Re: [Xen-devel] GPU passthrough issue when VM is configured with 4G memory / Xen 4.4

[Pasi Kärkkäinen <pasik@xxxxxx>]

Hello,

George: I think this one is missing from the Xen 4.4 status emails? (see below)

On Wed, May 29, 2013 at 05:18:24PM +0100, Stefano Stabellini wrote:
> 
> Thank you very much for your detailed analysis of the problem.
> 
> After reading this, I wonder how is possible that qemu-xen-traditional
> does not have this issue, considering that AFAIK there is no way for
> hvmloader to tell qemu-xen-traditional where the PCI hole starts.
> 
> The only difference between upstream QEMU and qemu-xen-traditional is
> that the former would start the PCI hole at 0xf0000000 while the latter
> would start the PCI hole at 0xe0000000.
> 
> So I would expect that your test, where hvmloader is updating the PCI
> hole region to start at 0x80000000, would fail on qemu-xen-traditional
> too.
> 
> Of course having the PCI hole starting unconditionally at 0xf0000000
> makes it much easier to run into problems than starting it at
> 0xe0000000.
> 
> 
> Assuming that everything above is correct, this is what I would do:
> 
> 1) modify upstream QEMU to start the PCI hole at 0xe0000000, to match
> qemu-xen-unstable in terms of configuration and not to introduce any
> regressions. Do this for the Xen 4.3 release.
> 
> 2) for Xen 4.4 rework the two patches above and improve
> i440fx_update_pci_mem_hole: resizing the pci_hole subregion is not
> enough, it also needs to be able to resize the system memory region
> (xen.ram) to make room for the bigger pci_hole


I think this second part hasn't been done/fixed yet? 
Feel free to correct me if it has been done already :) 

Thanks,

-- Pasi


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