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

[Pasi Kärkkäinen]

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