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 17:47 +0000, Stefan Bader wrote:
> On 01.12.2011 17:03, Ian Campbell wrote:
> > On Thu, 2011-12-01 at 15:09 +0000, 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.
> > 
> > Which toolstack are you using?
> > 
> xm (xl with the same config seems to work)

That's good. xm is deprecated and this seems to be a known issue with
xend. There is a workaround which is to not specify type=.

> 
> > The weird thing is that, at least with xl, type=ioemu is the default for
> > an HVM guest.
> > 
> > What vif related entries do you get in xenstore, both front and backend?
> > 
> output of xenstore-ls attached (hopefully contains all info)

FWIW the xend frontend dir looks more empty than I would have expected.
However given the above I don't think we want to spend time figuring out
why.

Ian.

> 
> > Also what does your qemu-dm command line end up looking like?
> > 
> also in the attached file.
> 
> >> 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.
> > 
> > That is certainly the expectation.
> > 
> >> Is that something that can be seen with newer Xen versions, too (I am 
> >> using 4.1.1)?
> > 
> > I appear to have some other problem with xen-unstable at the moment.
> > I've never noticed a problem in that past, although I don't habitually
> > use type=XXX at all in my vif configuration.
> > 
> > Ian.
> > 
> >> -Stefan
> > 
> > 
> 



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