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RE: [Xen-devel] HVM guest sees two NICs even though just one vif config

To: Ky Srinivasan <ksrinivasan@xxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: RE: [Xen-devel] HVM guest sees two NICs even though just one vif configured
From: "Fischer, Anna" <anna.fischer@xxxxxx>
Date: Thu, 6 Aug 2009 15:27:25 +0000
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Thread-topic: [Xen-devel] HVM guest sees two NICs even though just one vif configured
> Subject: Re: [Xen-devel] HVM guest sees two NICs even though just one
> vif configured
> >>> On 8/6/2009 at  5:32 AM, in message
> <0199E0D51A61344794750DC57738F58E6D6A501125@xxxxxxxxxxxxxxxxxxxxxxxxxxx
> .net>,
> "Fischer, Anna" <anna.fischer@xxxxxx> wrote:
> > I am running SLES10 with Xen 3.2 and I have configured an HVM guest.
> What version of sles10 are you installing? In sles10 sp3, if you
> install with our tools you automatically get PV drivers (both NIC and
> disk) enabled. Our tools will generate the appropriate config file
> (with type=netfront) and appropriate kernel boot option to disable
> probing of the hard disk. Prior to sles10 SP3, one had to manually
> enable PV drivers after installing using the emulated devices.

But how can the tools in Dom0 know whether your guest runs PV drivers or not? 
This assumes that your guest runs SLES10 as well and has your PV driver 
packages installed. Only then you can set type=netfront. Otherwise, if you set 
type=netfront, and your guest does not have PV drivers installed, then your 
guest will not have any networking device that works...

You are assuming that you know what the guest has installed, only then you can 
set the type=[netfront|ioemu] correctly. In my case though, I don't know what 
the guest runs, so I would need it to be detected automatically. It works to 
some extend right now, and it can switch between emulated NIC and PV NIC 
automatically, if the guest does it properly. However, if the guest does not do 
it right (on purpose or by mistake), then I suddenly have a guest with two 
active NICs attached.


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