From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754917Ab3K2VY5 (ORCPT ); Fri, 29 Nov 2013 16:24:57 -0500 Received: from terminus.zytor.com ([198.137.202.10]:53548 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752606Ab3K2VYy (ORCPT ); Fri, 29 Nov 2013 16:24:54 -0500 Message-ID: <529905F9.30703@zytor.com> Date: Fri, 29 Nov 2013 13:24:09 -0800 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.1.0 MIME-Version: 1.0 To: Oleg Nesterov CC: Andi Kleen , linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, x86@kernel.org, Andi Kleen , Ingo Molnar , Borislav Petkov Subject: Re: [PATCH] Add a text_poke syscall v2 References: <1385426236-14960-1-git-send-email-andi@firstfloor.org> <20131129183558.GA9803@redhat.com> <20131129195419.GB17656@two.firstfloor.org> <20131129200532.GA13561@redhat.com> <5298F66A.2010600@zytor.com> <20131129203550.GA14723@redhat.com> In-Reply-To: <20131129203550.GA14723@redhat.com> X-Enigmail-Version: 1.6 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/29/2013 12:35 PM, Oleg Nesterov wrote: > On 11/29, H. Peter Anvin wrote: >> >> On 11/29/2013 12:05 PM, Oleg Nesterov wrote: >>> >>> Can't we invalidate pte (so that any user will stuck in page fault), >>> update the page(s), restore the pte and drop the locks? >> >> That would require a global TLB shootdown > > Well, it is not really global, it is for mm_cpumask() and for good > reason? > > And is it really worse than on_each_cpu(do_sync_core) and the usage > of text_mutex? > Probably not, but one would have to consider the total amount of synchronization needed. >> (and wouldn't help >> shared-memory code segments, if we care about that at all.) > > Well, I think this should only support the private mappings. > Well, what do you do if someone tries this on a MAP_SHARED mapping? Error out? -hpa