Does it support to specify virtual function in guest for assigned device

Does it support to specify virtual function in guest for assigned device

[Han, Weidong]

Hi Simon,

You did lots of work on multiple functions passthrough. We can specify virtual slot for assigned device like pci=[ '01:00.0@5' ]. Does it support to specify virtual function in guest for assigned device? For example, I want to specify virtual bdf 00:05.1 for device 01:00.1. Thanks.

Regards,
Weidong

Re: Does it support to specify virtual function in guest for assigned device

[Simon Horman]

On Tue, Sep 08, 2009 at 04:10:57PM +0800, Han, Weidong wrote:
> Hi Simon,
> 
> You did lots of work on multiple functions passthrough. We can specify
> virtual slot for assigned device like pci=[ '01:00.0@5' ]. Does it
> support to specify virtual function in guest for assigned device? For
> example, I want to specify virtual bdf 00:05.1 for device 01:00.1.

Hi Weidong,

Yes, as of changeset "xend: pass-through: Extend multi-function mapping"
(20012:3242351f9c67) is is possible to specify the virtual function.

However, this is only possible for multi-function pass-through.
When only a single function is passed through the virtual function
will always be zero, because PCI devices must always have function 0
present.

So the closest that you could do when passing through 01:00.1 is to get
virtual function 00:05.0 by specifying '01:00.1@5'.

If you passed through another function of 01:00 at the same time as 01:00.1,
say 01:00.0, then you could explicitly choose to have 01:00.1
assigned to 00:05.1 and 01:00.0 assigned to 00:05.0 using '00:05.0=0,1=1@5'.

Actually that would be the default as it is just an identity mapping,
so the same result would be achieved by '00:05.0,1@5'. A more interesting
case would be to reverse the mapping so 00:05.0 -> 01:00.1 and
00:05.1 -> 00:05.0, which could be achieved using '00:05.0=1,1=0@5'.

RE: Does it support to specify virtual function in guest for assigned device

[Han, Weidong]

Simon Horman wrote:
> On Tue, Sep 08, 2009 at 04:10:57PM +0800, Han, Weidong wrote:
>> Hi Simon,
>> 
>> You did lots of work on multiple functions passthrough. We can
>> specify virtual slot for assigned device like pci=[ '01:00.0@5' ].
>> Does it support to specify virtual function in guest for assigned
>> device? For example, I want to specify virtual bdf 00:05.1 for
>> device 01:00.1. 
> 
> Hi Weidong,
> 
> Yes, as of changeset "xend: pass-through: Extend multi-function
> mapping" (20012:3242351f9c67) is is possible to specify the virtual
> function. 
> 
> However, this is only possible for multi-function pass-through.
> When only a single function is passed through the virtual function
> will always be zero, because PCI devices must always have function 0
> present.
> 
> So the closest that you could do when passing through 01:00.1 is to
> get virtual function 00:05.0 by specifying '01:00.1@5'.
> 
> If you passed through another function of 01:00 at the same time as
> 01:00.1, say 01:00.0, then you could explicitly choose to have 01:00.1
> assigned to 00:05.1 and 01:00.0 assigned to 00:05.0 using
> '00:05.0=0,1=1@5'. 
> 
> Actually that would be the default as it is just an identity mapping,
> so the same result would be achieved by '00:05.0,1@5'. A more
> interesting case would be to reverse the mapping so 00:05.0 ->
> 01:00.1 and 00:05.1 -> 00:05.0, which could be achieved using
> '00:05.0=1,1=0@5'. 

Hi Simon,

Thanks for your detailed explanation. I need the option '00:05.0=0,1=1@5'. BTW, did you add these option explanation to any document? It is helpful if you do it.

Regards,
Weidong

Re: Does it support to specify virtual function in guest for assigned device

[Simon Horman]

On Wed, Sep 09, 2009 at 06:52:05AM +0800, Han, Weidong wrote:
> 
> Hi Simon,
> 
> Thanks for your detailed explanation. I need the option '00:05.0=0,1=1@5'. BTW, did you add these option explanation to any document? It is helpful if you do it.

Hi Weidong,

I have put some details about this up at:
http://wiki.xensource.com/xenwiki/BDFNotation#multi-function

Which is referenced from:
http://wiki.xensource.com/xenwiki/VTdHowTo

RE: Does it support to specify virtual function in guest for assigned device

[Han, Weidong]

Simon Horman wrote:
> On Wed, Sep 09, 2009 at 06:52:05AM +0800, Han, Weidong wrote:
>> 
>> Hi Simon,
>> 
>> Thanks for your detailed explanation. I need the option
>> '00:05.0=0,1=1@5'. BTW, did you add these option explanation to any
>> document? It is helpful if you do it.  
> 
> Hi Weidong,
> 
> I have put some details about this up at:
> http://wiki.xensource.com/xenwiki/BDFNotation#multi-function
> 
> Which is referenced from:
> http://wiki.xensource.com/xenwiki/VTdHowTo

It's good. Thanks.

Regards,
Weidong