From patchwork Tue Nov 7 10:29:49 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Russell King (Oracle)" X-Patchwork-Id: 13448360 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 35F8CC4332F for ; Tue, 7 Nov 2023 10:30:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233973AbjKGKaY (ORCPT ); Tue, 7 Nov 2023 05:30:24 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45828 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233940AbjKGKaR (ORCPT ); Tue, 7 Nov 2023 05:30:17 -0500 Received: from pandora.armlinux.org.uk (pandora.armlinux.org.uk [IPv6:2001:4d48:ad52:32c8:5054:ff:fe00:142]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3B55010DC; Tue, 7 Nov 2023 02:30:12 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=armlinux.org.uk; s=pandora-2019; h=Date:Sender:Message-Id:Content-Type: Content-Transfer-Encoding:MIME-Version:Subject:Cc:To:From:References: In-Reply-To:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help: List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=rpX32JELJVRxbBajbNmSR45zpZhhmbYGw/k55Nv6FvI=; b=XN47gDlFG8oQadHagMkhORXF23 NRjFhMOv+fOecI9DuYcspnJ2wjxtrLSw4kI7bc6Pzft54dDr9K/i4r6/Gb3KEDyFfKfWMGKLgGrYB OSevVF3x5B/KPXN/975w4BVriOHzRvLd6esz2xUFlZRQoIRMjLTlSsaeP/Kceq2ToGjYHJ6dEQsLx fQrD1VL6a3tObH1/Fg4nNXaFBxAZCLqI4T5fb3Bnlg3+oIueijd3Enrj9JH7iCFWC6RLcKnDFwV7U 8rtN7+DW9WSr+UgP69IdSopcQdt+6g65W/qa/h/ObeMek38otWK872SHRRsHD1tTzmreGVN6/GjkW 7mlyujLw==; Received: from e0022681537dd.dyn.armlinux.org.uk ([fd8f:7570:feb6:1:222:68ff:fe15:37dd]:59044 helo=rmk-PC.armlinux.org.uk) by pandora.armlinux.org.uk with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.96) (envelope-from ) id 1r0JLB-0000Er-05; Tue, 07 Nov 2023 10:29:49 +0000 Received: from rmk by rmk-PC.armlinux.org.uk with local (Exim 4.94.2) (envelope-from ) id 1r0JLB-00CTwy-7y; Tue, 07 Nov 2023 10:29:49 +0000 In-Reply-To: References: From: Russell King (Oracle) To: linux-pm@vger.kernel.org, loongarch@lists.linux.dev, linux-acpi@vger.kernel.org, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-riscv@lists.infradead.org, kvmarm@lists.linux.dev, x86@kernel.org, linux-csky@vger.kernel.org, linux-doc@vger.kernel.org, linux-ia64@vger.kernel.org, linux-parisc@vger.kernel.org Cc: Salil Mehta , Jean-Philippe Brucker , jianyong.wu@arm.com, justin.he@arm.com, James Morse , Greg Kroah-Hartman , "Rafael J. Wysocki" , Paul Walmsley , Palmer Dabbelt , Albert Ou , Guo Ren Subject: [PATCH RFC 06/22] drivers: base: Use present CPUs in GENERIC_CPU_DEVICES MIME-Version: 1.0 Content-Disposition: inline Message-Id: Sender: Russell King Date: Tue, 07 Nov 2023 10:29:49 +0000 Precedence: bulk List-ID: X-Mailing-List: linux-parisc@vger.kernel.org From: James Morse Three of the five ACPI architectures create sysfs entries using register_cpu() for present CPUs, whereas arm64, riscv and all GENERIC_CPU_DEVICES do this for possible CPUs. Registering a CPU is what causes them to show up in sysfs. It makes very little sense to register all possible CPUs. Registering a CPU is what triggers the udev notifications allowing user-space to react to newly added CPUs. To allow all five ACPI architectures to use GENERIC_CPU_DEVICES, change it to use for_each_present_cpu(). Making the ACPI architectures use GENERIC_CPU_DEVICES is a pre-requisite step to centralise their cpu_register() logic, before moving it into the ACPI processor driver. When ACPI is disabled this work would be done by cpu_dev_register_generic(). Of the ACPI architectures that register possible CPUs, arm64 and riscv do not support making possible CPUs present as they use the weak 'always fails' version of arch_register_cpu(). Only two of the eight architectures that use GENERIC_CPU_DEVICES have a distinction between present and possible CPUs. The following architectures use GENERIC_CPU_DEVICES but are not SMP, so possible == present: * m68k * microblaze * nios2 The following architectures use GENERIC_CPU_DEVICES and consider possible == present: * csky: setup_smp() * processor_probe() sets possible for all CPUs and present for all CPUs except the boot cpu, which will have been done by init/main.c::start_kernel(). um appears to be a subarchitecture of x86. The remaining architecture using GENERIC_CPU_DEVICES are: * openrisc and hexagon: where smp_init_cpus() makes all CPUs < NR_CPUS possible, whereas smp_prepare_cpus() only makes CPUs < setup_max_cpus present. After this change, openrisc and hexagon systems that use the max_cpus command line argument would not see the other CPUs present in sysfs. This should not be a problem as these CPUs can't bre brought online as _cpu_up() checks cpu_present(). After this change, only CPUs which are present appear in sysfs. Signed-off-by: James Morse Reviewed-by: Jonathan Cameron Signed-off-by: Russell King (Oracle) Reviewed-by: Gavin Shan --- drivers/base/cpu.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c index 9ea22e165acd..34b48f660b6b 100644 --- a/drivers/base/cpu.c +++ b/drivers/base/cpu.c @@ -533,7 +533,7 @@ static void __init cpu_dev_register_generic(void) #ifdef CONFIG_GENERIC_CPU_DEVICES int i; - for_each_possible_cpu(i) { + for_each_present_cpu(i) { if (register_cpu(&per_cpu(cpu_devices, i), i)) panic("Failed to register CPU device"); }