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Message-ID: <20161028112707.GB5635@amd>
Date: Fri, 28 Oct 2016 13:27:08 +0200
From: Pavel Machek <pavel@....cz>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Ingo Molnar <mingo@...nel.org>, Kees Cook <keescook@...omium.org>,
Arnaldo Carvalho de Melo <acme@...hat.com>,
kernel list <linux-kernel@...r.kernel.org>,
Ingo Molnar <mingo@...hat.com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
"kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>
Subject: Re: rowhammer protection [was Re: Getting interrupt every million
cache misses]
Hi!
> > I agree this needs to be tunable (and with the other suggestions). But
> > this is actually not the most important tunable: the detection
> > threshold (rh_attr.sample_period) should be way more important.
>
> So being totally ignorant of the detail of how rowhammer abuses the DDR
> thing, would it make sense to trigger more often and delay shorter? Or
> is there some minimal delay required for things to settle or
> something.
We can trigger more often and delay shorter, but it will mean that
protection will trigger with more false positives. I guess I'll play
with constants too see how big the effect is.
BTW...
[ 6267.180092] INFO: NMI handler (perf_event_nmi_handler) took too
long to run: 63.501 msecs
but I'm doing mdelay(64). .5 msec is not big difference, but...
Best regards,
Pavel
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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