Hacking QEMU/KVM to use unused graphics adapters

Hacking QEMU/KVM to use unused graphics adapters

[Anthony de Almeida Lopes]

I was curious if anyone thinks that it may be possible to get a 
KVM-patched QEMU to use a real video card? For example, let's say I had 
a second video card. Is QEMU/kvm a codebase which would support hacking 
in the ability to utilize this second video card (one not utilized by 
the host Linux)? And in the situation of a laptop, would it be possible 
to boot the host Linux in a way that it would not utilize the video 
card, but get a qemu guest to use it?
Theoretically, there's no reason this isn't possible, right?


Thanks,
-  Tony

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Re: Hacking QEMU/KVM to use unused graphics adapters

[Laurent Vivier]

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Anthony de Almeida Lopes wrote:
> I was curious if anyone thinks that it may be possible to get a 
> KVM-patched QEMU to use a real video card? For example, let's say I had 
> a second video card. Is QEMU/kvm a codebase which would support hacking 
> in the ability to utilize this second video card (one not utilized by 
> the host Linux)? And in the situation of a laptop, would it be possible 
> to boot the host Linux in a way that it would not utilize the video 
> card, but get a qemu guest to use it?
> Theoretically, there's no reason this isn't possible, right?

We need something like a "PCI proxy" allowing to route some I/O to virtual PCI
devices and others to real PCI devices. Moreover we must be able to inform host
kernel to not manage a given PCI card (or be able to hot unplug it from host
kernel PCI structures)

Laurent
-- 
---------------- Laurent.Vivier-6ktuUTfB/bM@public.gmane.org  -----------------
"Given enough eyeballs, all bugs are shallow" E. S. Raymond


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Re: Hacking QEMU/KVM to use unused graphics adapters

[Dor Laor]

Laurent Vivier wrote:
>
> Anthony de Almeida Lopes wrote:
> > I was curious if anyone thinks that it may be possible to get a
> > KVM-patched QEMU to use a real video card? For example, let's say I had
> > a second video card. Is QEMU/kvm a codebase which would support hacking
> > in the ability to utilize this second video card (one not utilized by
> > the host Linux)? And in the situation of a laptop, would it be possible
> > to boot the host Linux in a way that it would not utilize the video
> > card, but get a qemu guest to use it?
> > Theoretically, there's no reason this isn't possible, right?
>
> We need something like a "PCI proxy" allowing to route some I/O to 
> virtual PCI
> devices and others to real PCI devices. Moreover we must be able to 
> inform host
> kernel to not manage a given PCI card (or be able to hot unplug it 
> from host
> kernel PCI structures)
>
There is work in progress for pci pass through capability. Besides PCI it
also required to have pv dma or 1-1 mapping between the guest and the host.
Both will be released in the following month. NIC pass through works but I'm
not sure about the features required from VGA pass through.
Dor.

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Re: Hacking QEMU/KVM to use unused graphics adapters

[Laurent Vivier]

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Dor Laor wrote:
> Laurent Vivier wrote:
>>
>> Anthony de Almeida Lopes wrote:
>> > I was curious if anyone thinks that it may be possible to get a
>> > KVM-patched QEMU to use a real video card? For example, let's say I had
>> > a second video card. Is QEMU/kvm a codebase which would support hacking
>> > in the ability to utilize this second video card (one not utilized by
>> > the host Linux)? And in the situation of a laptop, would it be possible
>> > to boot the host Linux in a way that it would not utilize the video
>> > card, but get a qemu guest to use it?
>> > Theoretically, there's no reason this isn't possible, right?
>>
>> We need something like a "PCI proxy" allowing to route some I/O to
>> virtual PCI
>> devices and others to real PCI devices. Moreover we must be able to
>> inform host
>> kernel to not manage a given PCI card (or be able to hot unplug it
>> from host
>> kernel PCI structures)
>>
> There is work in progress for pci pass through capability. Besides PCI it
> also required to have pv dma or 1-1 mapping between the guest and the host.
> Both will be released in the following month. NIC pass through works but
> I'm
> not sure about the features required from VGA pass through.
> Dor.

Perhaps if we use host IOMMU we don't need pv DMA ?
How do you say to host to not manage a PCI devices and let the guest managing it ?

Laurent
-- 
---------------- Laurent.Vivier-6ktuUTfB/bM@public.gmane.org  -----------------
"Given enough eyeballs, all bugs are shallow" E. S. Raymond


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Re: Hacking QEMU/KVM to use unused graphics adapters

[Muli Ben-Yehuda]

On Thu, Oct 11, 2007 at 10:40:47AM +0200, Laurent Vivier wrote:

> > There is work in progress for pci pass through capability. Besides
> > PCI it also required to have pv dma or 1-1 mapping between the
> > guest and the host.  Both will be released in the following
> > month. NIC pass through works but I'm not sure about the features
> > required from VGA pass through.  Dor.
> 
> Perhaps if we use host IOMMU we don't need pv DMA ?

Indeed, an IOMMU can provide the 1-1 mapping Dor mentioned above (or
you can have both PV DMA and an IOMMU).

> How do you say to host to not manage a PCI devices and let the guest
> managing it ?

If the host driver is modular, it might be enough to just not load (or
unload) it.

Cheers,
Muli
-- 
SYSTOR 2007 --- 1st Annual Haifa Systems and Storage Conference 2007
http://www.haifa.il.ibm.com/Workshops/systor2007/

Virtualization workshop: Oct 29th, 2007 | Storage workshop: Oct 30th, 2007

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Re: Hacking QEMU/KVM to use unused graphics adapters

[Anthony de Almeida Lopes]

Muli Ben-Yehuda wrote:
> On Thu, Oct 11, 2007 at 10:40:47AM +0200, Laurent Vivier wrote:
>
>   
>>> There is work in progress for pci pass through capability. Besides
>>> PCI it also required to have pv dma or 1-1 mapping between the
>>> guest and the host.  Both will be released in the following
>>> month. NIC pass through works but I'm not sure about the features
>>> required from VGA pass through.  Dor.
>>>       
>> Perhaps if we use host IOMMU we don't need pv DMA ?
>>     
>
> Indeed, an IOMMU can provide the 1-1 mapping Dor mentioned above (or
> you can have both PV DMA and an IOMMU).
>
>   
>> How do you say to host to not manage a PCI devices and let the guest
>> managing it ?
>>     
>
> If the host driver is modular, it might be enough to just not load (or
> unload) it.
>
> Cheers,
> Muli
>   

Thank you for your responses. I was curious, Dor, where could I take a 
look at this code?
I checked both sets of recent git logs and nothing popped out at me as 
being related. Is it still out-of-tree?

Thanks again,
 - Tony

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Re: Hacking QEMU/KVM to use unused graphics adapters

[Anthony de Almeida Lopes]

I just read the ChangeLogs from kvm-47 to kvm-59 but I didn't notice 
anything that about PCI pass-through or any VGA work. I'm curious how 
things are going and what method was selected to accomplish this 
functionality?
 - Tony

Dor Laor wrote:
> It's still out-of -tree.
> Not for long :)
>
> Anthony de Almeida Lopes wrote:
>> Muli Ben-Yehuda wrote:
>>  
>>> On Thu, Oct 11, 2007 at 10:40:47AM +0200, Laurent Vivier wrote:
>>>
>>>      
>>>>> There is work in progress for pci pass through capability. Besides
>>>>> PCI it also required to have pv dma or 1-1 mapping between the
>>>>> guest and the host.  Both will be released in the following
>>>>> month. NIC pass through works but I'm not sure about the features
>>>>> required from VGA pass through.  Dor.
>>>>>               
>>>> Perhaps if we use host IOMMU we don't need pv DMA ?
>>>>           
>>> Indeed, an IOMMU can provide the 1-1 mapping Dor mentioned above (or
>>> you can have both PV DMA and an IOMMU).
>>>
>>>      
>>>> How do you say to host to not manage a PCI devices and let the guest
>>>> managing it ?
>>>>           
>>> If the host driver is modular, it might be enough to just not load (or
>>> unload) it.
>>>
>>> Cheers,
>>> Muli
>>>       
>>
>> Thank you for your responses. I was curious, Dor, where could I take 
>> a look at this code?
>> I checked both sets of recent git logs and nothing popped out at me 
>> as being related. Is it still out-of-tree?
>>
>> Thanks again,
>>  - Tony
>>
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>>
>>   
>
>


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Re: Hacking QEMU/KVM to use unused graphics adapters

[Dor Laor]

On Wed, 2008-01-16 at 13:05 +0100, Anthony de Almeida Lopes wrote:
> I just read the ChangeLogs from kvm-47 to kvm-59 but I didn't notice 
> anything that about PCI pass-through or any VGA work. I'm curious how 
> things are going and what method was selected to accomplish this 
> functionality?
>  - Tony
> 

First we had plans only for plain PCI pass through and not VGA device
that has some bios unification possible issues.
Second, we have it working (also all the code was sent to the list) but
there's quick an effort to be done in order to merge it into mainline.
We do want it to happen but we have some other issues on our plait.
Nevertheless, if one wants to push it on
we'll be happy to assist.
Regards,
Dor

> Dor Laor wrote:
> > It's still out-of -tree.
> > Not for long :)
> >
> > Anthony de Almeida Lopes wrote:
> >> Muli Ben-Yehuda wrote:
> >>  
> >>> On Thu, Oct 11, 2007 at 10:40:47AM +0200, Laurent Vivier wrote:
> >>>
> >>>      
> >>>>> There is work in progress for pci pass through capability. Besides
> >>>>> PCI it also required to have pv dma or 1-1 mapping between the
> >>>>> guest and the host.  Both will be released in the following
> >>>>> month. NIC pass through works but I'm not sure about the features
> >>>>> required from VGA pass through.  Dor.
> >>>>>               
> >>>> Perhaps if we use host IOMMU we don't need pv DMA ?
> >>>>           
> >>> Indeed, an IOMMU can provide the 1-1 mapping Dor mentioned above (or
> >>> you can have both PV DMA and an IOMMU).
> >>>
> >>>      
> >>>> How do you say to host to not manage a PCI devices and let the guest
> >>>> managing it ?
> >>>>           
> >>> If the host driver is modular, it might be enough to just not load (or
> >>> unload) it.
> >>>
> >>> Cheers,
> >>> Muli
> >>>       
> >>
> >> Thank you for your responses. I was curious, Dor, where could I take 
> >> a look at this code?
> >> I checked both sets of recent git logs and nothing popped out at me 
> >> as being related. Is it still out-of-tree?
> >>
> >> Thanks again,
> >>  - Tony
> >>
> >> ------------------------------------------------------------------------- 
> >>
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> >>
> >>   
> >
> >
> 


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