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 X-Spam-Level: X-Spam-Status: No, score=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6150CC433B4 for ; Thu, 20 May 2021 13:03:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3E287610A8 for ; Thu, 20 May 2021 13:03:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243137AbhETNE6 (ORCPT ); Thu, 20 May 2021 09:04:58 -0400 Received: from mail.kernel.org ([198.145.29.99]:36648 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239964AbhETNDw (ORCPT ); Thu, 20 May 2021 09:03:52 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 686BB61184; Thu, 20 May 2021 13:02:27 +0000 (UTC) Date: Thu, 20 May 2021 14:02:25 +0100 From: Catalin Marinas To: Steven Price Cc: Marc Zyngier , Will Deacon , James Morse , Julien Thierry , Suzuki K Poulose , kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Dave Martin , Mark Rutland , Thomas Gleixner , qemu-devel@nongnu.org, Juan Quintela , "Dr. David Alan Gilbert" , Richard Henderson , Peter Maydell , Haibo Xu , Andrew Jones Subject: Re: [PATCH v12 3/8] arm64: mte: Sync tags for pages where PTE is untagged Message-ID: <20210520130224.GE12251@arm.com> References: <20210517123239.8025-1-steven.price@arm.com> <20210517123239.8025-4-steven.price@arm.com> <20210519180610.GE21619@arm.com> <3bac3a47-9f96-c7bf-e401-fdef60dcc9d8@arm.com> <20210520122550.GD12251@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210520122550.GD12251@arm.com> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, May 20, 2021 at 01:25:50PM +0100, Catalin Marinas wrote: > On Thu, May 20, 2021 at 12:55:21PM +0100, Steven Price wrote: > > The problem I hit is one of include dependencies: > > > > is_swap_pte() is defined (as a static inline) in > > include/linux/swapops.h. However the definition depends on > > pte_none()/pte_present() which are defined in pgtable.h - so there's a > > circular dependency. > > > > Open coding is_swap_pte() in set_pte_at() works, but it's a bit ugly. > > Any ideas on how to improve on the below? > > > > if (system_supports_mte() && pte_present(pte) && > > pte_access_permitted(pte, false) && !pte_special(pte)) { > > pte_t old_pte = READ_ONCE(*ptep); > > /* > > * We only need to synchronise if the new PTE has tags enabled > > * or if swapping in (in which case another mapping may have > > * set tags in the past even if this PTE isn't tagged). > > * (!pte_none() && !pte_present()) is an open coded version of > > * is_swap_pte() > > */ > > if (pte_tagged(pte) || (!pte_none(pte) && !pte_present(pte))) > > mte_sync_tags(old_pte, pte); > > } > > That's why I avoided testing my suggestion ;). I think we should just > add !pte_none() in there with a comment that it may be a swap pte and > use the is_swap_pte() again on the mte_sync_tags() path. We already have > the pte_present() check. Correction - pte_present() checks the new pte only, we need another for the old pte. So it looks like we'll open-code is_swap_pte(). -- Catalin