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 DC40BC47074 for ; Tue, 2 Jan 2024 14:53:57 +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=MWsO5VO7im/boKkB8WsZl9KtxxV48Q90fpqhhQMPWK4=; b=2hgQvh4twCQbAA 22NzV1WI1EjUm691w+ss4qV9r+COhDpfYYu8tOo6kDJ2Yr0v0zaxyXMIBww3ViUBFCtxoSq/sZaSz pVz14sHQICTwmIO2qTSdJGpHLx0GJj/aEbTPb47CfaQCj8o2jHb3MuSp9EWjFMOsbI7VYcmteLiJY wOuaeVTDBDQxgTeIgYerwUqGvPoMPr7HBGvSF534rxVhulbY+a+RwBvFTCcHyzcoaRhShXeUfqVQd EC/MOJ/ZWKgIX/bwWjXIy1HFhYJrh0qSI0H/vtl1mc7c7gxwST7ut0ZkjTIMTwg8PoXqVL4raSvwE SvrHumniQx96XrEkFanw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1rKg98-008IZT-0p; Tue, 02 Jan 2024 14:53:34 +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 1rKg94-008IX6-1m; Tue, 02 Jan 2024 14:53:32 +0000 Received: from mail.maildlp.com (unknown [172.18.186.216]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4T4G5q1Xwbz6K5pD; Tue, 2 Jan 2024 22:51:59 +0800 (CST) Received: from lhrpeml500005.china.huawei.com (unknown [7.191.163.240]) by mail.maildlp.com (Postfix) with ESMTPS id D4BBB1400DB; Tue, 2 Jan 2024 22:53:22 +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 15.1.2507.35; Tue, 2 Jan 2024 14:53:22 +0000 Date: Tue, 2 Jan 2024 14:53:20 +0000 From: Jonathan Cameron To: "Russell King (Oracle)" CC: , , , , , , , , , , , , , , Salil Mehta , Jean-Philippe Brucker , , , James Morse Subject: Re: [PATCH RFC v3 17/21] ACPI: add support to register CPUs based on the _STA enabled bit Message-ID: <20240102145320.000062f9@Huawei.com> In-Reply-To: References: 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: lhrpeml100002.china.huawei.com (7.191.160.241) To lhrpeml500005.china.huawei.com (7.191.163.240) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240102_065330_907024_DA539EAD X-CRM114-Status: GOOD ( 22.84 ) 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 Mon, 18 Dec 2023 13:03:32 +0000 "Russell King (Oracle)" wrote: > On Wed, Dec 13, 2023 at 12:50:38PM +0000, Russell King wrote: > > From: James Morse > > > > acpi_processor_get_info() registers all present CPUs. Registering a > > CPU is what creates the sysfs entries and triggers the udev > > notifications. > > > > arm64 virtual machines that support 'virtual cpu hotplug' use the > > enabled bit to indicate whether the CPU can be brought online, as > > the existing ACPI tables require all hardware to be described and > > present. > > > > If firmware describes a CPU as present, but disabled, skip the > > registration. Such CPUs are present, but can't be brought online for > > whatever reason. (e.g. firmware/hypervisor policy). > > > > Once firmware sets the enabled bit, the CPU can be registered and > > brought online by user-space. Online CPUs, or CPUs that are missing > > an _STA method must always be registered. > > ... > > > @@ -526,6 +552,9 @@ static void acpi_processor_post_eject(struct acpi_device *device) > > acpi_processor_make_not_present(device); > > return; > > } > > + > > + if (cpu_present(pr->id) && !(sta & ACPI_STA_DEVICE_ENABLED)) > > + arch_unregister_cpu(pr->id); > > This change isn't described in the commit log, but seems to be the cause > of the build error identified by the kernel build bot that is fixed > later in this series. I'm wondering whether this should be in a > different patch, maybe "ACPI: Check _STA present bit before making CPUs > not present" ? Would seem a bit odd to call arch_unregister_cpu() way before the code is added to call the matching arch_registers_cpu() Mind you this eject doesn't just apply to those CPUs that are registered later I think, but instead to all. So we run into the spec hole that there is no way to identify initially 'enabled' CPUs that might be disabled later. > > Or maybe my brain isn't working properly (due to being Covid positive.) > Any thoughts, Jonathan? I'll go with a resounding 'not sure' on where this change belongs. I blame my non existent start of the year hangover. Hope you have recovered! Jonathan _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel