A query on frame buffers

[Prasad Joshi]

On Fri, Jan 7, 2011 at 7:24 PM, Konrad Rzeszutek Wilk
<konrad.wilk at oracle.com> wrote:
> On Fri, Jan 07, 2011 at 05:47:59PM +0000, Prasad Joshi wrote:
>> 2011/1/7 Konrad Rzeszutek Wilk <konrad.wilk at oracle.com>:
>> >> > The errors
>> >> >
>> >> > [    3.778476] [drm:r100_ring_test] *ERROR* radeon: ring test failed
>> >> > (sracth(0x15E4)=0xCAFEDEAD)
>> >> > [    3.781010] [drm:r100_cp_init] *ERROR* radeon: cp isn't working (-22).
>> >> > [    3.782542] radeon 0000:00:04.0: failled initializing CP (-22).
>> >> > [    3.784006] radeon 0000:00:04.0: Disabling GPU acceleration
>> >> >
>> >> > Seem to be disabling GPU functionality. For now, I am interested in
>> >> > Graphics functionality of the ATI card and not GPGPU functionality.
>> >> >
>> >> > I will appreciate if you can help me with some information on solving
>> >> > this problem. Let me know if I should be asking this question on
>> >> > another forum. Please keep me in CC.
>> >>
>> >> Looks like dri-devel material, added to CC.
>> >>
>> >> As a first guess, maybe the system memory pages accessed by the GPU GART
>> >> aren't the same ones intended for this by the VM.
>> >
>> > I actually have patches for that (sorry for the late reply).
>> >
>> > Try:
>> > git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen.git devel/ttm.pci-api.v3
>> >
>> > But I am not sure if they would make any difference here. You said
>> > you are using KVM-QEMU - you must also be using an IOMMU? Does the IOMMU
>> > give you any errors?
>> >
>>
>> Yes I want to pass-through the ATI Radeon card to VM in KVM. I have
>> enabled the IOMMU support and it works perfectly alright. I tried
>> passing through a network card it worked.
>>
>> Should I try the patch you suggested?
>
> Go for it. I am still at lost why you would see those errors unless..

Tried your patches on Guest machine, it did not help. I am attaching
the messages from guest machine.

> well, what is the DMA code that gets turned on when you run your guest?

Looking into the qemu-kvm code to find more information about DMA.

> What do you see for 'PCI-DMA' ?

> Is it bounce buffer or swiotlb?

It is the default configuration. I did not pass swiotlb parameter on
kernel boot line.

The host kernel is booted with iommu=1.

> How much memory do you pass to the guest? less than 4GB?

root at prasad-kvm:~/VMDisks# qemu-system-x86_64 -hda
Ubuntu-10.10-amd64.img -m 1024M -device pci-assign,host=02:00.0

I am passing 1GB memory to the guest machine.

>

I have 2 graphics cards (Nvidia and ATI) attached to my system. The
Nvidia graphics card is used by host machine and I am trying to assign
the ATI graphics card to the Guest machine.

When I unbind the ATI graphics card from the host machine I see these
messages on the host machine
Jan 10 11:59:15 prasad-kvm kernel: [ 3396.912767] pci-stub: invalid id string ""
Jan 10 11:59:59 prasad-kvm kernel: [ 3441.180601] pci-stub
0000:02:00.1: claimed by stub
Jan 10 12:00:08 prasad-kvm kernel: [ 3449.901870] [drm] radeon:
finishing device.
Jan 10 12:00:08 prasad-kvm kernel: [ 3449.902161] [drm] radeon: cp finalized
Jan 10 12:00:08 prasad-kvm kernel: [ 3449.903435] radeon 0000:02:00.0:
ffff88022ae3d200 unpin not necessary
Jan 10 12:00:08 prasad-kvm kernel: [ 3449.903490] [drm] radeon: ttm finalized
Jan 10 12:00:08 prasad-kvm kernel: [ 3449.903551] vga_switcheroo: disabled

Thanks a lot for helping me out.

Thanks and Regards,
Prasad
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