Re: pciback bug "secondary bus reset failed"

[Alex Zeffertt <alex.zeffertt@eu.citrix.com>]

Pasi Kärkkäinen wrote:
> 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

Hi Pasi,

Thanks for your reply.  I think I understand what is happening now.  My card is 
too old to have the Function Level Reset functionality.  This leaves the 
following options:


  1. Assign all the cards that share the PCI bus (0000:06) to the same guest. 
This enables the FLR functionality to be replaced by the bridge's "Secondary Bus 
Reset" functionality

  - or -

  2. Apply the patch referred to on 
http://wiki.xensource.com/xenwiki/XenPCIpassthrough to bypass the FLR


If I can't do number #1 because some cards are in use by dom0 then I guess #2 is 
the only option.  But does #2 require that dom0 has never accessed the card? 
Also, what if you reboot the domU - does the fact that you can't do an FLR on 
the card mean that there will be unpredictable results the 2nd time domU tries 
to initialise it?

Thanks again,

Alex