Re: pciback bug "secondary bus reset failed"

[Weidong Han <weidong.han@intel.com>]

Alex Zeffertt wrote:
> 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? 
>   
No. Dom0 still can access the card. Dom0 just doesn't perform FLR on it 
to avoid your issue.
> 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?
>   
Yes. FLR is required by pci passthrough. your NIC only can be 
co-assigned (#1). #2 is just a temporary workaround for your try.

Regards,
Weidong
> Thanks again,
>
> Alex
>
>
>
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