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

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Message-ID: <AANLkTi=Vvi7MBbmnT7-iuLOBH4_zBzirmBt3sjwqyhmZ@mail.gmail.com>
Date:	Tue, 23 Nov 2010 19:37:21 +0100
From:	Sedat Dilek <sedat.dilek@...glemail.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Don Zickus <dzickus@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86, perf, nmi: Disable perf if counters are not accessable

On Tue, Nov 23, 2010 at 7:29 PM, Sedat Dilek <sedat.dilek@...glemail.com> wrote:
> On Tue, Nov 23, 2010 at 7:27 PM, Peter Zijlstra <peterz@...radead.org> wrote:
>> On Tue, 2010-11-23 at 19:21 +0100, Sedat Dilek wrote:
>>> 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.
>>
>> Have you tried booting with "lapic" as the second last msg suggests you
>> do?
>>
>
> Yes, I did try before there was [1], booting with "lapic" had no effect.
>
> - Sedat -
>
> [1] bugfix/x86/Skip-looking-for-ioapic-overrides-when-ioapics-are-not-present.patch
>

OK, some months went by when I last tested this option.

Now, with linux-next (next-20101123) things look better.

# cat /proc/cmdline
BOOT_IMAGE=/boot/vmlinuz-2.6.37-rc3-686
root=UUID=1ceb69a7-ecf4-47e9-a231-b74e0f0a9b62 ro radeon.modeset=1
lapic 3

# dmesg | egrep -i 'NMI|APIC'
[    0.000000] Using APIC driver default
[    0.000000] Local APIC disabled by BIOS -- reenabling.
[    0.000000] Found and enabled local APIC!
[    0.000000] Kernel command line:
BOOT_IMAGE=/boot/vmlinuz-2.6.37-rc3-686
root=UUID=1ceb69a7-ecf4-47e9-a231-b74e0f0a9b62 ro radeon.modeset=1
lapic 3
[    0.032158] Enabling APIC mode:  Flat.  Using 0 I/O APICs
[    0.036000] NMI watchdog enabled, takes one hw-pmu counter.

- Sedat -
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