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=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, 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 539BEC432C0 for ; Tue, 3 Dec 2019 22:08:45 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id 03AD020659 for ; Tue, 3 Dec 2019 22:08:44 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="L5pO3lXj" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 03AD020659 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 ([::1]:59402 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1icGLa-00051G-4E for qemu-devel@archiver.kernel.org; Tue, 03 Dec 2019 17:08:42 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:34027) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1icFwI-0002c8-9n for qemu-devel@nongnu.org; Tue, 03 Dec 2019 16:42:35 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1icFu7-0004LS-Ru for qemu-devel@nongnu.org; Tue, 03 Dec 2019 16:40:23 -0500 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:29952 helo=us-smtp-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1icFu7-0004Ak-MZ for qemu-devel@nongnu.org; Tue, 03 Dec 2019 16:40:19 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1575409217; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=oOi89gzNqsTMPqqa7zoMVPrp+8R/hVc7lgq/F85BMvo=; b=L5pO3lXjA1EJUhd48W2jZljuXykSQu5LDY/jw6uZmOQJw7ap0bFBl7AisLHqATCCBzThgp et3AtbJG8F00Nv1hD6damrmmzT7rG2fDVpepC/pxqw1fVPP1gBWFKr8H0MDEKtPmuPJnaa onVV4HmVZNxj4lA8y6vprOSxb3QZ8rA= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-296-vV21BReHPeaps9YTRT40yw-1; Tue, 03 Dec 2019 16:40:15 -0500 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id A143F10054E3; Tue, 3 Dec 2019 21:40:14 +0000 (UTC) Received: from localhost (ovpn-116-90.gru2.redhat.com [10.97.116.90]) by smtp.corp.redhat.com (Postfix) with ESMTP id 3A52D19C68; Tue, 3 Dec 2019 21:40:05 +0000 (UTC) Date: Tue, 3 Dec 2019 18:40:04 -0300 From: Eduardo Habkost To: Peter Maydell Subject: Re: qom device lifecycle interaction with hotplug/hotunplug ? Message-ID: <20191203214004.GS14595@habkost.net> References: <20191128182705.0635d1d4@redhat.com> <20191129132641.4c7da6c5@redhat.com> <20191129200545.GG14595@habkost.net> MIME-Version: 1.0 In-Reply-To: X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-MC-Unique: vV21BReHPeaps9YTRT40yw-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Content-Disposition: inline X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 205.139.110.120 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Damien Hedde , "Michael S. Tsirkin" , QEMU Developers , Stefan Hajnoczi , Paolo Bonzini , Igor Mammedov , Jens Freimann Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" +jfreimann, +mst On Sat, Nov 30, 2019 at 11:10:19AM +0000, Peter Maydell wrote: > On Fri, 29 Nov 2019 at 20:05, Eduardo Habkost wrote= : > > So, to summarize the current issues: > > > > 1) realize triggers a plug operation implicitly. > > 2) unplug triggers unrealize implicitly. > > > > Do you expect to see use cases that will require us to implement > > realize-without-plug? >=20 > I don't think so, but only because of the oddity that > we put lots of devices on the 'sysbus' and claim that > that's plugging them into the bus. The common case of > 'realize' is where one device (say an SoC) has a bunch of child > devices (like UARTs); the SoC's realize method realizes its child > devices. Those devices all end up plugged into the 'sysbus' > but there's no actual bus there, it's fictional and about > the only thing it matters for is reset propagation (which > we don't model right either). A few devices don't live on > buses at all. That's my impression as well. >=20 > > Similarly, do you expect use cases that will require us to > > implement unplug-without-unrealize? >=20 > I don't know enough about hotplug to answer this one: > it's essentially what I'm hoping you'd be able to answer. > I vaguely had in mind that eg the user might be able to > create a 'disk' object, plug it into a SCSI bus, then > unplug it from the bus without the disk and all its data > evaporating, and maybe plug it back into the SCSI > bus (or some other SCSI bus) later ? But I don't know > anything about how we expose that kind of thing to the > user via QMP/HMP. This ability isn't exposed to the user at all. Our existing interfaces are -device, device_add and device_del. We do have something new that sounds suspiciously similar to "unplugged but not unrealized", though: the new hidden device API, added by commit f3a850565693 ("qdev/qbus: add hidden device support"). Jens, Michael, what exactly is the difference between a "hidden" device and a "unplugged" device? --=20 Eduardo