From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=41057 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1Pfc3A-0006hA-1v for qemu-devel@nongnu.org; Wed, 19 Jan 2011 12:42:29 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Pfc38-0001f9-IW for qemu-devel@nongnu.org; Wed, 19 Jan 2011 12:42:27 -0500 Received: from e37.co.us.ibm.com ([32.97.110.158]:54527) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Pfc38-0001er-CP for qemu-devel@nongnu.org; Wed, 19 Jan 2011 12:42:26 -0500 Received: from d03relay02.boulder.ibm.com (d03relay02.boulder.ibm.com [9.17.195.227]) by e37.co.us.ibm.com (8.14.4/8.13.1) with ESMTP id p0JHdugc018998 for ; Wed, 19 Jan 2011 10:39:56 -0700 Received: from d03av01.boulder.ibm.com (d03av01.boulder.ibm.com [9.17.195.167]) by d03relay02.boulder.ibm.com (8.13.8/8.13.8/NCO v9.1) with ESMTP id p0JHgO6q256978 for ; Wed, 19 Jan 2011 10:42:24 -0700 Received: from d03av01.boulder.ibm.com (loopback [127.0.0.1]) by d03av01.boulder.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id p0JHgNgI027795 for ; Wed, 19 Jan 2011 10:42:23 -0700 Message-ID: <4D37227A.8080904@linux.vnet.ibm.com> Date: Wed, 19 Jan 2011 11:42:18 -0600 From: Anthony Liguori MIME-Version: 1.0 Subject: Re: [Qemu-devel] [PATCH 28/35] kvm: x86: Introduce kvmclock device to save/restore its state References: <4D35B521.3090601@siemens.com> <4D35B6DD.1020005@linux.vnet.ibm.com> <4D35B963.7000605@siemens.com> <4D35BA22.7060602@linux.vnet.ibm.com> <4D35BD30.1060900@siemens.com> <4D35C1CE.10509@linux.vnet.ibm.com> <4D35C648.7050809@siemens.com> <4D35C92D.7030000@linux.vnet.ibm.com> <4D36B362.70202@redhat.com> <4D37170A.20205@linux.vnet.ibm.com> <20110119173505.GK5113@redhat.com> In-Reply-To: <20110119173505.GK5113@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Daniel P. Berrange" Cc: "kvm@vger.kernel.org" , Jan Kiszka , Glauber Costa , Marcelo Tosatti , Markus Armbruster , "qemu-devel@nongnu.org" , Gerd Hoffmann , Avi Kivity On 01/19/2011 11:35 AM, Daniel P. Berrange wrote: > On Wed, Jan 19, 2011 at 10:53:30AM -0600, Anthony Liguori wrote: > >> On 01/19/2011 03:48 AM, Gerd Hoffmann wrote: >> >>> On 01/18/11 18:09, Anthony Liguori wrote: >>> >>>> On 01/18/2011 10:56 AM, Jan Kiszka wrote: >>>> >>>>> >>>>>> The device model topology is 100% a hidden architectural detail. >>>>>> >>>>> This is true for the sysbus, it is obviously not the case for PCI and >>>>> similarly discoverable buses. There we have a guest-explorable topology >>>>> that is currently equivalent to the the qdev layout. >>>>> >>>> But we also don't do PCI passthrough so we really haven't even explored >>>> how that maps in qdev. I don't know if qemu-kvm has attempted to >>>> qdev-ify it. >>>> >>> It is qdev-ified. It is a normal pci device from qdev's point of view. >>> >>> BTW: is there any reason why (vfio-based) pci passthrough couldn't >>> work with tcg? >>> >>> >>>> The -device interface is a stable interface. Right now, you don't >>>> specify any type of identifier of the pci bus when you create a PCI >>>> device. It's implied in the interface. >>>> >>> Wrong. You can specify the bus you want attach the device to via >>> bus=. This is true for *every* device, including all pci >>> devices. If unspecified qdev uses the first bus it finds. >>> >>> As long as there is a single pci bus only there is simply no need >>> to specify it, thats why nobody does that today. >>> >> Right. In terms of specifying bus=, what are we promising re: >> compatibility? Will there always be a pci.0? If we add some >> PCI-to-PCI bridges in order to support more devices, is libvirt >> support to parse the hierarchy and figure out which bus to put the >> device on? >> > The answer to your questions probably differ depending on > whether '-nodefconfig' and '-nodefaults' are set on the > command line. If they are set, then I'd expect to only > ever see one PCI bus with name pci.0 forever more, unless > i explicitly ask for more. If they are not set, then you > might expect to see multiple PCI buses by appear by magic > Yeah, we can't promise that. If you use -M pc, you aren't guaranteed a stable PCI bus topology even with -nodefconfig/-nodefaults. Regards, Anthony Liguori > Daniel >