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Message-ID: <4DA74E5D.4060002@openvz.org>
Date: Thu, 14 Apr 2011 23:43:25 +0400
From: Cyrill Gorcunov <gorcunov@openvz.org>
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To: Ingo Molnar <mingo@elte.hu>
CC: Don Zickus <dzickus@redhat.com>, Lin Ming <ming.m.lin@intel.com>,
        Shaun Ruffell <sruffell@digium.com>,
        Maciej Rutecki <maciej.rutecki@gmail.com>,
        Peter Zijlstra <a.p.zijlstra@chello.nl>,
        Stephane Eranian <eranian@google.com>,
        Robert Richter <robert.richter@amd.com>,
        lkml <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH -tip] perf, x86: fix unknown NMIs on a Pentium4 box
References: <4DA70950.3060102@openvz.org> <20110414174327.GA8863@elte.hu> <20110414183231.GN16939@redhat.com> <20110414184606.GD16064@elte.hu>
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On 04/14/2011 10:46 PM, Ingo Molnar wrote:
> 
> btw., the bug went away once i removed your patch so it's 100% sure caused by 
> this change.
> 
> Thanks,
> 
> 	Ingo

Ingo if you have a chance mind to give this patch a shot please? Seems we might miss unmasking
for inflight nmis.
-- 
Index: linux-2.6.git/arch/x86/kernel/cpu/perf_event.c
=====================================================================
--- linux-2.6.git.orig/arch/x86/kernel/cpu/perf_event.c
+++ linux-2.6.git/arch/x86/kernel/cpu/perf_event.c
@@ -1365,14 +1365,15 @@ perf_event_nmi_handler(struct notifier_b
 		 * will be empty and daze the CPU. So, we drop it to
 		 * avoid false-positive 'unknown nmi' messages.
 		 */
+		apic_write(APIC_LVTPC, APIC_DM_NMI);
 		return NOTIFY_STOP;
 	default:
 		return NOTIFY_DONE;
 	}

-	apic_write(APIC_LVTPC, APIC_DM_NMI);

 	handled = x86_pmu.handle_irq(args->regs);
+	apic_write(APIC_LVTPC, APIC_DM_NMI);
 	if (!handled)
 		return NOTIFY_DONE;