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=-5.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,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 99C6AC433DB for ; Tue, 9 Feb 2021 14:51:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 55C9A64E5A for ; Tue, 9 Feb 2021 14:51:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232280AbhBIOvI (ORCPT ); Tue, 9 Feb 2021 09:51:08 -0500 Received: from foss.arm.com ([217.140.110.172]:52806 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232262AbhBIOu5 (ORCPT ); Tue, 9 Feb 2021 09:50:57 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id B9B54101E; Tue, 9 Feb 2021 06:50:11 -0800 (PST) Received: from [10.37.8.18] (unknown [10.37.8.18]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id C0F223F73D; Tue, 9 Feb 2021 06:50:09 -0800 (PST) Subject: Re: [PATCH v12 6/7] arm64: mte: Save/Restore TFSR_EL1 during suspend To: Lorenzo Pieralisi , Catalin Marinas Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, Andrew Morton , Will Deacon , Dmitry Vyukov , Andrey Ryabinin , Alexander Potapenko , Marco Elver , Evgenii Stepanov , Branislav Rankov , Andrey Konovalov References: <20210208165617.9977-1-vincenzo.frascino@arm.com> <20210208165617.9977-7-vincenzo.frascino@arm.com> <20210209115533.GE1435@arm.com> <20210209143328.GA27791@e121166-lin.cambridge.arm.com> From: Vincenzo Frascino Message-ID: <2a551330-111b-4cb4-51d1-190f2c6d8493@arm.com> Date: Tue, 9 Feb 2021 14:54:13 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20210209143328.GA27791@e121166-lin.cambridge.arm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2/9/21 2:33 PM, Lorenzo Pieralisi wrote: >> Do we need a similar fix for TFSRE0_EL1? We get away with this if >> suspend is only entered on the idle (kernel) thread but I recall we >> could also enter suspend on behalf of a user process (I may be wrong >> though). > Yes, when we suspend the machine to RAM, we execute suspend on behalf > on a userspace process (but that's only running on 1 cpu, the others > are hotplugged out). > > IIUC (and that's an if) TFSRE0_EL1 is checked on kernel entry so I don't > think there is a need to save/restore it (just reset it on suspend > exit). > > TFSR_EL1, I don't see a point in saving/restoring it (it is a bit > per-CPU AFAICS) either, IMO we should "check" it on suspend (if it is > possible in that context) and reset it on resume. > > I don't think though you can "check" with IRQs disabled so I suspect > that TFSR_EL1 has to be saved/restored (which means that there is a > black out period where we run kernel code without being able to detect > faults but there is no solution to that other than delaying saving the > value to just before calling into PSCI). Likewise on resume from low > power. > Ok, based on what you are saying it seems that the most viable solution here is to save and restore TFSR_EL1. I will update my code accordingly. > Thanks, > Lorenzo > -- Regards, Vincenzo