From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Daniel P. Berrange" <berrange@redhat.com>
Subject: Re: [Qemu-devel] [PATCH 28/35] kvm: x86: Introduce kvmclock device
 to save/restore its state
Date: Wed, 19 Jan 2011 17:35:05 +0000
Message-ID: <20110119173505.GK5113@redhat.com>
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>
Reply-To: "Daniel P. Berrange" <berrange@redhat.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=utf-8
Cc: Gerd Hoffmann <kraxel@redhat.com>,
	Jan Kiszka <jan.kiszka@siemens.com>,
	Avi Kivity <avi@redhat.com>,
	Markus Armbruster <armbru@redhat.com>,
	Marcelo Tosatti <mtosatti@redhat.com>,
	Glauber Costa <glommer@redhat.com>,
	"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
	"qemu-devel@nongnu.org" <qemu-devel@nongnu.org>
To: Anthony Liguori <aliguori@linux.vnet.ibm.com>
Return-path: <kvm-owner@vger.kernel.org>
Received: from mx1.redhat.com ([209.132.183.28]:7897 "EHLO mx1.redhat.com"
	rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
	id S1751210Ab1ASRf3 (ORCPT <rfc822;kvm@vger.kernel.org>);
	Wed, 19 Jan 2011 12:35:29 -0500
Content-Disposition: inline
In-Reply-To: <4D37170A.20205@linux.vnet.ibm.com>
Sender: kvm-owner@vger.kernel.org
List-ID: <kvm.vger.kernel.org>

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=<name>.  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

Daniel

From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from [140.186.70.92] (port=58353 helo=eggs.gnu.org)
	by lists.gnu.org with esmtp (Exim 4.43) id 1PfbwO-0003nK-1f
	for qemu-devel@nongnu.org; Wed, 19 Jan 2011 12:35:29 -0500
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <berrange@redhat.com>) id 1PfbwM-0000Mp-Mu
	for qemu-devel@nongnu.org; Wed, 19 Jan 2011 12:35:27 -0500
Received: from mx1.redhat.com ([209.132.183.28]:54117)
	by eggs.gnu.org with esmtp (Exim 4.71)
	(envelope-from <berrange@redhat.com>) id 1PfbwM-0000Mg-Cq
	for qemu-devel@nongnu.org; Wed, 19 Jan 2011 12:35:26 -0500
Date: Wed, 19 Jan 2011 17:35:05 +0000
From: "Daniel P. Berrange" <berrange@redhat.com>
Subject: Re: [Qemu-devel] [PATCH 28/35] kvm: x86: Introduce kvmclock device
	to save/restore its state
Message-ID: <20110119173505.GK5113@redhat.com>
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>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
In-Reply-To: <4D37170A.20205@linux.vnet.ibm.com>
Reply-To: "Daniel P. Berrange" <berrange@redhat.com>
List-Id: qemu-devel.nongnu.org
List-Unsubscribe: <http://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.nongnu.org/archive/html/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <http://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: Anthony Liguori <aliguori@linux.vnet.ibm.com>
Cc: "kvm@vger.kernel.org" <kvm@vger.kernel.org>, Jan Kiszka <jan.kiszka@siemens.com>, Glauber Costa <glommer@redhat.com>, Marcelo Tosatti <mtosatti@redhat.com>, Markus Armbruster <armbru@redhat.com>, "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>, Gerd Hoffmann <kraxel@redhat.com>, Avi Kivity <avi@redhat.com>

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=<name>.  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

Daniel