Re: [Xen-devel] [PATCH 11/13] libxl: set nic type to VIF by default

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

Ian Campbell wrote:
> On Tue, 2012-05-29 at 15:40 +0100, Ian Jackson wrote:
> > Roger Pau Monne writes ("Re: [PATCH 11/13] libxl: set nic type to VIF by 
> > default"):
> > > Ian Jackson wrote:
> > > > Roger Pau Monne writes ("[PATCH 11/13] libxl: set nic type to VIF by default"):
> > > > > -        nic->nictype = LIBXL_NIC_TYPE_IOEMU;
> > > > > +        nic->nictype = LIBXL_NIC_TYPE_VIF;
> > > > But doesn't this set the default type to VIF even for HVM guests ?
> > > Shouldn't HVM guests use the "ioemu" parameter if they want an emulated
> > > card? If no parameter is provided then the default type should be VIF,
> > > because there's no other way to specifically set the type to VIF.
> > Sorry.  I seem to have failed to reply to this.
> >
> > I'm a bit confused about all this, I confess.  What does xend do ?
> >
> > ATM it seems that this change would mean that a guest config file
> > specified in the most obvious way wouldn't get an emulated nic at
> > all.  That can't be right, can it ?
> It's confusingly named.
>
> IOEMU ->  emulated only on HVM, meaningless on PV.
My understanding was that IOEMU meant both TAP and PV, and was only 
valid for HVM guests, and VIF meant PV only and was valid for both 
domain types?
I don't think this is right, this will mean VIF has a different meaning 
depending on the type of domain, which is quite annoying.
If this is right, I have to change my hotplug patches, but this will be 
a mess, because I have no way to tell if a domain is PV or HVM when 
plugging in the devices, so if VIF is passed for both PV or PV+TAP I 
will have no way of knowing that.
Should we create three different nic types? VIF (PV), IOEMU (TAP), 
HYBRID (PV+TAP)?
> VIF   ->  both emulated and PV (on HVM) or just PV (on PV)
>
> So a default of "VIF" is what you normally want.
>
> Ian.

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