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 X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id EE9FAC433B4 for ; Tue, 18 May 2021 18:50:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BCB0B61261 for ; Tue, 18 May 2021 18:50:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1351658AbhERSwL convert rfc822-to-8bit (ORCPT ); Tue, 18 May 2021 14:52:11 -0400 Received: from szxga06-in.huawei.com ([45.249.212.32]:3023 "EHLO szxga06-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234553AbhERSwK (ORCPT ); Tue, 18 May 2021 14:52:10 -0400 Received: from dggems705-chm.china.huawei.com (unknown [172.30.72.58]) by szxga06-in.huawei.com (SkyGuard) with ESMTP id 4Fl4lQ11xnzmWcC; Wed, 19 May 2021 02:48:34 +0800 (CST) Received: from dggemm751-chm.china.huawei.com (10.1.198.57) by dggems705-chm.china.huawei.com (10.3.19.182) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Wed, 19 May 2021 02:50:49 +0800 Received: from lhreml703-chm.china.huawei.com (10.201.108.52) by dggemm751-chm.china.huawei.com (10.1.198.57) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256) id 15.1.2176.2; Wed, 19 May 2021 02:50:48 +0800 Received: from lhreml703-chm.china.huawei.com ([10.201.68.198]) by lhreml703-chm.china.huawei.com ([10.201.68.198]) with mapi id 15.01.2176.012; Tue, 18 May 2021 19:50:46 +0100 From: Salil Mehta To: Andrew Jones CC: "wangyanan (Y)" , Peter Maydell , "Michael S . Tsirkin" , "Igor Mammedov" , Shannon Zhao , Alistair Francis , David Gibson , "qemu-devel@nongnu.org" , "qemu-arm@nongnu.org" , "Paolo Bonzini" , =?iso-8859-1?Q?Philippe_Mathieu-Daud=E9?= , yangyicong , "Zengtao (B)" , "Song Bao Hua (Barry Song)" , "Wanghaibin (D)" , zhukeqian , yuzenghui , "linux-kernel@vger.kernel.org" , "linuxarm@openeuler.org" Subject: RE: [RFC PATCH v3 4/9] hw/arm/virt: Initialize the present cpu members Thread-Topic: [RFC PATCH v3 4/9] hw/arm/virt: Initialize the present cpu members Thread-Index: AQHXSj7Bs+01wvGUNEWbtmBiG2lmC6rn8VxQgACpzgCAADVmEP///x2AgADF7hA= Date: Tue, 18 May 2021 18:50:46 +0000 Message-ID: <0ff033fa8eac400fade06e6be0a98847@huawei.com> References: <20210516102900.28036-1-wangyanan55@huawei.com> <20210516102900.28036-5-wangyanan55@huawei.com> <6c8f9c3502384f648f30c7381e87dda9@huawei.com> <68883a1b-5303-da13-a051-e909e1d1f71b@huawei.com> <6d8b9142e8a34d1390f2f0b4bfb53a00@huawei.com> <20210518075027.wjpdjvoam7dlzign@gator.home> In-Reply-To: <20210518075027.wjpdjvoam7dlzign@gator.home> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.47.29.209] Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > From: Andrew Jones [mailto:drjones@redhat.com] > Sent: Tuesday, May 18, 2021 8:50 AM > > On Tue, May 18, 2021 at 07:04:51AM +0000, Salil Mehta wrote: > > > From: wangyanan (Y) > > > Sent: Tuesday, May 18, 2021 5:43 AM > > > > > > Hi Salil, > > > > > > On 2021/5/18 4:48, Salil Mehta wrote: > > > >> From: Qemu-arm > > > [mailto:qemu-arm-bounces+salil.mehta=huawei.com@nongnu.org] > > > >> On Behalf Of Yanan Wang > > > >> Sent: Sunday, May 16, 2021 11:29 AM > > > >> To: Peter Maydell ; Andrew Jones > > > >> ; Michael S . Tsirkin ; Igor Mammedov > > > >> ; Shannon Zhao ; Alistair > > > >> Francis ; David Gibson > > > >> ; qemu-devel@nongnu.org; > qemu-arm@nongnu.org > > > >> Cc: Song Bao Hua (Barry Song) ; zhukeqian > > > >> ; yangyicong ; Zengtao (B) > > > >> ; Wanghaibin (D) > ; > > > >> yuzenghui ; Paolo Bonzini ; > > > >> Philippe Mathieu-Daudé > > > >> Subject: [RFC PATCH v3 4/9] hw/arm/virt: Initialize the present cpu members > > > >> > > > >> We create and initialize a cpuobj for each present cpu in > > > >> machvirt_init(). Now we also initialize the cpu member of > > > >> structure CPUArchId for each present cpu in the function. > > > > [...] > > > > > > > >> qdev_realize(DEVICE(cpuobj), NULL, &error_fatal); > > > >> + > > > >> + /* > > > >> + * As ARM cpu hotplug is not supported yet, we initialize > > > >> + * the present cpu members here. > > > >> + */ > > > >> + machine->possible_cpus->cpus[n].cpu = cpuobj; > > > > > > > > when vcpu Hotplug is not supported yet, what necessitates this change now? > > > > > > > The initialization will gives a way to determine whether a CPU is > > > present or not. > > > At least, for now it will be used when generating ACPI tables, e.g. > > > DSDT, MADT. > > > See patch 5 and 6. > > > > yes, but why do you require it now as part of the vcpu topology change? > > > > As-far-as-i-can-see, PPTT table changes(part of patch 5/9) do not require > > this change. Change in Patch 5/9 has also been done in anticipation of > > some future requirement(vcpu Hotplug?). > > > > Please correct me here if I am wrong? > > > > Hi Salil, > > The problem is that we've never required smp.cpus == smp.maxcpus, so > a user could have smp.cpus < smp.maxcpus. We want the topology to match > maxcpus, but only enable cpus. However, if you think we should just not > allow cpus < maxcpus until hot plug is sorted out, then we could discuss > a way of trying to enforce cpus == maxcpus, but I'm not sure how we can > without breaking existing command lines. Hi Andrew, Ideally, if the vcpu Hotplug is not supported the check in the smp_parse() should impose (cpus == maxcpus). This as of now is just a warning of invalid configuration I think. Beside this does not breaks any prior usages which you suggested might happen? Again, this is not a blocking issue from my side but just a humble suggestion. You might want to take a call on this :) Thanks Salil.