From mboxrd@z Thu Jan  1 00:00:00 1970
From: Anthony Liguori <aliguori@linux.vnet.ibm.com>
Subject: Re: [Qemu-devel] [PATCH 28/35] kvm: x86: Introduce kvmclock device
 to save/restore its state
Date: Wed, 19 Jan 2011 10:54:10 -0600
Message-ID: <4D371732.5040901@linux.vnet.ibm.com>
References: <cover.1294336601.git.mtosatti@redhat.com> <db8685e3925e7a5593e3f96ae703e1d19ef2fb0b.1294336601.git.mtosatti@redhat.com> <4D2B6CB5.9050602@codemonkey.ws> <4D2B74D8.4080309@web.de> <4D2B8662.9060909@web.de> <m339ozwzvj.fsf@blackfin.pond.sub.org> <4D2C60FB.7030009@linux.vnet.ibm.com> <4D2D80ED.8030405@redhat.com> <4D2D82EE.20002@siemens.com> <4D35A39A.8000801@siemens.com> <4D35ABF8.9050700@linux.vnet.ibm.com> <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> <m37he1nimc.fsf@blackfin.pond.sub.org>
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Cc: Gerd Hoffmann <kraxel@redhat.com>,
	"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
	Jan Kiszka <jan.kiszka@siemens.com>,
	Glauber Costa <glommer@redhat.com>,
	Marcelo Tosatti <mtosatti@redhat.com>,
	"qemu-devel@nongnu.org" <qemu-devel@nongnu.org>,
	Avi Kivity <avi@redhat.com>
To: Markus Armbruster <armbru@redhat.com>
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On 01/19/2011 07:11 AM, Markus Armbruster wrote:
> Gerd Hoffmann<kraxel@redhat.com>  writes:
>
>    
>> 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.  Once q35 finally
>> arrives this will change of course.
>>      
> As far as I know, libvirt does it already.
>    

I think that's a bad idea from a forward compatibility perspective.

Regards,

Anthony Liguori



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Date: Wed, 19 Jan 2011 10:54:10 -0600
From: Anthony Liguori <aliguori@linux.vnet.ibm.com>
MIME-Version: 1.0
Subject: Re: [Qemu-devel] [PATCH 28/35] kvm: x86: Introduce kvmclock device
	to save/restore its state
References: <cover.1294336601.git.mtosatti@redhat.com>
	<db8685e3925e7a5593e3f96ae703e1d19ef2fb0b.1294336601.git.mtosatti@redhat.com>
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	<4D2C60FB.7030009@linux.vnet.ibm.com>
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	<4D35A39A.8000801@siemens.com>
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To: Markus Armbruster <armbru@redhat.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>, "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>, Gerd Hoffmann <kraxel@redhat.com>, Avi Kivity <avi@redhat.com>

On 01/19/2011 07:11 AM, Markus Armbruster wrote:
> Gerd Hoffmann<kraxel@redhat.com>  writes:
>
>    
>> 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.  Once q35 finally
>> arrives this will change of course.
>>      
> As far as I know, libvirt does it already.
>    

I think that's a bad idea from a forward compatibility perspective.

Regards,

Anthony Liguori