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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id E558ECAC587 for ; Thu, 11 Sep 2025 15:07:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:MIME-Version:References:In-Reply-To:Message-ID:Subject:CC:To: From:Date:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=ykN1fhcN+BgDhyvUANmiPUFHkQX51aOUk9s/ymYlhpQ=; b=FY3oho/xYHhVjqb53v75sFXDGk fsYZzgX1Qd5qWFcS4K0WkXxfdnrwQyFqFqhrEJVN0R76iZ3J2hb08cQko8C5t3NWiRacjH+q9ZhEi YxoVscQV0w+Q6LhbwJxHlbOxZlDxFRSSRXtkQVldy4JTE+sDkyKuJK8+N2mmq4a9H1Vj7iMqiE2th 6DvYVe5Xp16Y/Y9Qynkxy2mdwVbjzGh6l0rhv03qDgxSDVq4v1bqnay2lDc7oiZrr2nk478BvEtcU AMP43W3P5q+Oft6paRbi+THT09GZUKMZHnmb5qQ3drQcrkuKZpqqImneG6iFJwdYL4Iqa7qviLIi4 ZlLBzKqw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1uwitq-00000003lgD-3hYR; Thu, 11 Sep 2025 15:07:50 +0000 Received: from frasgout.his.huawei.com ([185.176.79.56]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1uwito-00000003leG-1vCl for linux-arm-kernel@lists.infradead.org; Thu, 11 Sep 2025 15:07:49 +0000 Received: from mail.maildlp.com (unknown [172.18.186.231]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4cN19D68wwz6GD8p; Thu, 11 Sep 2025 23:06:24 +0800 (CST) Received: from frapeml500008.china.huawei.com (unknown [7.182.85.71]) by mail.maildlp.com (Postfix) with ESMTPS id 6F8BD1400D9; Thu, 11 Sep 2025 23:07:40 +0800 (CST) Received: from localhost (10.203.177.15) by frapeml500008.china.huawei.com (7.182.85.71) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.1.2507.39; Thu, 11 Sep 2025 17:07:39 +0200 Date: Thu, 11 Sep 2025 16:07:37 +0100 From: Jonathan Cameron To: James Morse CC: , , , D Scott Phillips OS , , , , , , Jamie Iles , Xin Hao , , , , David Hildenbrand , Dave Martin , Koba Ko , Shanker Donthineni , , , Rob Herring , Rohit Mathew , "Rafael Wysocki" , Len Brown , Lorenzo Pieralisi , Hanjun Guo , Sudeep Holla , Catalin Marinas , "Will Deacon" , Greg Kroah-Hartman , Danilo Krummrich , Lecopzer Chen Subject: Re: [PATCH v2 10/29] arm_mpam: Add cpuhp callbacks to probe MSC hardware Message-ID: <20250911160737.0000492f@huawei.com> In-Reply-To: <20250910204309.20751-11-james.morse@arm.com> References: <20250910204309.20751-1-james.morse@arm.com> <20250910204309.20751-11-james.morse@arm.com> X-Mailer: Claws Mail 4.3.0 (GTK 3.24.42; x86_64-w64-mingw32) MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.203.177.15] X-ClientProxiedBy: lhrpeml500005.china.huawei.com (7.191.163.240) To frapeml500008.china.huawei.com (7.182.85.71) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250911_080748_783216_07D0683E X-CRM114-Status: GOOD ( 23.31 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, 10 Sep 2025 20:42:50 +0000 James Morse wrote: > Because an MSC can only by accessed from the CPUs in its cpu-affinity > set we need to be running on one of those CPUs to probe the MSC > hardware. > > Do this work in the cpuhp callback. Probing the hardware will only > happen before MPAM is enabled, walk all the MSCs and probe those we can > reach that haven't already been probed as each CPU's online call is made. > > This adds the low-level MSC register accessors. > > Once all MSCs reported by the firmware have been probed from a CPU in > their respective cpu-affinity set, the probe-time cpuhp callbacks are > replaced. The replacement callbacks will ultimately need to handle > save/restore of the runtime MSC state across power transitions, but for > now there is nothing to do in them: so do nothing. > > The architecture's context switch code will be enabled by a static-key, > this can be set by mpam_enable(), but must be done from process context, > not a cpuhp callback because both take the cpuhp lock. > Whenever a new MSC has been probed, the mpam_enable() work is scheduled > to test if all the MSCs have been probed. If probing fails, mpam_disable() > is scheduled to unregister the cpuhp callbacks and free memory. > > CC: Lecopzer Chen > Signed-off-by: James Morse Trivial suggestion inline. Either way Reviewed-by: Jonathan Cameron > + > +/* Before mpam is enabled, try to probe new MSC */ > +static int mpam_discovery_cpu_online(unsigned int cpu) > +{ > + int err = 0; > + struct mpam_msc *msc; > + bool new_device_probed = false; > + > + guard(srcu)(&mpam_srcu); > + list_for_each_entry_srcu(msc, &mpam_all_msc, all_msc_list, > + srcu_read_lock_held(&mpam_srcu)) { > + if (!cpumask_test_cpu(cpu, &msc->accessibility)) > + continue; > + > + mutex_lock(&msc->probe_lock); > + if (!msc->probed) > + err = mpam_msc_hw_probe(msc); > + mutex_unlock(&msc->probe_lock); > + > + if (!err) > + new_device_probed = true; > + else > + break; Unless this going to get more complex why not if (err) break; new_device_probed = true; > + } > + > + if (new_device_probed && !err) > + schedule_work(&mpam_enable_work); > + if (err) { > + mpam_disable_reason = "error during probing"; > + schedule_work(&mpam_broken_work); > + } > + > + return err; > +} > +static void mpam_enable_once(void) > +{ > + mpam_register_cpuhp_callbacks(mpam_cpu_online, mpam_cpu_offline); > + > + pr_info("MPAM enabled\n"); Feels too noisy given it should be easy enough to tell. pr_dbg() perhaps. > +}