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

[Hanweidong <hanweidong@xxxxxxxxxx>]

> -----Original Message-----
> From: Gordan Bobic [mailto:gordan@xxxxxxxxxx]
> Sent: 2013年5月21日 2:43
> To: George Dunlap
> Cc: Hanweidong; Stefano Stabellini; xudong.hao@xxxxxxxxx; Yanqiangjun;
> Luonengjun; Wangzhenguo; Yangxiaowei; Gonglei (Arei); Anthony Perard;
> xen-devel@xxxxxxxxxxxxx; xiantao.zhang@xxxxxxxxx
> Subject: Re: [Xen-devel] GPU passthrough issue when VM is configured
> with 4G memory
> 
> I'd also like to stress this is not only an issue for > 4GB of RAM in
> domU - I am seeing the issue with > 2GB of RAM in domU.

What's the total mmio size of you domU? When RAM of domU overlaps with 
pci_mem_start, hvmloader will relocate RAM, and it will cause problem due to 
hvmloader and QEMU don't setup the memory layout consistently. I suspect the 
mmio size of your domU is close to 2GB. When you configured RAM > 2G, then RAM 
of your domU overlapped with pci_mem_start, and resulted in failure.

weidong

> 
> Gordan
> 
> On 05/20/2013 12:29 PM, George Dunlap wrote:
> > On 17/05/13 08:10, Hanweidong wrote:
> >> Actually, it's not really related to GPU passthrough. You can
> >> reproduce it when a VM has a big pci hole size (such as 512MB), e.g.
> >> create a VM with a virtual device which has a 512MB pci BAR.
> >
> > It seems like this is probably an artchitectural thing that will
> require
> > someone familiar with qemu to sort out.  Anthony and Stefano, could
> one
> > of you two step up to getting it sorted by 4.3?
> >
> >   -George
> >
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@xxxxxxxxxxxxx
> > http://lists.xen.org/xen-devel

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