Re: [Xen-devel] Xen 4.x / Linux 3.x (dom0 and HVM domU) and NIC handling

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Thu, 2011-12-01 at 18:09 +0000, Pasi KÃrkkÃinen wrote:
> On Thu, Dec 01, 2011 at 04:09:38PM +0100, Stefan Bader wrote:
> > Moving to public discussion...
> > 
> > This was found with Xen hypervisor version supporting device unplugging and 
> > the
> > domU kernel having net-/blkfront and pci platform built-in (or as module).
> > 
> > The block device is defined as hda and the NIC type=ioemu (so theoretically
> > guests without pv support would work, too).
> > 
> > Since both drivers are present, the kernel tries to unplug the emulated 
> > devices
> > and succeeds. The blkfront driver detects the xvda device available in 
> > parallel
> > and is working ok.
> > 
> > However the network interface does not work. There are entries present under
> > sysfs for the xenbus but trying to bring it up fails with errors. And also 
> > there
> > seems to be no mac address set (all zeros in sysfs).
> > When the type=ioemu is removed in the configuration, this works.
> > 
> > I have not much more debugging information beyond that, yet. But it sounds 
> > a bit
> > like NICs should behave the same as block devices. So if there is an 
> > emulated
> > device defined there will be an alternate paravirt interface for it and 
> > after
> > unplugging the emulated ones we end up with the pv ones.
> > Is that something that can be seen with newer Xen versions, too (I am using 
> > 4.1.1)?
> > 
> 
> Hey,
> 
> Have you seen?: 
> http://wiki.xen.org/xenwiki/XenLinuxPVonHVMdrivers

I was about to say "Please use the new wiki URLs where possible" but the
section you refer to seems to be missing in the new wiki!

http://wiki.xen.org/wiki/XenLinuxPVonHVMdrivers

It is there in
http://wiki.xen.org/old-wiki-converted/XenLinuxPVonHVMdrivers.txt but
not in the first revision in the new wiki. Lars, do you know what
happened here?

> 
> Especially the following note:
> "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!)."
> 
> "type=ioemu" is not needed, at least with xm/xend toolstack both HVM and 
> PVHVM guests work OK without it.
> 
> -- Pasi
> 



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