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 51853EEAA4F for ; Thu, 14 Sep 2023 14:57:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id: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=hoNlaEzTJZ2ktb0i1TMvTqClj/d7ojH5TdH83nmi810=; b=NX7NtzKMnUryBD WHjbrK5C33seAy3exnRaVxCt42TrYRwDzxCefLGIvw1DmgMR0U+afMDXtgTAvAZFPArHW1jdIQSGs guIXpPjsxre3mDfkKjt5J4EdOqDXYzTjnZu7I4nUByKCRLbUi9o/drO2S7rUz44EBTkP9FWAKLOlk dPod3uF9CDkan5ZXVieq4tqRKf0KpYudchQNKd/GZTHdsXhy1IJTx3gu0zZCKwj3fvz4kuruwZUje oZHcRegIEJfL5UDptqeMOxt1wrnjk8fCaWLY27YdaXeyKytABqh3E2MkGASa3vgJjFBOfAV0qtyK1 l29ujCgbqwd/U8OHIVGA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1qgnln-008hi1-1J; Thu, 14 Sep 2023 14:56:39 +0000 Received: from frasgout.his.huawei.com ([185.176.79.56]) by bombadil.infradead.org with esmtps (Exim 4.96 #2 (Red Hat Linux)) id 1qgnlj-008hhE-2c; Thu, 14 Sep 2023 14:56:37 +0000 Received: from lhrpeml500005.china.huawei.com (unknown [172.18.147.201]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4RmgP90gY1z67Q1Y; Thu, 14 Sep 2023 22:55:57 +0800 (CST) Received: from localhost (10.202.227.76) by lhrpeml500005.china.huawei.com (7.191.163.240) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.31; Thu, 14 Sep 2023 15:56:33 +0100 Date: Thu, 14 Sep 2023 15:56:32 +0100 From: Jonathan Cameron To: "Russell King (Oracle)" CC: James Morse , , , , , , , , , , Salil Mehta , Jean-Philippe Brucker , , Subject: Re: [RFC PATCH v2 06/35] arm64: setup: Switch over to GENERIC_CPU_DEVICES using arch_register_cpu() Message-ID: <20230914155632.00003ca9@Huawei.com> In-Reply-To: References: <20230913163823.7880-1-james.morse@arm.com> <20230913163823.7880-7-james.morse@arm.com> <20230914122715.000076be@Huawei.com> Organization: Huawei Technologies Research and Development (UK) Ltd. X-Mailer: Claws Mail 4.1.0 (GTK 3.24.33; x86_64-w64-mingw32) MIME-Version: 1.0 X-Originating-IP: [10.202.227.76] X-ClientProxiedBy: lhrpeml100005.china.huawei.com (7.191.160.25) To lhrpeml500005.china.huawei.com (7.191.163.240) X-CFilter-Loop: Reflected X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230914_075636_128828_F965B036 X-CRM114-Status: GOOD ( 25.79 ) 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: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, 14 Sep 2023 15:07:22 +0100 "Russell King (Oracle)" wrote: > On Thu, Sep 14, 2023 at 12:27:15PM +0100, Jonathan Cameron wrote: > > On Wed, 13 Sep 2023 16:37:54 +0000 > > James Morse wrote: > > > > > To allow ACPI's _STA value to hide CPUs that are present, but not > > > available to online right now due to VMM or firmware policy, the > > > register_cpu() call needs to be made by the ACPI machinery when ACPI > > > is in use. This allows it to hide CPUs that are unavailable from sysfs. > > > > > > Switching to GENERIC_CPU_DEVICES is an intermediate step to allow all > > > five ACPI architectures to be modified at once. > > > > > > Switch over to GENERIC_CPU_DEVICES, and provide an arch_register_cpu() > > > that populates the hotpluggable flag. arch_register_cpu() is also the > > > interface the ACPI machinery expects. > > > > > > The struct cpu in struct cpuinfo_arm64 is never used directly, remove > > > it to use the one GENERIC_CPU_DEVICES provides. > > > > > > This changes the CPUs visible in sysfs from possible to present, but > > > on arm64 smp_prepare_cpus() ensures these are the same. > > > > > > Signed-off-by: James Morse > > > > After this the earlier question about ordering of cpu_dev_init() > > and node_dev_init() is relevant. > > > > Why won't node_dev_init() call > > get_cpu_devce() which queries per_cpu(cpu_sys_devices) > > and get NULL as we haven't yet filled that in? > > > > Or does it do so but that doesn't matter as well create the > > relevant links later? > > node_dev_init() will walk through the nodes calling register_one_node() > on each. This will trickle down to __register_one_node() which walks > all present CPUs, calling register_cpu_under_node() on each. > > register_cpu_under_node() will call get_cpu_device(cpu) for each and > will return NULL until the CPU is registered using register_cpu(), > which will now happen _after_ node_dev_init(). > > So, at this point, CPUs won't get registered, and initially one might > think that's a problem. > > However, register_cpu() will itself call register_cpu_under_node(), > where get_cpu_device() will return the now populated entry, and the > sysfs links will be created. > > So, I think what you've spotted is a potential chunk of code that > isn't necessary when using GENERIC_CPU_DEVICES after this change! > Makes sense thanks. I was just being too lazy to check and bouncing it back at James! *looks guilty* Jonathan _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel