Re: [Xen-devel] [PATCH v6 10/13] libxl: set nic type to VIF by default

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Tue, 2012-06-26 at 17:58 +0100, Pasi KÃrkkÃinen wrote:
> On Tue, Jun 26, 2012 at 05:20:35PM +0100, Roger Pau Monne wrote:
> > Ian Jackson wrote:
> > >Roger Pau Monne writes ("[PATCH v6 10/13] libxl: set nic type to VIF by 
> > >default"):
> > >>Set the default value for nic interfaces to VIF, since it used to be
> > >>IOEMU, even for PV guests.
> > >
> > >If your renaming of IOEMU to VIF_IOEMU is correct, does this not stop
> > >HVM guests getting emulated network interfaces by default ?
> > 
> > Yes, if you want emulated interfaces with HVM guests you should use
> > 'type=ioemu', that's how it has always been right?
> > 
> 
> With Xen 4.1 you don't have to use "type=ioemu". Emulated interfaces seem to 
> work OK without "type=ioemu".
> (at least with xm/xend). And if you actually do add "type=ioemu" it will 
> break PVHVM for Linux guests..
> 
> Quote from: http://wiki.xen.org/wiki/XenLinuxPVonHVMdrivers
> 
> "NOTE! If you have "type=ioemu" specified for the "vif"-line, PVHVM
> drivers WILL NOT work! Don't specify "type" parameter for the vif.
> (with type=ioemu the pvhvm nic in the VM will have mac address full of
> zeroes - and thus won't work!). "

mac=00:00:00:00:00 is certainly a bug, if (lib)xl behaves this way too
then we should fix it.

But surely type=ioemu is supposed to mean "only emulated"? In which case
the actual xend bug is that it created a PV VIF at all.

What are the options here? I think they are, with their (lib)xl
behaviour:

                PV                              HVM
type=ioemu      meaningless / an error          emulated device + paravirt VIF*
type=vif        paravirt VIF device*&           paravirt VIF device only&

Where * == current lib(xl) default and & == proposed default after this change.
and:
        type=ioemu =>   LIBXL_NIC_TYPE_IOEMU to be renamed 
LIBXL_NIC_TYPE_VIF_IOEMU.
        type=vif =>     LIBXL_NIV_TYPE_VIF, no renaming proposed.
        
But if my table is correct then LIBXL_NIC_TYPE_VIF_IOEMU is the right
default and shouldn't be changed. Roger can you either confirm or
correct my table.

Ian.


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