Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751946Ab2KQPZa (ORCPT ); Sat, 17 Nov 2012 10:25:30 -0500 Received: from mx1.redhat.com ([209.132.183.28]:2562 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751766Ab2KQPZ3 (ORCPT ); Sat, 17 Nov 2012 10:25:29 -0500 Message-ID: <50A7AC33.5060308@redhat.com> Date: Sat, 17 Nov 2012 10:24:35 -0500 From: Rik van Riel User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:15.0) Gecko/20120827 Thunderbird/15.0 MIME-Version: 1.0 To: Linus Torvalds CC: Borislav Petkov , Alan Cox , Ingo Molnar , Andi Kleen , Michel Lespinasse , Peter Zijlstra , Andrea Arcangeli , Mel Gorman , Johannes Weiner , Thomas Gleixner , Andrew Morton , Linux Kernel Mailing List , linux-mm , Florian Fainelli , Borislav Petkov Subject: Re: [PATCH 2/3] x86,mm: drop TLB flush from ptep_set_access_flags References: <508A8D31.9000106@redhat.com> <20121026132601.GC9886@gmail.com> <20121026144502.6e94643e@dull> <20121026221254.7d32c8bf@pyramind.ukuu.org.uk> <508BE459.2080406@redhat.com> <20121029165705.GA4693@x1.osrc.amd.com> <20121117145015.GF16441@x1.osrc.amd.com> In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1306 Lines: 30 On 11/17/2012 09:56 AM, Linus Torvalds wrote: > On Sat, Nov 17, 2012 at 6:50 AM, Borislav Petkov wrote: >> I don't know, however, whether it would be prudent to have some sort of >> a cheap assertion in the code (cheaper than INVLPG %ADDR, although on >> older cpus we do MOV CR3) just in case. This should be enabled only with >> DEBUG_VM on, of course... > > I wonder how we could actually test for it. We'd have to have some > per-cpu page-fault address check (along with a generation count on the > mm or similar). I doubt we'd figure out anything that works reliably > and efficiently and would actually show any problems Would it be enough to simply print out a warning if we fault on the same address twice (or three times) in a row, and then flush the local TLB? I realize this would not just trigger on CPUs that fail to invalidate TLB entries that cause faults, but also on kernel paths that cause a page fault to be re-taken... ... but then again, don't we want to find those paths and fix them, anyway? :) -- All rights reversed -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/