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

> -----Original Message-----
> From: dunlapg@xxxxxxxxx [mailto:dunlapg@xxxxxxxxx] On Behalf Of George
> Dunlap
> Sent: 2013年3月5日 20:59
> To: Gonglei (Arei)
> Cc: xen-devel@xxxxxxxxxxxxx; Yangxiaowei; Yanqiangjun; Luonengjun;
> Wangzhenguo; Hanweidong
> Subject: Re: [Xen-devel] GPU passthrough issue when VM is configured
> with 4G memory
> On Mon, Mar 4, 2013 at 8:10 AM, Gonglei (Arei) <arei.gonglei@xxxxxxxxxx>
> wrote:
> > Hi,all
> >
> > I have tried to passthrough GPU card(Nvidia quadro 4000) on the
> latest Xen
> > unstable version (QEMU is using Qemu-upsteam-unstable, not
> traditional
> > Qemu). This issue as below:
> >
> >        Windows7 64-bit guest will blue screen when GPU passthrough
> configure
> > 4g memory,blue screen code is 50, and SUSE 11 64-bit guest will
> always stay
> > at the grub screen.  I noticed that it will relocate RAM that
> overlaps PCI
> > space in pci_setup()(tools/hvmloader/pci.c). If VM memory is
> configured with
> > 3G, it won't cause relocate RAM that overlaps PCI space in
> pci_setup(), and
> > GPU pass-through is no problem. So it seems this issue is related to
> > "relocate RAM" in pci_setup().
> So one issue XenServer found with passing through GPUs is that there
> are bugs in some PCI bridges that completely break VT-d.  The issue
> was that if the *guest* physical address space overlapped the *host*
> physical address of a different device, that the PCI bridges would
> send traffic from the passed-through card intended for the guest to
> another card instead.  The work-around was to make the hole in the
> guest MMIO space the same size as the host MMIO hole.  I'm not sure if
> that made it upstream or not -- let me check...
Hi George,

Could you post your patch and let us have a try with it? Thanks!

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