Re: [Xen-devel] q35 in xen? vfio in xen?

["Zhang, Eniac" <eniac-xw.zhang@xxxxxx>]

Hi Konrad,

Thanks for your reply.  

Yes, I am aware of the pciback.  Unfortunately it doesn't seem to support pci-e 
passthrough. (I could be wrong here)

There are two reason that I am interested in this.  For one, my project calls 
for pci-e device passthrough, which can't be accomplished with 440fx chipset 
emulation.  Secondly, I feel we ought to move on with the technology.  440fx is 
ancient in computer terms.  Qemu is good and all that, but if it refuses to 
support pci-e natively then it's just a matter of time that it will become 
obsoleted.  The trend is clear that pci-e is taking over the world.

Regards/Eniac

-----Original Message-----
From: Konrad Rzeszutek Wilk [mailto:konrad.wilk@xxxxxxxxxx] 
Sent: Friday, February 21, 2014 2:50 PM
To: Zhang, Eniac
Cc: xen-devel@xxxxxxxxxxxxx
Subject: Re: [Xen-devel] q35 in xen? vfio in xen?

On Fri, Feb 21, 2014 at 09:41:39PM +0000, Zhang, Eniac wrote:
> Hi all,
> 
> I am playing with q35 chipset in qemu (1.6.1).  It seems we can't enable q35 
> machine under xen yet.  I made a few quick hacks which all fail miserably 
> (linux kernel oops and window BSOD).  I was wondering why this hasn't been 
> done (q35 was introduced into qemu in 2009).
> 
> Next question, vfio works very well for me in standalone qemu (with Linux 
> host handling iommu), but is that supported under xen?  I haven't tried 
> anything there yet because my gut-feeling is that it won't work.  Because 
> passing vfio device to qemu can only be done on qemu commandline, and xen is 
> not aware of this passing through device, thus not able to make iommu 
> arrangement for this device.  Am I on the right track here?

Yes and no. VFIO won't work - but QEMU does do PCI passthrough under Xen. It 
uses a different mechanism (and you need to bind the device to pciback).

> 
> I am interested in implementing both these two features.  I'd like to connect 
> with anyone who's already on this so we don't duplicate the efforts.

What do you need Q35 for?

> 
> Regards/Eniac

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