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=-11.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable 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 BCBDCC433DF for ; Tue, 25 Aug 2020 11:32:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A31122075F for ; Tue, 25 Aug 2020 11:32:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730039AbgHYLbi (ORCPT ); Tue, 25 Aug 2020 07:31:38 -0400 Received: from foss.arm.com ([217.140.110.172]:56696 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730037AbgHYLbe (ORCPT ); Tue, 25 Aug 2020 07:31:34 -0400 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 9BE1830E; Tue, 25 Aug 2020 04:31:33 -0700 (PDT) Received: from localhost (unknown [10.1.199.49]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 3CF913F66B; Tue, 25 Aug 2020 04:31:33 -0700 (PDT) Date: Tue, 25 Aug 2020 12:31:31 +0100 From: Ionela Voinescu To: Viresh Kumar Cc: rjw@rjwysocki.net, dietmar.eggemann@arm.com, catalin.marinas@arm.com, sudeep.holla@arm.com, will@kernel.org, valentin.schneider@arm.com, linux-pm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 1/5] arch_topology: validate input frequencies to arch_set_freq_scale() Message-ID: <20200825113131.GB12506@arm.com> References: <20200824210252.27486-1-ionela.voinescu@arm.com> <20200824210252.27486-2-ionela.voinescu@arm.com> <20200825055618.ybght3enlpuwo3va@vireshk-i7> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200825055618.ybght3enlpuwo3va@vireshk-i7> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org On Tuesday 25 Aug 2020 at 11:26:18 (+0530), Viresh Kumar wrote: > On 24-08-20, 22:02, Ionela Voinescu wrote: > > The current frequency passed to arch_set_freq_scale() could end up > > being 0, signaling an error in setting a new frequency. Also, if the > > maximum frequency in 0, this will result in a division by 0 error. > > > > Therefore, validate these input values before using them for the > > setting of the frequency scale factor. > > > > Signed-off-by: Ionela Voinescu > > Cc: Sudeep Holla > > Cc: Rafael J. Wysocki > > --- > > drivers/base/arch_topology.c | 3 +++ > > 1 file changed, 3 insertions(+) > > > > diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c > > index 75f72d684294..1aca82fcceb8 100644 > > --- a/drivers/base/arch_topology.c > > +++ b/drivers/base/arch_topology.c > > @@ -33,6 +33,9 @@ void arch_set_freq_scale(struct cpumask *cpus, unsigned long cur_freq, > > unsigned long scale; > > int i; > > > > + if (!cur_freq || !max_freq) > > We should probably use unlikely() here. > > Rafael: Shouldn't this have a WARN_ON_ONCE() as well ? > I'll add the unlikely() as it's definitely useful. I'm somewhat on the fence about WARN_ON_ONCE() here. Wouldn't it work better in cpufreq_driver_fast_switch()? It would cover scenarios where the default arch_set_freq_scale() is used and flag potential hardware issues with setting frequency that are currently just ignored both here and in sugov_fast_switch(). Thanks, Ionela.