Looking for information on xen bus

Looking for information on xen bus

[Parag Chakraborty]

[-- Attachment #1.1: Type: text/plain, Size: 524 bytes --]

Hi,

 

This is my first post to the xen dev forums. I am new to the linux world and
I am looking for some documentation or information on xen bus. If this is
not the right mailing list, can someone point me to the right one?

 

I am trying to build something that needs a communication channel between 2
domU partitions.

 

Does xen bus support communication between domUs or does it only support
communication between dom0 and domU?

Are there any windows implementation for xenbus on the domU side?

 

Thanks,

Parag


[-- Attachment #1.2: Type: text/html, Size: 2518 bytes --]

[-- Attachment #2: Type: text/plain, Size: 138 bytes --]

_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xensource.com
http://lists.xensource.com/xen-devel

Re: Looking for information on xen bus

[Andy Grover]

On Mon, 2007-12-17 at 14:25 -0800, Parag Chakraborty wrote:
> I am trying to build something that needs a communication channel
> between 2 domU partitions.
> Does xen bus support communication between domUs or does it only
> support communication between dom0 and domU?

Well according to my copy of "The Definitive Guide to the Xen
Hypervisor", xenbus is "an informal protocol built on top of the
xenstore, which provides a way of enumerating the (virtual) devices
available to a given domain, and connecting to them". So it's really for
setup info, not inter-dom communication.

You probably want your domUs to share pages. One of your domUs can
advertise where the page it has shared is (grant ref#, domid) via xenbus
and then the other domU can read xenbus to get the gref and domid, and
map that page.

> Are there any windows implementation for xenbus on the domU side?

Yes, check out http://xenbits.xensource.com/ext/win-pvdrivers.hg . For
the moment you'll have to compile it yourself.

Regards -- Andy

Re: Looking for information on xen bus

[Mark Williamson]

> On Mon, 2007-12-17 at 14:25 -0800, Parag Chakraborty wrote:
> > I am trying to build something that needs a communication channel
> > between 2 domU partitions.
> > Does xen bus support communication between domUs or does it only
> > support communication between dom0 and domU?
>
> Well according to my copy of "The Definitive Guide to the Xen
> Hypervisor", xenbus is "an informal protocol built on top of the
> xenstore, which provides a way of enumerating the (virtual) devices
> available to a given domain, and connecting to them". So it's really for
> setup info, not inter-dom communication.
>
> You probably want your domUs to share pages. One of your domUs can
> advertise where the page it has shared is (grant ref#, domid) via xenbus
> and then the other domU can read xenbus to get the gref and domid, and
> map that page.

Earlier versions of Xen don't allow domUs to share pages directly using grant 
tables.  I think in more recent versions of Xen this is possible, although 
the initial support was buggy.  The code in xen-unstable / Xen 3.2 probably 
does this all right, I think.  I'm not sure off the top of my head what the 
status was for previous versions.

Parag: like Andy says, XenBus is basically just a mechanism for determining 
what virtual devices you have got and for doing the "handshaking" required to 
establish shared memory and event channels.  The bulk of the work of a PV 
virtual device is then done using this shared memory and event channels.

Xenbus is "control plane", and the shared memory and event channels are 
the "fast path" which handles the actual IO.

Cheers,
Mark

> > Are there any windows implementation for xenbus on the domU side?
>
> Yes, check out http://xenbits.xensource.com/ext/win-pvdrivers.hg . For
> the moment you'll have to compile it yourself.
>
> Regards -- Andy
>
>
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xensource.com
> http://lists.xensource.com/xen-devel



-- 
Dave: Just a question. What use is a unicyle with no seat?  And no pedals!
Mark: To answer a question with a question: What use is a skateboard?
Dave: Skateboards have wheels.
Mark: My wheel has a wheel!