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

[Matthias <matthias.kannenberg@xxxxxxxxxxxxxx>]

I can recreate the issue:

Whereas xen-unstable does VGA passthrough fine with more then 4G RAM
with traditional qemu, xen's qemu  upstream does only work with memory
< 4G.


2013/3/5 Pasi Kärkkäinen <pasik@xxxxxx>:
> 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..
>
>> 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!
>
>
> -- 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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