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

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Message-ID: <4CE708AA.7030405@windriver.com>
Date:	Fri, 19 Nov 2010 17:30:50 -0600
From:	Jason Wessel <jason.wessel@...driver.com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	Don Zickus <dzickus@...hat.com>, 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 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>

Thanks,
Jason.
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