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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 05250C04AB6 for ; Tue, 28 May 2019 12:28:05 +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 D0D25208C3 for ; Tue, 28 May 2019 12:28:04 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D0D25208C3 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.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]:33939 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hVbD1-0005M1-Vt for qemu-devel@archiver.kernel.org; Tue, 28 May 2019 08:28:04 -0400 Received: from eggs.gnu.org ([209.51.188.92]:51282) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hVbC0-0004ml-Jt for qemu-devel@nongnu.org; Tue, 28 May 2019 08:27:01 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hVbBz-0007YE-BP for qemu-devel@nongnu.org; Tue, 28 May 2019 08:27:00 -0400 Received: from mx1.redhat.com ([209.132.183.28]:56904) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hVbBz-0007U0-6m for qemu-devel@nongnu.org; Tue, 28 May 2019 08:26:59 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id D85B930C0DCE; Tue, 28 May 2019 12:26:33 +0000 (UTC) Received: from localhost (unknown [10.43.2.182]) by smtp.corp.redhat.com (Postfix) with ESMTP id 77D795D71A; Tue, 28 May 2019 12:26:32 +0000 (UTC) Date: Tue, 28 May 2019 14:26:27 +0200 From: Igor Mammedov To: Wei Yang Message-ID: <20190528142627.6841e91a@redhat.com> In-Reply-To: <20190528013548.GA8813@richard> References: <20190411071739.22889-1-richardw.yang@linux.intel.com> <20190527142114.521ab953@redhat.com> <20190528013548.GA8813@richard> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.45]); Tue, 28 May 2019 12:26:40 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 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: , Cc: pbonzini@redhat.com, thuth@redhat.com, rth@twiddle.net, qemu-devel@nongnu.org, ehabkost@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" 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. 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. So I'd leave the code as it is now, since it doesn't depend on concrete hotplug_handler_pre_plug() implementation and won't break if hotplug_handler_pre_plug() will start consuming resources (which could happen and you won't even notice it since changed code is in piix4/q35 files when reviewing patches). > This is why I suggest to change the order here. No functional issue for > current code. >