From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752796AbbC0Mha (ORCPT ); Fri, 27 Mar 2015 08:37:30 -0400 Received: from mail.skyhub.de ([78.46.96.112]:33060 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752501AbbC0Mh1 (ORCPT ); Fri, 27 Mar 2015 08:37:27 -0400 Date: Fri, 27 Mar 2015 13:35:38 +0100 From: Borislav Petkov To: Ingo Molnar Cc: Hector Marco-Gisbert , linux-kernel@vger.kernel.org, akpm@linux-foundation.org, Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , x86@kernel.org, Alexander Viro , Jan-Simon , linux-fsdevel@vger.kernel.org, kees Cook , Ismael Ripoll Subject: Re: [PATCH] mm/x86: AMD Bulldozer ASLR fix Message-ID: <20150327123537.GB18912@pd.tnic> References: <20150326190800.GF27751@pd.tnic> <1427456301-3764-1-git-send-email-hecmargi@upv.es> <20150327121448.GB15631@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20150327121448.GB15631@gmail.com> 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 On Fri, Mar 27, 2015 at 01:14:48PM +0100, Ingo Molnar wrote: > It's not a bug, it's a feature: to work around a Bulldozer cache > aliasing performance problem we have to keep bits 12,13,14 equal for > all mappings in the system. > > Your patch improves upon that fix: by per-boot randomizing the > constant portion of the randomized range. I have this one on the TODO list for today, I'll take care of those formulations when applying. > Btw., does anyone know how relevant the performance fix is these days? > A simpler improvement would be to remove the workaround altogether and > recover proper randomization of bits 12,13,14. Nothing has changed with that respect in F15h, i.e. Bulldozer uarch. I think we still need this workaround in place. -- Regards/Gruss, Boris. ECO tip #101: Trim your mails when you reply. --