From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx121.postini.com [74.125.245.121]) by kanga.kvack.org (Postfix) with SMTP id 613F36B0072 for ; Fri, 26 Oct 2012 23:46:44 -0400 (EDT) Message-ID: <508B59B0.5010503@redhat.com> Date: Fri, 26 Oct 2012 23:49:04 -0400 From: Rik van Riel MIME-Version: 1.0 Subject: Re: [PATCH 2/3] x86,mm: drop TLB flush from ptep_set_access_flags References: <20121025121617.617683848@chello.nl> <20121025124832.840241082@chello.nl> <5089F5B5.1050206@redhat.com> <508A0A0D.4090001@redhat.com> <508A8D31.9000106@redhat.com> <20121026132601.GC9886@gmail.com> <20121026144502.6e94643e@dull> <20121026221254.7d32c8bf@pyramind.ukuu.org.uk> In-Reply-To: <20121026221254.7d32c8bf@pyramind.ukuu.org.uk> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Alan Cox Cc: Ingo Molnar , Andi Kleen , Michel Lespinasse , Linus Torvalds , Peter Zijlstra , Andrea Arcangeli , Mel Gorman , Johannes Weiner , Thomas Gleixner , Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org On 10/26/2012 05:12 PM, Alan Cox wrote: > On Fri, 26 Oct 2012 14:45:02 -0400 > Rik van Riel wrote: > >> Intel has an architectural guarantee that the TLB entry causing >> a page fault gets invalidated automatically. This means >> we should be able to drop the local TLB invalidation. >> >> Because of the way other areas of the page fault code work, >> chances are good that all x86 CPUs do this. However, if >> someone somewhere has an x86 CPU that does not invalidate >> the TLB entry causing a page fault, this one-liner should >> be easy to revert. > > This does not strike me as a good standard of validation for such a change > > At the very least we should have an ACK from AMD and from VIA, and > preferably ping RDC and some of the other embedded folks. Given an AMD > and VIA ACK I'd be fine. I doubt anyone knows any more what Cyrix CPUs > did or cared about and I imagine H Peter or Linus can answer for > Transmeta ;-) Fair enough. If it turns out any of those CPUs need an explicit flush, then we can also adjust flush_tlb_fix_spurious_fault to actually do a local flush on x86 (or at least on those CPUs). -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org