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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 65BFEEED61A for ; Fri, 15 Sep 2023 17:12:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:In-Reply-To:References: Message-ID:Date:Subject:CC:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=nNusjmzSvMbHPbbecnyveY7EHaN//kceGvcInFSo7D4=; b=iZ+Pe1zOnB23Ln pQf1SEEMmWV9CimBTTmznrCwXnB/Tsk9G1jaq3k6BtY1Y+oC76Wa4XQCt7qDXeknj8mNvEanbYVLm ZX5eeqsN6VsNJu/oz0NCrzNiGgg2kqHrfO6ndN1bMHljctANFRY534PoOgHRW8SfdBgCvDuW0b9O1 Tz9HkMhpVWll0+7CyHYlQF/SwEBirInkWyvTPECfPtY0SC3cgnfcdjSEPpE5G/YIr86/ZPi0A5CXy BUnEcvFmhUrBMNqRFvm23xi0ItMMzeARBGp/1U5jI/Yw+ca0uc8Jct7qNOj+9Xs3sjSi6lpaZGRTm ju2Tis0Z+RQ3JrzlJAmg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1qhCMf-00B7Ps-2H; Fri, 15 Sep 2023 17:12:21 +0000 Received: from frasgout.his.huawei.com ([185.176.79.56]) by bombadil.infradead.org with esmtps (Exim 4.96 #2 (Red Hat Linux)) id 1qhCMc-00B7PD-37; Fri, 15 Sep 2023 17:12:20 +0000 Received: from lhrpeml500005.china.huawei.com (unknown [172.18.147.207]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4RnLM908Zwz6K5wf; Sat, 16 Sep 2023 01:11:33 +0800 (CST) Received: from lhrpeml500001.china.huawei.com (7.191.163.213) 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; Fri, 15 Sep 2023 18:12:12 +0100 Received: from lhrpeml500001.china.huawei.com ([7.191.163.213]) by lhrpeml500001.china.huawei.com ([7.191.163.213]) with mapi id 15.01.2507.031; Fri, 15 Sep 2023 18:12:12 +0100 From: Salil Mehta To: Jonathan Cameron CC: Russell King , "Rafael J. Wysocki" , Ard Biesheuvel , James Morse , "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" , "Jean-Philippe Brucker" , "jianyong.wu@arm.com" , "justin.he@arm.com" Subject: RE: [RFC PATCH v2 27/35] ACPICA: Add new MADT GICC flags fields [code first?] Thread-Topic: [RFC PATCH v2 27/35] ACPICA: Add new MADT GICC flags fields [code first?] Thread-Index: AQHZ5mDqpYLh+nkhC0mj9mPBt3XEBLAZ5MMAgAB0lICAAAsFgIAAEfIQgADzSoCAABq9gIAAG4DQgAA3wICAACNmMP//+zYAgAArSrA= Date: Fri, 15 Sep 2023 17:12:12 +0000 Message-ID: <62c89f1c03f34f2796244ba83c08adbb@huawei.com> References: <20230913163823.7880-1-james.morse@arm.com> <20230913163823.7880-28-james.morse@arm.com> <20230914155459.00002dba@Huawei.com> <80e36ff513504a0382a1cbce83e42295@huawei.com> <9e327ad1128045fa80eebf327abaa8f0@huawei.com> <20230915163238.000054c8@Huawei.com> In-Reply-To: <20230915163238.000054c8@Huawei.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.126.174.239] MIME-Version: 1.0 X-CFilter-Loop: Reflected X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230915_101219_307866_B09BACD7 X-CRM114-Status: GOOD ( 46.43 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Jonathan, > From: Jonathan Cameron > Sent: Friday, September 15, 2023 4:33 PM > To: Salil Mehta > Cc: Russell King ; Rafael J. Wysocki > ; Ard Biesheuvel ; James Morse > ; 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; Jean- > Philippe Brucker ; jianyong.wu@arm.com; > justin.he@arm.com > Subject: Re: [RFC PATCH v2 27/35] ACPICA: Add new MADT GICC flags fields > [code first?] > > On Fri, 15 Sep 2023 16:17:21 +0100 > Salil Mehta wrote: > > > Hi Russel, > > Thanks for highlighting your concerns. > > > > > From: Russell King > > > Sent: Friday, September 15, 2023 2:43 PM > > > To: Salil Mehta > > > Cc: Rafael J. Wysocki ; Ard Biesheuvel > > > ; Jonathan Cameron ; James > > > Morse ; 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; Jean-Philippe Brucker > > philippe@linaro.org>; jianyong.wu@arm.com; justin.he@arm.com > > > Subject: Re: [RFC PATCH v2 27/35] ACPICA: Add new MADT GICC flags fields > > > [code first?] > > > > > > On Fri, Sep 15, 2023 at 09:34:46AM +0000, Salil Mehta wrote: > > > > > > Note that the ACPI spec says enabled + online-capable isn't defined. > > > > > > > > > > > > "The information conveyed by this bit depends on the value of the > > > > > > Enabled bit. If the Enabled bit is set, this bit is reserved and > > > > > > must be zero." > > > > > > > > > > > > So, if x86 is doing something with the enabled && online-capable > > > > > > state (other than ignoring the online-capable) then technically it > > > > > > is doing something that the spec doesn't define > > > > > > > > > > And so it is wrong. > > > > > > > > Or maybe, specification has not been updated yet. code-first? > > > > > > What is the point in speculating. If you want to speculate about it, > > > fine, but please don't use speculation as a reason that "oh we need > > > to sort this out before we can merge the patches". > > > > [already replied in other thread but repeating it here] > > > > Sorry, I am not aware but I was suggesting this. Can we have this > > done for ARM first because there is a legitimate use-case. This > > can be done in parallel while other patches are getting reviewed. > > It would be great if they get accepted even in the current form. > > > > > > > This is precisely why engineers are bad at producing products. They > > > like to continually tweak the design, and the design never gets out > > > the door. You need someone who is a project manager to tell engineers > > > when to stop. Without a project manager to do that, eventually the > > > project fades into insignificance because it becomes no longer relevant > > > or has its funding cut. > > > > > > Hotplug VCPU on aarch64 feels exactly like that - it seems to be an > > > engineer project that is just going to for-ever rumble on and never > > > actually see the light of day. > > > > > > Sometimes things are not in single persons control. Yes, it is > > frustrating, I do understand that. > > > > > > > So please - stop speculating and lets get vCPU hotplug *actually* > > > delivered and usable. Even if it's not 100% perfect. > > > > We need to decide what is the criteria of acceptability and it can > > vary across organizations. It depends upon internal requirements. > > The issues what I pointed are, > > > > 1. Legacy OS will not boot on latest platform with hotplug support. > > - Try running older windows on ARM platform with hotplug support. > > - older windows will only see boot cpu with online-capable bit. > > - Will windows use _OSC to check compatibility? > > - We have verified this with older Linux and it only shows 1 CPU. > > 2. Hot(un)plug of cold-booted CPUs. > > - Its use-case is subjective. Maybe you can throw light on this. > > > > With current composition of bits both 1 & 2 cannot be supported > > simultaneously. > > > > It is perfectly okay to live with them while clearly indicating > > what we intend to support or are in process of supporting it. > > But we do need an open discussion about how to proceed. This is > > to avoid surprises later on. > > > > BTW, I am just trying to make every one aware of the problems. > > Step 1 - just allow growing (and shrinking back to initial > enabled cpus). That is fine with current specification and legacy > OS. We only assume CPUs that are hotplugged can later be removed. > That covers most use cases. Yes, we can do that for a moment (at least in qemu) and then not allow unplugging vCPUs which were cold plugged or allow it as a debugging feature but splash a warning. > So what effectively what Russell said. Enable what we can with > the specifications as they stand before getting distracted by > modifying them (again). Yes, agreed. Idea was to clearly highlight them. These can be discussed as part of separate thread in parallel - absolutely! Thanks Salil. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel