Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756215AbcJ1L1M (ORCPT ); Fri, 28 Oct 2016 07:27:12 -0400 Received: from atrey.karlin.mff.cuni.cz ([195.113.26.193]:58983 "EHLO atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752074AbcJ1L1L (ORCPT ); Fri, 28 Oct 2016 07:27:11 -0400 Date: Fri, 28 Oct 2016 13:27:08 +0200 From: Pavel Machek To: Peter Zijlstra Cc: Ingo Molnar , Kees Cook , Arnaldo Carvalho de Melo , kernel list , Ingo Molnar , Alexander Shishkin , "kernel-hardening@lists.openwall.com" Subject: Re: rowhammer protection [was Re: Getting interrupt every million cache misses] Message-ID: <20161028112707.GB5635@amd> References: <20161026204748.GA11177@amd> <20161027082801.GE3568@worktop.programming.kicks-ass.net> <20161027091104.GB19469@amd> <20161027093334.GK3102@twins.programming.kicks-ass.net> <20161027212747.GA18147@amd> <20161028070701.GA11376@gmail.com> <20161028085039.GA15032@amd> <20161028090423.GY3102@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="gatW/ieO32f1wygP" Content-Disposition: inline In-Reply-To: <20161028090423.GY3102@twins.programming.kicks-ass.net> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1426 Lines: 49 --gatW/ieO32f1wygP Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable 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. >=20 > 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 --=20 (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blo= g.html --gatW/ieO32f1wygP Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iEYEARECAAYFAlgTNgsACgkQMOfwapXb+vJQVACdEnUaKPJsS465Ht/EPS2Ak6nZ 548AnRa6MSiB7zItnc4TJcLTTBQPy2x6 =rR+o -----END PGP SIGNATURE----- --gatW/ieO32f1wygP--