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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham 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 3CE2FC28CC0 for ; Thu, 30 May 2019 00:29:26 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id F0CB4243A5 for ; Thu, 30 May 2019 00:29:25 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org F0CB4243A5 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([127.0.0.1]:47231 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hW8we-0002t3-U7 for qemu-devel@archiver.kernel.org; Wed, 29 May 2019 20:29:24 -0400 Received: from eggs.gnu.org ([209.51.188.92]:41018) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hW8vl-0002aT-Fe for qemu-devel@nongnu.org; Wed, 29 May 2019 20:28:30 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hW8vk-00024y-6X for qemu-devel@nongnu.org; Wed, 29 May 2019 20:28:29 -0400 Received: from mga03.intel.com ([134.134.136.65]:65534) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hW8vj-00023g-UV for qemu-devel@nongnu.org; Wed, 29 May 2019 20:28:28 -0400 X-Amp-Result: UNSCANNABLE X-Amp-File-Uploaded: False Received: from fmsmga006.fm.intel.com ([10.253.24.20]) by orsmga103.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 29 May 2019 17:28:25 -0700 X-ExtLoop1: 1 Received: from richard.sh.intel.com (HELO localhost) ([10.239.159.54]) by fmsmga006.fm.intel.com with ESMTP; 29 May 2019 17:28:23 -0700 Date: Thu, 30 May 2019 08:27:54 +0800 From: Wei Yang To: Igor Mammedov Message-ID: <20190530002754.GA24526@richard> References: <20190411071739.22889-1-richardw.yang@linux.intel.com> <20190527142114.521ab953@redhat.com> <20190528013548.GA8813@richard> <20190528142627.6841e91a@redhat.com> <20190529003214.GA24428@richard> <20190529105750.696fe6d2@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190529105750.696fe6d2@redhat.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 134.134.136.65 Subject: Re: [Qemu-devel] [PATCH] hw/i386/pc: check apci hotplug capability before nvdimm's X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Wei Yang Cc: thuth@redhat.com, ehabkost@redhat.com, qemu-devel@nongnu.org, Wei Yang , pbonzini@redhat.com, rth@twiddle.net Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Wed, May 29, 2019 at 10:57:50AM +0200, Igor Mammedov wrote: >On Wed, 29 May 2019 08:32:14 +0800 >Wei Yang wrote: > >> On Tue, May 28, 2019 at 02:26:27PM +0200, Igor Mammedov wrote: >> >On Tue, 28 May 2019 09:35:48 +0800 >> >Wei Yang wrote: >> > >> >> On Mon, May 27, 2019 at 02:21:14PM +0200, Igor Mammedov wrote: >> >> >On Thu, 11 Apr 2019 15:17:39 +0800 >> >> >Wei Yang wrote: >> >> > >> >> >> pc_memory_pre_plug() is called during hotplug for both pc-dimm and >> >> >> nvdimm. This is more proper to check apci hotplug capability before >> >> >> check nvdimm specific capability. >> >> >not sure what this about. >> >> >Currently we are checking if ACPI is enabled >> >> > if (!pcms->acpi_dev || !acpi_enabled) { ... >> >> >before nvdimm check and it looks better to me that we cancel >> >> >nvdimm hotplug earlier than passing it to >> >> > hotplug_handler_pre_plug(pcms->acpi_dev, dev, &local_err) >> >> >with this patch ACPI device handler will be called before >> >> >nvdimm check happens, so it's +1 unnecessary call chain in >> >> >the case of nvdimm, which I'd rather not have. >> >> > >> >> >Are there any issues with current call flow? >> >> >(commit message doesn't really explaining why we need this patch) >> >> > >> >> >> >> My idea is to check more generic requirement and then specific one. >> >> >> >> For example, the call flow looks like this: >> >> >> >> pc_memory_pre_plug >> >> >> >> piix4_device_pre_plug_cb | ich9_pm_device_pre_plug_cb >> >> if (object_dynamic_cast(OBJECT(dev), TYPE_PC_DIMM) && >> >> !lpc->pm.acpi_memory_hotplug.is_enabled) >> >> >> >> if (is_nvdimm && !ms->nvdimms_state->is_enabled) >> >> >> >> >> >> In hotplug_handler_pre_plug(), it checks the acpi hotplug capability. And then >> >> if it has memory hotplug capability and is nvdimm, we check whether nvdimm is >> >> enabled. >> > >> >I don't think pc_memory_pre_plug() should rely on what hotplug_handler_pre_plug() >> >checks or does. Similarly the later is taking care of whatever piix4 needs to care >> >and shouldn't care about what machine code does. >> > >> >> Agree. It is not proper to let hotplug_handler_pre_plug() take care about >> machine code. >> >> >Moreover when hotplug_handler_pre_plug() starts to reserve resources, then >> >if you move check as suggested you'd need to rollback all that >> >hotplug_handler_pre_plug() done to gracefully abort hotplug. >> > >> >> Confused. >> >> hotplug_handler_pre_plug() doesn't reserve resources. > > >it's not currently, but if it would it would not work with your patch properly >or break unexpectedly since whoever would change hotplug_handler_pre_plug() >might not notice that machine code need to be taken care of. > >Try to consider devices and machine as separate libraries. Which should >in reasonable limits be independent and work through documented interfaces. >In that case likehood of breaking something would be less than relying on >current code impl./call order with implicit inter-dependencies. > So the logic here is check machine then device, right? I think this is reasonable. To be honest, this rule is not that obvious. Anyway, I think what you mentioned make sense. Thanks -- Wei Yang Help you, Help me