Re: [Xen-devel] pciback bug "secondary bus reset failed"

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Mon, May 24, 2010 at 04:53:01PM +0100, Alex Zeffertt wrote:
> Hi,
>
> I'm trying to passthrough a PCI network card to a domU guest, but I'm 
> hitting a bug that prevents the IRQ being unbound from dom0.
>
> Here are the steps I am taking:
>
>  * configure Xen to pass $pci (0000:06:00.0) through to guest VM
>  * unbind from current driver in dom0 and rebind to pciback:
>
>      echo -n $pci > /sys/bus/pci/devices/$pci/driver/unbind
>      modprobe pciback
>      echo -n $pci > /sys/bus/pci/drivers/pciback/new_slot
>      echo -n $pci > /sys/bus/pci/drivers/pciback/bind
>
>  * start guest VM
>
> I then get the following on the dom0 console
>
>   pciback 0000:06:00.0: secondary bus reset failed for device - all functions 
> \
>   need to be co-assigned - err: 6
>   pciback 0000:06:00.0: FLR functionality not supported; attempts to use \
>   secondary bus reset unsuccessful;
>   pciback 0000:06:00.0: FLR not performed for device
>

Please check this wiki page:
http://wiki.xensource.com/xenwiki/XenPCIpassthrough

It has a chapter about the "all functions need to be co-assigned" error..

-- Pasi

> I don't understand the above, but the upshot is that pirq_guest_unbind() 
> does not get called.  Later when the guest does an "ifconfig up" the IRQ 
> gets sent to dom0 instead of the domU, and this causes the following to 
> appear on the dom0 console:
>
>   irq 21: nobody cared (try booting with the "irqpoll" option)
>   Pid: 0, comm: swapper Tainted: G          
> 2.6.27.42-0.1.1.xs5.6.0.44.111158xen
>    #1
>    [<c0154517>] __report_bad_irq+0x27/0x90
>    [<c015487c>] note_interrupt+0x2fc/0x330
>    [<f009e92d>] ? usb_hcd_irq+0x4d/0xe0 [usbcore]
>    [<c0153951>] ? handle_IRQ_event+0x31/0x90
>    [<c0155204>] handle_level_irq+0xe4/0x110
>    [<c0107733>] do_IRQ+0x43/0x90
>
> I have ioapic_ack=old on the Xen command line.  This causes Xen to EOI 
> the interrupt straight away instead of waiting for a guest to EOI and 
> forwarding that on to the IO APIC.  If I remove this then since no guest 
> handles the interrupt, all lower priority IRQs get blocked forever and I 
> lose access to my hard disk!
>
> Any help would be much appreciated.
>
> Regards,
>
> Alex Zeffertt
>
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