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 37C0BEEAA53 for ; Thu, 14 Sep 2023 16:13:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236275AbjINQNu (ORCPT ); Thu, 14 Sep 2023 12:13:50 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45612 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232330AbjINQNt (ORCPT ); Thu, 14 Sep 2023 12:13:49 -0400 Received: from frasgout.his.huawei.com (frasgout.his.huawei.com [185.176.79.56]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7ECC21BE1; Thu, 14 Sep 2023 09:13:45 -0700 (PDT) Received: from lhrpeml500005.china.huawei.com (unknown [172.18.147.226]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4Rmj4r2vBYz6HJcg; Fri, 15 Sep 2023 00:11:56 +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 17:13:41 +0100 Date: Thu, 14 Sep 2023 17:13:41 +0100 From: Jonathan Cameron To: James Morse CC: , , , , , , , , , Salil Mehta , Russell King , Jean-Philippe Brucker , , Subject: Re: [RFC PATCH v2 32/35] ACPI: add support to register CPUs based on the _STA enabled bit Message-ID: <20230914171341.00006e51@Huawei.com> In-Reply-To: <20230913163823.7880-33-james.morse@arm.com> References: <20230913163823.7880-1-james.morse@arm.com> <20230913163823.7880-33-james.morse@arm.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 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) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-arch@vger.kernel.org On Wed, 13 Sep 2023 16:38:20 +0000 James Morse wrote: > 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. > > Signed-off-by: James Morse A small argument with myself inline. Feel free to ignore. Reviewed-by: Jonathan Cameron > --- > drivers/acpi/acpi_processor.c | 31 ++++++++++++++++++++++++++++++- > 1 file changed, 30 insertions(+), 1 deletion(-) > > diff --git a/drivers/acpi/acpi_processor.c b/drivers/acpi/acpi_processor.c > index b67616079751..b49859eab01a 100644 > --- a/drivers/acpi/acpi_processor.c > +++ b/drivers/acpi/acpi_processor.c > @@ -227,6 +227,32 @@ static int acpi_processor_make_present(struct acpi_processor *pr) > return ret; > } > > +static int acpi_processor_make_enabled(struct acpi_processor *pr) > +{ > + unsigned long long sta; > + acpi_status status; > + bool present, enabled; > + > + if (!acpi_has_method(pr->handle, "_STA")) > + return arch_register_cpu(pr->id); > + > + status = acpi_evaluate_integer(pr->handle, "_STA", NULL, &sta); > + if (ACPI_FAILURE(status)) > + return -ENODEV; > + > + present = sta & ACPI_STA_DEVICE_PRESENT; > + enabled = sta & ACPI_STA_DEVICE_ENABLED; > + > + if (cpu_online(pr->id) && (!present || !enabled)) { > + pr_err_once(FW_BUG "CPU %u is online, but described as not present or disabled!\n", pr->id); Why once? If this for some reason happened on multiple CPUs I think we'd want to know. > + add_taint(TAINT_FIRMWARE_WORKAROUND, LOCKDEP_STILL_OK); > + } else if (!present || !enabled) { > + return -ENODEV; > + } I guess you didn't do a nested if here to avoid even longer lines. Could flip things around though I don't like this much either as it makes the normal good path exit mid way down. if (present && enabled) return arch_register_cpu(pr->id); if (!cpu_online(pr->id)) return -ENODEV; pr_err... add_taint(... return arch_register_cpu(pr->id); Ah well. Some code just has to be less than pretty. > + > + return arch_register_cpu(pr->id); > +} > + > static int acpi_processor_get_info(struct acpi_device *device) > { > union acpi_object object = { 0 }; > @@ -318,7 +344,7 @@ static int acpi_processor_get_info(struct acpi_device *device) > */ > if (!invalid_logical_cpuid(pr->id) && cpu_present(pr->id) && > !get_cpu_device(pr->id)) { > - int ret = arch_register_cpu(pr->id); > + int ret = acpi_processor_make_enabled(pr); > > if (ret) > return ret; > @@ -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); > } > > #ifdef CONFIG_ARCH_MIGHT_HAVE_ACPI_PDC