linux-kernel - Re: A question of perf NMI handler

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: <20100804154552.GR3353@redhat.com>
Date:	Wed, 4 Aug 2010 11:45:52 -0400
From:	Don Zickus <dzickus@...hat.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Robert Richter <robert.richter@....com>,
	Lin Ming <ming.m.lin@...el.com>, Ingo Molnar <mingo@...e.hu>,
	Cyrill Gorcunov <gorcunov@...il.com>,
	"fweisbec@...il.com" <fweisbec@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Huang, Ying" <ying.huang@...el.com>
Subject: Re: A question of perf NMI handler

On Wed, Aug 04, 2010 at 05:02:41PM +0200, Peter Zijlstra wrote:
> So then the first interrupt will see 3+ overflows, return 3+, and will
> thus eat 2+ NMIs, only one of which will be the pending interrupt,
> leaving 1+ NMIs from other sources to consume unhandled.
> 
> In which case Yinghai will have to press his NMI button 2+ times before
> it registers.
> 
> That said, that might be a better situation than always consuming
> unknown NMIs.. 

Well if the worse case scenario is only one extra NMI, then I can change
the logic in my patch to eat a max of 1 possible NMI instead of 2 as in the
example you gave above.

It still won't be 100% accurate but how often are people running perf
where they need 4 counters, have to hit an external nmi button or run into
broken firmware all at the same time? :-)

Cheers,
Don

--
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/