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Re: [Xen-devel] RE: Xen enviroment consultation

On Mon, May 23, 2011 at 08:54:19AM +0000, Fan, Huaxiang wrote:
> Hi Konrad,
> Thanks, the problem solved when I pass in 'iommu=soft' in the PV guests. 
> Could you elaborate on the link between this option and the problem?

You mean why you need 'iommu=soft' when doing PCI passthrough in PV guests? I 
suggest you google for Xen SWIOTLB. I probably wrote the explanation in one of 
links - but I don't remember which one.

> And this option also raised another minor issue. For example, I have 4 domus, 
> and the PCI passthru situation as below:
> Domu_name  passthru_pci_number_in_dom0
> 1           04:00.0 04:00.1
> 2           02:00.0 02:00.1
> 3           01:00.1
> 4           <none>
> I passed in 'iommu=soft' in 1,2,3 domu. The order I should boot the domus is 
> 1,2,3,4. Otherwise, the domu might fail to boot due to the error:
> Pciback 0000:04:00.1: device has been assigned to another domain! 
> Over-writing the ownership, but beware.

Looks like a bug in the pciback code. It somehow things that you had 04:00.1 
assigned to another
domain and hadn't cleaned it up probably.

For right I would ignore that - as it is not failing the bootup - just warning 
you. And are
you using xen-pciback.hide as an option to "hide" the devices from Dom0?

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