
> The kgdb test suite is passing with Don's perf detect logic, so we are
> back to good.  I am in agreement with Peter about the message
> indicating that it is broken hardware.  We don't in any way shape or
> form want leave the illusion this works in the VM.
> 
> # dmesg |grep Per
> <6>Performance Events: no PMU driver, software events only.
> 
> 
> Tested on qemu and kvm, several revisions worth, because it is all
> automated.
> 
> Tested-by: Jason Wessel <jason.wessel@...driver.com>

Awesome.  Thanks for the quick testing Jason.

Cheers,.
Don
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