linux-kernel - Re: [PATCH -v3] perf, x86: try to handle unknown nmis with running perfctrs

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20100827075132.GD22783@erda.amd.com>
Date:	Fri, 27 Aug 2010 09:51:32 +0200
From:	Robert Richter <robert.richter@....com>
To:	Don Zickus <dzickus@...hat.com>
CC:	Ingo Molnar <mingo@...e.hu>, Peter Zijlstra <peterz@...radead.org>,
	Cyrill Gorcunov <gorcunov@...il.com>,
	Lin Ming <ming.m.lin@...el.com>,
	"fweisbec@...il.com" <fweisbec@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Huang, Ying" <ying.huang@...el.com>,
	Yinghai Lu <yinghai@...nel.org>,
	Andi Kleen <andi@...stfloor.org>
Subject: Re: [PATCH -v3] perf, x86: try to handle unknown nmis with running
 perfctrs

On 26.08.10 17:14:24, Don Zickus wrote:
> diff --git a/arch/x86/kernel/cpu/perf_event_intel.c b/arch/x86/kernel/cpu/perf_event_intel.c
> index 4539b4b..d16ebd8 100644
> --- a/arch/x86/kernel/cpu/perf_event_intel.c
> +++ b/arch/x86/kernel/cpu/perf_event_intel.c
> @@ -738,6 +738,7 @@ again:
>  
>  	inc_irq_stat(apic_perf_irqs);
>  	ack = status;
> +	intel_pmu_ack_status(ack);

Yes, not immediately ack'ing the status was suspect to me too. Though
it must then be the same counter that retriggers. Or, it is a cpu
bug. You could add a debug print of the status register for the case
the loop is reentered, would be interesting...

Thank for fixing this.

-Robert

>  
>  	intel_pmu_lbr_read();
>  
> @@ -766,8 +767,6 @@ again:
>  			x86_pmu_stop(event);
>  	}
>  
> -	intel_pmu_ack_status(ack);
> -
>  	/*
>  	 * Repeat if there is more work to be done:
>  	 */
> 

-- 
Advanced Micro Devices, Inc.
Operating System Research Center

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/