Re: [Xen-devel] Re: follow up to a pciback "pv pci-passthrough co-assigned problem"

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Tue, Jan 26, 2010 at 09:42:00AM +0800, Weidong Han wrote:
> 0bo0 wrote:
>> hi,
>>
>> On Sun, Jan 24, 2010 at 5:44 PM, Weidong Han <weidong.han@xxxxxxxxx> wrote:
>>   
>>> I think this is not a bug. pls note ...
>>>     
>>
>> (snip)
>>
>> Ack'd, even if the limitations are not fully understood:-/
>>
>>   
>>> or you
>>> can set "pci-passthrough-strict-check no" in /etc/xen/xend-config.sxp and
>>> restart xend to loose the check in xend, but in this way you should be aware
>>> of potential issues (e.g. assigned device doesn't work).
>>>     
>>
>> sure.  would it not be reasonable to have a similar config-file option
>> in xen 3.x -- with similar warnings etc -- as is done in 4.x? if all
>> that's required for a workaround is a patch similar to that above ...
>>
>> thanks
>>   
> The option was introduced by changeset 20179. It's small. It can be back  
> ported to Xen 3.x if need.
>

It would be good to backport this.

The point here is, I think, that before the VT-d stuff you could passthrough
for example each port from a dual-port NIC to different PV guests, even
if it was not the recommended way.

Now at some point it stopped working for many people, and Xen started 
complaining
that the devices need to be passed to the same guest.

I know some people are also using another port from a dual-port NIC in the 
dom0, 
and another port passthroughed to a PV guest. And they've been doing this for a 
long time.

-- Pasi


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