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

[Stefan Bader <stefan.bader@xxxxxxxxxxxxx>]

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)

> 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)

> 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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