linux-kernel - Re: rowhammer protection [was Re: Getting interrupt every million cache misses]

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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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