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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4220BC4167B for ; Tue, 28 Nov 2023 14:46:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1346321AbjK1OqQ (ORCPT ); Tue, 28 Nov 2023 09:46:16 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49108 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1345841AbjK1OqN (ORCPT ); Tue, 28 Nov 2023 09:46:13 -0500 Received: from frasgout.his.huawei.com (frasgout.his.huawei.com [185.176.79.56]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C5A0C8E; Tue, 28 Nov 2023 06:46:19 -0800 (PST) Received: from mail.maildlp.com (unknown [172.18.186.216]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4Sfld50B5Bz6GD2C; Tue, 28 Nov 2023 22:46:01 +0800 (CST) Received: from lhrpeml500005.china.huawei.com (unknown [7.191.163.240]) by mail.maildlp.com (Postfix) with ESMTPS id EDB31140CB9; Tue, 28 Nov 2023 22:46:17 +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, 28 Nov 2023 14:46:17 +0000 Date: Tue, 28 Nov 2023 14:46:16 +0000 From: Jonathan Cameron To: Russell King CC: , , , , , , , , , , , , , Salil Mehta , Jean-Philippe Brucker , , , James Morse , Huacai Chen , WANG Xuerui , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , "Rafael J. Wysocki" , Len Brown , Paul Walmsley , Palmer Dabbelt , Albert Ou Subject: Re: [PATCH RFC 05/22] ACPI: Move ACPI_HOTPLUG_CPU to be disabled on arm64 and riscv Message-ID: <20231128144616.00006ed0@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 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.202.227.76] X-ClientProxiedBy: lhrpeml500006.china.huawei.com (7.191.161.198) To lhrpeml500005.china.huawei.com (7.191.163.240) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 07 Nov 2023 10:29:44 +0000 Russell King wrote: > From: James Morse > > Neither arm64 nor riscv support physical hotadd of CPUs that were not > present at boot. For arm64 much of the platform description is in static > tables which do not have update methods. arm64 does support HOTPLUG_CPU, > which is backed by a firmware interface to turn CPUs on and off. > > acpi_processor_hotadd_init() and acpi_processor_remove() are for adding > and removing CPUs that were not present at boot. arm64 systems that do this > are not supported as there is currently insufficient information in the > platform description. (e.g. did the GICR get removed too?) > > arm64 currently relies on the MADT enabled flag check in map_gicc_mpidr() > to prevent CPUs that were not described as present at boot from being > added to the system. Similarly, riscv relies on the same check in > map_rintc_hartid(). Both architectures also rely on the weak 'always fails' > definitions of acpi_map_cpu() and arch_register_cpu(). > > Subsequent changes will redefine ACPI_HOTPLUG_CPU as making possible > CPUs present. Neither arm64 nor riscv support this. > > Disable ACPI_HOTPLUG_CPU for arm64 and riscv by removing 'default y' and > selecting it on the other three ACPI architectures. This allows the weak > definitions of some symbols to be removed. > > Signed-off-by: James Morse > Signed-off-by: Russell King (Oracle) Reviewed-by: Jonathan Cameron