linux-kernel - Re: [PATCH] x86, perf, nmi: Disable perf if counters are not accessable

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Date:	Tue, 23 Nov 2010 19:21:27 +0100
From:	Sedat Dilek <sedat.dilek@...glemail.com>
To:	Don Zickus <dzickus@...hat.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH] x86, perf, nmi: Disable perf if counters are not accessable

On Tue, Nov 23, 2010 at 5:56 PM, Don Zickus <dzickus@...hat.com> wrote:
> On Tue, Nov 23, 2010 at 04:15:05PM +0100, Sedat Dilek wrote:
>> Hi,
>>
>> I am seeing for a while this warning in my system-wide logs:
>>
>> Nov 23 11:54:14 tbox kernel: [    0.040335] NMI watchdog failed to
>> create perf event on cpu0: ffffffa1
>>
>> As I saw this patch from [1], I was hoping it's also fixing my problem
>> on an Intel Pentium-M (Banias) Single-Core CPU:
>
> I doubt it.  This patch was intended for virtualization where the perf
> counters are not emulated but the perf subsystem didn't know that.
>
> Your error code is 'ffffffa1'.  That translates to EOPNOTSUPP.  The only
> place I can see where that is returned is if your system does not have a
> local apic on it (as set by the cpu feature bits).
>

The problem still remains with your original patch [1] and Peter's
followup patch (is attached)

Due to BIOS l(ocal)apic is not possible:

# dmesg | grep -i apic
[    0.000000] Using APIC driver default
[    0.000000] Local APIC disabled by BIOS -- you can enable it with "lapic"
[    0.000000] APIC: disable apic facility
[    0.000000] APIC: switched to apic NOOP
[    0.008891] no APIC, boot with the "lapic" boot parameter to force-enable it.
[    0.036141] Local APIC not detected. Using dummy APIC emulation.

> Applying this patch may still get you the same result because the perf
> counters might be there but there is no local apic to deliver the
> interrupts.
>
> I would have to see in your log file the output starting at the line with
>
> Performance Events:
>
> and pasting the next dozen lines or so to have a better understanding what
> is going on.  Or you can just attach the whole log in your reply.
>
> Cheers,
> Don
>

Full dmesg is attached.

- Sedat -

[1] https://patchwork.kernel.org/patch/348341/

View attachment "dmesg.txt" of type "text/plain" (54994 bytes)

View attachment "x86-perf-nmi-Disable-perf-if-counters-are-not-accessable-followup-patch-by-peter-zijlstra.patch" of type "text/x-diff" (635 bytes)