From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2DA2DC3526C for ; Mon, 7 Feb 2022 17:49:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1348667AbiBGRqf (ORCPT ); Mon, 7 Feb 2022 12:46:35 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57316 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1346053AbiBGRjy (ORCPT ); Mon, 7 Feb 2022 12:39:54 -0500 Received: from server.lespinasse.org (server.lespinasse.org [IPv6:2001:470:82ab::100:0]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BA100C0401D5 for ; Mon, 7 Feb 2022 09:39:53 -0800 (PST) DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=lespinasse.org; i=@lespinasse.org; q=dns/txt; s=srv-54-ed; t=1644255593; h=date : from : to : cc : subject : message-id : references : mime-version : content-type : in-reply-to : from; bh=tmDPD28soEhWKnT4DxmAlJVsPBF7OE1oQKQpzgysMBQ=; b=JWSanQhlWOlcCshcpo0ZLiIFik09w09xx0LOoJpxqM/35WhVvLXux5ETCN/tYTwOPZOmH Sz+OEp1YBGocQSbDw== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=lespinasse.org; i=@lespinasse.org; q=dns/txt; s=srv-54-rsa; t=1644255593; h=date : from : to : cc : subject : message-id : references : mime-version : content-type : in-reply-to : from; bh=tmDPD28soEhWKnT4DxmAlJVsPBF7OE1oQKQpzgysMBQ=; b=azqVTrJC2t9aHb73Mc7K5JF3T+Ei7qWcPfKtwXIkOLCBlUKpwcUefS5+HLMknaaJNR7tX 09k3gRggYZbk6RtWhH4dLIy/iIqvJ1mtxDJYhJA0vrlg+DDxHMbSwE4oEQZGwu48sFU/O/H HKLYjp2GJkyyYBkNbcIspA33ASwU7aZ2YF7ilD7i05GCftosl6T4Gab299dyBrBjS89/M7Y ULbWqTUcGqS9ybPDUrMfFx/BhdL2OWcKqfx/Ru7gz73vplukNMscipuB9HYboK/J6I3Mkbm 8bMdrDEZgMi7U0O5ugo7YkWZPidtJ9w/Vt627tq3RR1wLfmtdri8qwpugHSw== Received: by server.lespinasse.org (Postfix, from userid 1000) id 8910E160B2F; Mon, 7 Feb 2022 09:39:53 -0800 (PST) Date: Mon, 7 Feb 2022 09:39:53 -0800 From: Michel Lespinasse To: Matthew Wilcox Cc: Andrew Morton , Michel Lespinasse , Linux-MM , linux-kernel@vger.kernel.org, kernel-team@fb.com, Laurent Dufour , Jerome Glisse , Peter Zijlstra , Michal Hocko , Vlastimil Babka , Davidlohr Bueso , Liam Howlett , Rik van Riel , Paul McKenney , Song Liu , Suren Baghdasaryan , Minchan Kim , Joel Fernandes , David Rientjes , Axel Rasmussen , Andy Lutomirski , Sebastian Andrzej Siewior Subject: Re: [PATCH v2 00/35] Speculative page faults Message-ID: <20220207173953.GD12302@lespinasse.org> References: <20220128131006.67712-1-michel@lespinasse.org> <20220131171434.89870a8f1ae294912e7ff19e@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Feb 01, 2022 at 02:20:39AM +0000, Matthew Wilcox wrote: > On Mon, Jan 31, 2022 at 05:14:34PM -0800, Andrew Morton wrote: > > On Fri, 28 Jan 2022 05:09:31 -0800 Michel Lespinasse wrote: > > > The next step is to walk down the existing page table tree to find the > > > current pte entry. This is done with interrupts disabled to avoid > > > races with munmap(). > > > > Sebastian, could you please comment on this from the CONFIG_PREEMPT_RT > > point of view? > > I am not a fan of this approach. For other reasons, I think we want to > switch to RCU-freed page tables, and then we can walk the page tables > with the RCU lock held. Some architectures already RCU-free the page > tables, so I think it's just a matter of converting the rest. Note - I have no problem with switching to RCU-freed page tables everywhere when and if we end up needing to. I just don't see that this need comes from the SPF patchset, so I don't think this should be introduced as an artificial dependency. -- Michel "walken" Lespinasse