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

[Hanweidong <hanweidong@xxxxxxxxxx>]

> -----Original Message-----
> From: Pasi KÃrkkÃinen [mailto:pasik@xxxxxx]
> Sent: 2013å3æ5æ 21:21
> To: Hanweidong
> Cc: Gonglei (Arei); xen-devel@xxxxxxxxxxxxx; Yangxiaowei; Yanqiangjun;
> Luonengjun; Wangzhenguo
> Subject: Re: [Xen-devel] GPU passthrough issue when VM is configured
> with 4G memory
> 
> On Tue, Mar 05, 2013 at 12:44:36PM +0000, Hanweidong wrote:
> > >
> > > >    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:
> > > >
> > >
> > > I don't think qemu-upstream has GPU/VGA passthrough support yet.
> >
> > Qemu-upstream already supports GPU/VGA pass-through.
> >
> 
> Really? With Xen?
> I haven't seen the patches..

Yes, QEMU-upstream doesn't have VGA pass-through. We just assign GPU as
a common pci device to VM, and it can work after loading driver.

> 
> > If we configure VM memory with 3G, GPU pass-through works well.
> >
> 
> Right..
> 
> 
> > >
> > >
> > > >           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().
> > > >
> > > >           In the failure case (VM memory is 4G), I used "memtest"
> to
> > > check
> > > >    memory of the VM which configured with more than 4G memory,
> the last
> > > 256M
> > > >    has errors.
> > > >
> > > >
> > > >
> > > >    BTW, Xen 4.1.2 doesn't have this issue.
> > > >
> > >
> > > I assume with Xen 4.1.2 you're using qemu-traditional.. ?
> >
> >  Yes, we tried Xen 4.1.2 with qemu-traditional.
> >
> > >
> > > Try using qemu-traditional also with xen-unstable.
> > >
> >
> > OK, we will have a try. But seems it's not qemu's problem, we can
> make GPU pass-through succeed if we didn't do
> > XENMAPSPACE_gmfn_range hypercall in pci_setup() with 4G memory.
> >
> 
> Yep. Please send patches when you figure it out!
> 

We found GPU pass-through worked if using qemu-traditional. So it looks 
there is some relationship between XENMAPSPACE_gmfn_range hypercall and 
qemu. In addition, we found it's fine to assign GPU to Win7 32bit guest
 with 4G memory.

--Weidong

> 
> -- Pasi
> 
> 
> 
> > --Weidong
> >
> > > -- Pasi
> > >
> > > >
> > > >
> > > >    Any ideas about this issue? Thanks in advance.
> > > >
> > > >
> > >
> > > > _______________________________________________
> > > > Xen-devel mailing list
> > > > Xen-devel@xxxxxxxxxxxxx
> > > > http://lists.xen.org/xen-devel
> >
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