[CentOS-virt] CentOS 6 Xen virt* issues

Johnny Hughes

johnny at centos.org
Tue Sep 29 15:00:01 UTC 2015

On 09/29/2015 07:55 AM, Pasi Kärkkäinen wrote:
> On Tue, Sep 29, 2015 at 12:37:25PM +0100, George Dunlap wrote:
>> On Sat, Sep 26, 2015 at 9:29 PM, Pasi Kärkkäinen <pasik at iki.fi> wrote:
>>> On Sat, Sep 26, 2015 at 09:04:23PM +0300, Pasi Kärkkäinen wrote:
>>>> Hello,
>>>> I just upgraded some of my el6xen boxes to latest CentOS 6.7, Xen 4.4.3 and dom0 3.18.17 rpms, and noticed these new problems:
>>> And third issue aswell:
>>> 3) Creating an HVM guest using virt-manager with file-based storage uses loopback-mount, not blktap
>>> When I manually create a new Xen HVM guest using virt-manager, and choose file-based image for storage of the VM, it seems to be set up to use file: backend/driver with loopback-mounted image file:
>>>     <disk type='file' device='disk'>
>>>       <driver name='file'/>
>>>       <source file='/var/lib/libvirt/images/testvm2.img'/>
>>>       <backingStore/>
>>>       <target dev='hda' bus='ide'/>
>>>     </disk>
>>> # losetup -a
>>> /dev/loop0: [fd00]:1709109 (/var/lib/libvirt/images/testvm2.img)
>>> With earlier versions of rpms similar setup used blktap2 backend.. (and yes, I do have blktap module loaded in dom0 kernel).
>> I remember having to patch some dependency of virt-manager to give it
>> the correct default driver name (something like, it got 'tap' but
>> needed to be 'tap2').  In all likelihood, someone has sussed that
>> 'tap' doesn't work and just replaced it with 'file'.  Actually, it's
>> fairly likely if they've updated stuff in CentOS that you're not
>> getting the re-build virt-manager stuff either -- I may have to respin
>> that one as well.
> I think it's specified at least in python-virtinst. See these emails from a few years back about the tap/tap2-issue:
> https://www.redhat.com/archives/virt-tools-list/2013-June/msg00037.html
> https://www.redhat.com/archives/virt-tools-list/2013-June/msg00039.html

This is indeed where it was patched before (as a stand alone program) ..
have they now rolled that into virt-manager?

>> While we're here, could you give me a couple of virt-install and
>> virt-viewer "smoketest" commands that I could add to my automated test
>> scripts?  ATM I'm testing libvirt by using virsh to import an xl .cfg
>> file, but it would be better to have something that created the config
>> end-to-end.  Using virt-manager directly is probably more work than
>> I'm up for in most cases, but hopefully if I can test the things it
>> depends on I can notice this sort of breakage.
> The problem with virt-viewer issue is that it gives the "error popup" in the GUI,
> so there's no way to figure out it didn't work without looking at the GUI and interacting with the gui..
> Not easy to script/automate..
>> Thanks,
>>  -George
> -- Pasi

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