Re: [Xen-devel] Xen 4.1.2 PVHVM guest with Linux 3.1.0 network problem, empty MAC address (all zeroes)

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Mon, Oct 31, 2011 at 10:51:34PM +0200, Pasi Kärkkäinen wrote:
> On Mon, Oct 31, 2011 at 10:13:36PM +0200, Pasi Kärkkäinen wrote:
> > Hello,
> > 
> > While testing Fedora 16 Xen PVHVM guests I noticed the following problem:
> > 
> > When starting F16 PVHVM guest I can see the vifX.0 and tapX.0 interfaces 
> > appear on dom0, 
> > but after the guest kernel (Linux 3.1.0) starts and loads PVHVM drivers the 
> > vif/tap interfaces disappear from dom0.. 
> > so the bridge in dom0 doesn't have any vifs/taps connected to it anymore.
> > 
> > Has anyone seen that behaviour? 
> > 
> > I bet that's also the reason why eth0 inside the PVHVM guest 
> > has a MAC address with only zeroes in it: 00:00:00:00:00:00.
> > 
> > If I disable PVHVM with "xen_platform_pci=0" in the domain cfgfile
> > then network for the guest works OK using the qemu-dm emulated nic.
> > 
> > PVHVM guest cfgfile:
> > 
> 
> <snip>
> 
> > 
> > Some output from inside the PVHVM guest:
> > 
> > # ifconfig eth0
> > eth0      Link encap:Ethernet  HWaddr 00:00:00:00:00:00
> >           BROADCAST MULTICAST  MTU:1500  Metric:1
> >           RX packets:0 errors:0 dropped:0 overruns:0 frame:0
> >           TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
> >           collisions:0 txqueuelen:1000
> >           RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)
> > 
> 
> <snip>
> 
> > 
> > Full PVHVM guest kernel (Linux 3.1.0) dmesg attached to this email.
> > Some parts of the guest dmesg here:
> > 
> > $ egrep -i 'xen|vif' xen-4.1.2-f16pvhvm-linux-3.1.0-dmesg.txt
> > 
> 
> <snip>
> 
> > 
> > dom0 kernel (Linux 3.1.0 aswell) messages:
> > 
> 
> <snip>
> 
> > 
> > 
> > "xm log" doesn't have any errors.
> > Any ideas how to fix this? Why do the vif/tap devices disappear from dom0?
> > 
> 
> Well.. it was actually as simple as removing "type=ioemu" from the vif line.
> Working vif-example for Xen PVHVM Linux guest VM:
> 
> vif = [ 'mac=00:16:5f:03:01:15, bridge=virbr0, model=e1000' ]
> 
> So uhm.. when enabling PVHVM there's no need to modify the disk line, 
> but you need to modify the vif-line.. is that like it should be ?
> 

It seems "type=ioemu" is not required for anything.. 
not even for normal HVM emulated nics.

So this works for both normal HVM and PVHVM:
vif = [ 'mac=00:16:5f:03:01:15, bridge=virbr0, model=e1000' ]

And control the HVM/PVHVM mode with:
        xen_platform_pci=1
or
        xen_platform_pci=0



-- Pasi


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