Message ID | E1r0JLB-00CTwy-7y@rmk-PC.armlinux.org.uk |
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State | New |
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[2620:137:e000::3:7]) by mx.google.com with ESMTPS id j20-20020a170902f25400b001c610ae885bsi9802070plc.59.2023.11.07.02.32.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 07 Nov 2023 02:32:41 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:7 as permitted sender) client-ip=2620:137:e000::3:7; Authentication-Results: mx.google.com; dkim=fail (test mode) header.i=@armlinux.org.uk header.s=pandora-2019 header.b=XN47gDlF; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:7 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=armlinux.org.uk Received: from out1.vger.email (depot.vger.email [IPv6:2620:137:e000::3:0]) by snail.vger.email (Postfix) with ESMTP id CD2C780707E4; Tue, 7 Nov 2023 02:30:29 -0800 (PST) X-Virus-Status: Clean X-Virus-Scanned: clamav-milter 0.103.10 at snail.vger.email Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234027AbjKGKaZ (ORCPT <rfc822;lhua1029@gmail.com> + 32 others); Tue, 7 Nov 2023 05:30:25 -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 <rfc822;linux-kernel@vger.kernel.org>); 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 <rmk@armlinux.org.uk>) 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 <rmk@rmk-PC.armlinux.org.uk>) id 1r0JLB-00CTwy-7y; Tue, 07 Nov 2023 10:29:49 +0000 In-Reply-To: <ZUoRY33AAHMc5ThW@shell.armlinux.org.uk> References: <ZUoRY33AAHMc5ThW@shell.armlinux.org.uk> From: Russell King (Oracle) <rmk+kernel@armlinux.org.uk> 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 <salil.mehta@huawei.com>, Jean-Philippe Brucker <jean-philippe@linaro.org>, jianyong.wu@arm.com, justin.he@arm.com, James Morse <james.morse@arm.com>, Greg Kroah-Hartman <gregkh@linuxfoundation.org>, "Rafael J. Wysocki" <rafael@kernel.org>, Paul Walmsley <paul.walmsley@sifive.com>, Palmer Dabbelt <palmer@dabbelt.com>, Albert Ou <aou@eecs.berkeley.edu>, Guo Ren <guoren@kernel.org> Subject: [PATCH RFC 06/22] drivers: base: Use present CPUs in GENERIC_CPU_DEVICES MIME-Version: 1.0 Content-Disposition: inline Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset="utf-8" Message-Id: <E1r0JLB-00CTwy-7y@rmk-PC.armlinux.org.uk> Sender: Russell King <rmk@armlinux.org.uk> Date: Tue, 07 Nov 2023 10:29:49 +0000 X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,SPF_HELO_NONE,SPF_NONE, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: <linux-kernel.vger.kernel.org> X-Mailing-List: linux-kernel@vger.kernel.org X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (snail.vger.email [0.0.0.0]); Tue, 07 Nov 2023 02:30:29 -0800 (PST) X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1781900940599162017 X-GMAIL-MSGID: 1781900940599162017 |
Series |
Initial cleanups for vCPU hotplug
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Commit Message
Russell King (Oracle)
Nov. 7, 2023, 10:29 a.m. UTC
From: James Morse <james.morse@arm.com> 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 <james.morse@arm.com> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com> Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk> --- drivers/base/cpu.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
Comments
Hi Russell, On 11/7/23 18:29, Russell King (Oracle) wrote: > From: James Morse <james.morse@arm.com> > > 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(). What do you actually mean about when ACPI is disabled this work would be done by cpu_dev_register_generic()? Is the work means register the cpu? I'm not quite understand that, and how about when ACPI is enabled, which function do this work? > > 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 ^ nit: can't be > _cpu_up() checks cpu_present(). > > After this change, only CPUs which are present appear in sysfs. > > Signed-off-by: James Morse <james.morse@arm.com> > Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com> > Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk> Thanks, Shaoqin > --- > 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"); > }
On Thu, Nov 09, 2023 at 06:09:32PM +0800, Shaoqin Huang wrote: > Hi Russell, > > On 11/7/23 18:29, Russell King (Oracle) wrote: > > From: James Morse <james.morse@arm.com> > > > > 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(). > > What do you actually mean about when ACPI is disabled this work would be Firstly, please note that "you" is not appropriate here. This is James' commit message, not mine. > done by cpu_dev_register_generic()? Is the work means register the cpu? When ACPI is disabled _and_ CONFIG_GENERIC_CPU_DEVICES is enabled, then cpu_dev_register_generic() will call arch_register_cpu() for each present CPU after this commit, rather than for each _possible_ CPU (which is the actual code change here.) > I'm not quite understand that, and how about when ACPI is enabled, which > function do this work? This is what happens later in the series. "drivers: base: Allow parts of GENERIC_CPU_DEVICES to be overridden" adds a test for CONFIG_GENERIC_CPU_DEVICES, so this will only be used with architectures using GENERIC_CPU_DEVICES. Then in: "ACPI: processor: Register all CPUs from acpi_processor_get_info()" which is not part of this series, this adds a call to arch_register_cpu() in the ACPI code, and disables this path via a test for !acpi_disabled. Essentially, this path gets used to register the present CPUs when firmware (ACPI) isn't going to be registering the present CPUs. I've changed this to: "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 register_cpu() logic, before moving it into the ACPI processor driver. When we add support for register CPUs from ACPI in a later patch, we will avoid registering CPUs in this path." which I hope makes it clearer. > > 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 > ^ nit: can't be Thanks, I'll fix that.
On 11/9/23 18:29, Russell King (Oracle) wrote: > On Thu, Nov 09, 2023 at 06:09:32PM +0800, Shaoqin Huang wrote: >> Hi Russell, >> >> On 11/7/23 18:29, Russell King (Oracle) wrote: >>> From: James Morse <james.morse@arm.com> >>> >>> 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(). >> >> What do you actually mean about when ACPI is disabled this work would be > > Firstly, please note that "you" is not appropriate here. This is James' > commit message, not mine. > Oh, Sorry for that. >> done by cpu_dev_register_generic()? Is the work means register the cpu? > > When ACPI is disabled _and_ CONFIG_GENERIC_CPU_DEVICES is enabled, then > cpu_dev_register_generic() will call arch_register_cpu() for each present > CPU after this commit, rather than for each _possible_ CPU (which is the > actual code change here.) > >> I'm not quite understand that, and how about when ACPI is enabled, which >> function do this work? > > This is what happens later in the series. > > "drivers: base: Allow parts of GENERIC_CPU_DEVICES to be overridden" > adds a test for CONFIG_GENERIC_CPU_DEVICES, so this will only be used > with architectures using GENERIC_CPU_DEVICES. Then in: > > "ACPI: processor: Register all CPUs from acpi_processor_get_info()" > which is not part of this series, this adds a call to arch_register_cpu() > in the ACPI code, and disables this path via a test for !acpi_disabled. > > Essentially, this path gets used to register the present CPUs when > firmware (ACPI) isn't going to be registering the present CPUs. > > I've changed this to: > > "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 register_cpu() logic, before moving it into the > ACPI processor driver. When we add support for register CPUs from ACPI > in a later patch, we will avoid registering CPUs in this path." > > which I hope makes it clearer. > Thanks for your great explanation. Change commit message to this makes me understand well. Thanks, Shaoqin >>> 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 >> ^ nit: can't be > > Thanks, I'll fix that. >
On 11/7/23 20:29, Russell King (Oracle) wrote: > From: James Morse <james.morse@arm.com> > > 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 <james.morse@arm.com> > Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com> > Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk> > --- > drivers/base/cpu.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > Reviewed-by: Gavin Shan <gshan@redhat.com>
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"); }