Xen devel - Nov 2007 - Equivalent of XenBus for fully-virtualized Xen

Hello,

http://wiki.xensource.com/xenwiki/XenBusDriver?highlight=%28xenbus%29 
says that "XenBus provides a bus abstraction for paravirtualized drivers 
to communicate between domains. In practice, the bus is used for 
configuration negotiation, leaving most data transfer to be done via 
page flipping."

What is the equivalent mechanism for fully-virtualized drivers in Xen 
(HVM running on VT-capable machine)?
-- 
Kaushik Bhandankar


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> http://wiki.xensource.com/xenwiki/XenBusDriver?highlight=%28xenbus%29
> says that "XenBus provides a bus abstraction for paravirtualized
drivers
> to communicate between domains. In practice, the bus is used for
> configuration negotiation, leaving most data transfer to be done via
> page flipping."
>
> What is the equivalent mechanism for fully-virtualized drivers in Xen
> (HVM running on VT-capable machine)?
An interface to the same Xenbus facilities is provided to an HVM guest via 
the "Xen platform device" - a fake PCI device which allows a guest to 
communicate with Xen platform services as if it were a real device.

The PV drivers for HVM provide a driver that can talk to this platform device; 
the block and net paravirt drivers then use this to access the Xenbus 
functionality that they need.

Cheers,
Mark

-- 
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!

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My HVM guest is using 2.6.16.13 and my Dom0 is using 2.6.18.8 (uname -r)

So, I downloaded the kernel source for 2.6.16.13 from kernel.org and 
installed it under /usr/src in Dom0 (untar followed by make mrproper)

Then I did

    # cd xen-unstable.hg/unmodified_drivers/linux-2.6
    # sh mkbuildtree
    # make -C /usr/src/linux-2.6.16.13 M=$PWD modules

At this point, I get a bunch of warnings and errors......I am attaching 
the log produced by make...

-Kaushik

Mark Williamson wrote:
>> thanks..... I stumbled upon
>>
http://lists.xensource.com/archives/html/xen-ia64-devel/2006-10/msg00177.ht
>> ml which talks about PV-on-HVM but I am using a VBD image for the HVM
guest
>> and not really sure if I should proceed as directed.
> 
> I''m not sure I follow...  Is your problem with how to transfer the
PV drivers
> into the guest?  The lomount tool should mount any image (with the
exception
> of qcow) alright and then you can copy the drivers in.  The instructions in
> the mail only really make sense if you''re running the same
compiler and
> kernel (i.e. the same distro) in guest and host though.  If not, you may as
> well build and install the new drivers *from inside the guest* rather than 
> building in dom0 and copying them in.
> 
> 
>> Any pointers are appreciated.
> 
> Does that help?
> 
> Cheers,
> Mark
> 
>> -Kaushik
>>
>> Mark Williamson wrote:
>>>>
http://wiki.xensource.com/xenwiki/XenBusDriver?highlight=%28xenbus%29
>>>> says that "XenBus provides a bus abstraction for
paravirtualized drivers
>>>> to communicate between domains. In practice, the bus is used
for
>>>> configuration negotiation, leaving most data transfer to be
done via
>>>> page flipping."
>>>>
>>>> What is the equivalent mechanism for fully-virtualized drivers
in Xen
>>>> (HVM running on VT-capable machine)?
>>> An interface to the same Xenbus facilities is provided to an HVM
guest
>>> via the "Xen platform device" - a fake PCI device which
allows a guest to
>>> communicate with Xen platform services as if it were a real device.
>>>
>>> The PV drivers for HVM provide a driver that can talk to this
platform
>>> device; the block and net paravirt drivers then use this to access
the
>>> Xenbus functionality that they need.
>>>
>>> Cheers,
>>> Mark
> 
> 
> 

-- 
Kaushik Bhandankar

Graduate Student
College of Computing
Georgia Tech
206.949.4189
www.cc.gatech.edu/~kaushikb


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