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 lists.gnu.org (lists.gnu.org [209.51.188.17]) (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 62895C46CD4 for ; Thu, 21 Dec 2023 06:35:47 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1rGCe6-0004Ek-Gr; Thu, 21 Dec 2023 01:35:02 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rGCe5-0004ES-4h for qemu-devel@nongnu.org; Thu, 21 Dec 2023 01:35:01 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rGCe3-0000fz-DH for qemu-devel@nongnu.org; Thu, 21 Dec 2023 01:35:00 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1703140497; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=6bC0aeV+aAOc9MY6fRzWq66WxPe5y8huMHlMzC+ENAU=; b=eCpVXCIb98EA+7tL70MWUZsLDJzgEWS+fpgz010TdOGUwCWneFd9TJU4G2S+09hqXWeH6G rf50DieHSB/JnB5e7bkjdhVhaeHRodH0ETymqmgae7qR7Vw7DCg6e4Xugeq9J/7ofs7tlE QVdoK7/vYR6bTCp5yF+PkvJOotsz5ik= Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-158-jsXtEf-lOKWeVRvuaelzWA-1; Thu, 21 Dec 2023 01:34:55 -0500 X-MC-Unique: jsXtEf-lOKWeVRvuaelzWA-1 Received: from smtp.corp.redhat.com (int-mx10.intmail.prod.int.rdu2.redhat.com [10.11.54.10]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 7B27D3869142; Thu, 21 Dec 2023 06:34:55 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.39.192.129]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 17D31492BFA; Thu, 21 Dec 2023 06:34:55 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id EFCBE21E6920; Thu, 21 Dec 2023 07:34:53 +0100 (CET) From: Markus Armbruster To: Zhao Liu Cc: Akihiko Odaki , Paolo Bonzini , Daniel P. =?utf-8?Q?Berrang=C3=A9?= , Eduardo Habkost , qemu-devel@nongnu.org Subject: Re: [PATCH v2] qdev: Report an error for machine without HotplugHandler In-Reply-To: (Zhao Liu's message of "Thu, 21 Dec 2023 00:46:03 +0800") References: <20231210-bus-v2-1-34ebf5726fa0@daynix.com> <87h6kpgrl7.fsf@pond.sub.org> <8734vzsj6k.fsf@pond.sub.org> <87y1dpgvim.fsf@pond.sub.org> Date: Thu, 21 Dec 2023 07:34:53 +0100 Message-ID: <871qbg9i7m.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.10 Received-SPF: pass client-ip=170.10.133.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.063, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Zhao Liu writes: > Hi Markus, > > On Wed, Dec 20, 2023 at 08:53:21AM +0100, Markus Armbruster wrote: >> Date: Wed, 20 Dec 2023 08:53:21 +0100 >> From: Markus Armbruster >> Subject: Re: [PATCH v2] qdev: Report an error for machine without >> HotplugHandler >> >> Having hotpluggable = true when the device cannot be hot-plugged is >> *wrong*. You might be able to paper over the wrongness so the code >> works anyway, but nothing good can come out of lying to developers >> trying to understand how the code works. >> >> Three ideas to avoid the lying: >> >> 1. default hotpluggable to bus_type != NULL. >> >> 2. assert(dc->bus_type || !dc->hotpluggable) in a suitable spot. >> >> 3. Change the meaning of hotpluggable, and rename it to reflect its new >> meaning. Requires a careful reading of its uses. I wouldn't go there. >> > > What about 4 (or maybe 3.1) - droping this hotpluggable flag and just use a > helper (like qbus) to check if device is hotpluggable? > > This removes the confusion of that flag and also reduces the number of > configuration items for DeviceState that require developer attention. > A simple helper is as follows: > > static inline bool qdev_is_hotpluggable(DeviceState *dev) > { > /* > * Many Machines don't implement qdev_hotplug_allowed(). > * > * TODO: Once all of them complete missing qdev_hotplug_allowed(), > * use qdev_hotplug_allowed() here. > */ > bool hotpluggable = !!qdev_get_machine_hotplug_handler(dev); > > if (!hotpluggable && dev->parent_bus) { > hotpluggable = qbus_is_hotpluggable(dev->parent_bus); > } > > return hotpluggable; > } Worth exploring, I think.