Xen devel - Jun 2013 - libvirt and virt-manager default blktap driver name for file images, tap vs tap2?

Hello,

Does anyone know where/how to set the default libvirt blktap "driver
name" for disk image files?

If I have "blktap" module loaded in dom0 kernel, and I do this:

virt-install -d -n blktaptest01 -r 2048 --vcpus=2 --disk
/var/lib/libvirt/images/blktaptest01.img,size=8 --vnc -p -l
"http://ftp.funet.fi/pub/mirrors/centos.org/6.4/os/x86_64"

which results in this generated libvirt xml config for the VM:

    <disk type=''file'' device=''disk''>
      <driver name=''tap'' type=''aio''/>
      <source
file=''/var/lib/libvirt/images/blktaptest01.img''/>
      <target dev=''xvda'' bus=''xen''/>
    </disk>

.. which doesn''t seem to work for me with Xen 4.2.2 using xm/xend, and
libvirt 0.10.x.

The problem is there''s no tapdisk process started in dom0, and the
block device cannot be
initialized or accessed inside the VM. I have the same problem with
virt-manager,
using the "new VM" wizard with disk image files.

The correct "driver name" for libvirt is "tap2", which works
for me,
so I need to manually edit the libvirt xml config to make the VM boot/work.

This matches xm/xend behaviour with text config files for VMs. 
I need to use tap2 there aswell on the disk = [] line.

Where should I choose/set/patch the default libvirt driver name? Is that in
libvirt sources,
or in virt-install/virt-manager ? I tried reading the libvirt "xen"
driver source,
but I couldn''t find any "default" setting there.. 

Thanks,

-- Pasi

Pasi Kärkkäinen wrote:
> Hello,
>
> Does anyone know where/how to set the default libvirt blktap "driver
name" for disk image files?
>
> If I have "blktap" module loaded in dom0 kernel, and I do this:
>
> virt-install -d -n blktaptest01 -r 2048 --vcpus=2 --disk
/var/lib/libvirt/images/blktaptest01.img,size=8 --vnc -p -l
"http://ftp.funet.fi/pub/mirrors/centos.org/6.4/os/x86_64"
>   
Does it work if you specify the driver name in the diskopts?  E.g.

  --disk /var/lib/libvirt/images/blktaptest01.img,size=8,driver_name=tap2

Regards,
Jim
> which results in this generated libvirt xml config for the VM:
>
>     <disk type=''file''
device=''disk''>
>       <driver name=''tap''
type=''aio''/>
>       <source
file=''/var/lib/libvirt/images/blktaptest01.img''/>
>       <target dev=''xvda''
bus=''xen''/>
>     </disk>
>
> .. which doesn''t seem to work for me with Xen 4.2.2 using xm/xend,
and libvirt 0.10.x.
>
> The problem is there''s no tapdisk process started in dom0, and the
block device cannot be
> initialized or accessed inside the VM. I have the same problem with
virt-manager,
> using the "new VM" wizard with disk image files.
>
> The correct "driver name" for libvirt is "tap2", which
works for me,
> so I need to manually edit the libvirt xml config to make the VM boot/work.
>
> This matches xm/xend behaviour with text config files for VMs. 
> I need to use tap2 there aswell on the disk = [] line.
>
> Where should I choose/set/patch the default libvirt driver name? Is that in
libvirt sources,
> or in virt-install/virt-manager ? I tried reading the libvirt
"xen" driver source,
> but I couldn''t find any "default" setting there.. 
>
> Thanks,
>
> -- Pasi
>
>
>

On Thu, Jun 06, 2013 at 12:58:41PM -0600, Jim Fehlig
wrote:
> Pasi Kärkkäinen wrote:
> > Hello,
> >
> > Does anyone know where/how to set the default libvirt blktap
"driver name" for disk image files?
> >
> > If I have "blktap" module loaded in dom0 kernel, and I do
this:
> >
> > virt-install -d -n blktaptest01 -r 2048 --vcpus=2 --disk
/var/lib/libvirt/images/blktaptest01.img,size=8 --vnc -p -l
"http://ftp.funet.fi/pub/mirrors/centos.org/6.4/os/x86_64"
> >   
> 
> Does it work if you specify the driver name in the diskopts?  E.g.
> 
>   --disk /var/lib/libvirt/images/blktaptest01.img,size=8,driver_name=tap2
>
Yep, that works.

I was mostly wondering how to specify/change the *default*,
so that both virt-install and virt-manager work without specifying
driver_name=tap2 ..

Any ideas about that?

Thanks,

-- Pasi

 
> Regards,
> Jim
> 
> > which results in this generated libvirt xml config for the VM:
> >
> >     <disk type=''file''
device=''disk''>
> >       <driver name=''tap''
type=''aio''/>
> >       <source
file=''/var/lib/libvirt/images/blktaptest01.img''/>
> >       <target dev=''xvda''
bus=''xen''/>
> >     </disk>
> >
> > .. which doesn''t seem to work for me with Xen 4.2.2 using
xm/xend, and libvirt 0.10.x.
> >
> > The problem is there''s no tapdisk process started in dom0,
and the block device cannot be
> > initialized or accessed inside the VM. I have the same problem with
virt-manager,
> > using the "new VM" wizard with disk image files.
> >
> > The correct "driver name" for libvirt is "tap2",
which works for me,
> > so I need to manually edit the libvirt xml config to make the VM
boot/work.
> >
> > This matches xm/xend behaviour with text config files for VMs. 
> > I need to use tap2 there aswell on the disk = [] line.
> >
> > Where should I choose/set/patch the default libvirt driver name? Is
that in libvirt sources,
> > or in virt-install/virt-manager ? I tried reading the libvirt
"xen" driver source,
> > but I couldn''t find any "default" setting there.. 
> >
> > Thanks,
> >
> > -- Pasi
> >
> >
> >

Pasi Kärkkäinen wrote:
> On Thu, Jun 06, 2013 at 12:58:41PM -0600, Jim Fehlig wrote:
>   
>> Pasi Kärkkäinen wrote:
>>     
>>> Hello,
>>>
>>> Does anyone know where/how to set the default libvirt blktap
"driver name" for disk image files?
>>>
>>> If I have "blktap" module loaded in dom0 kernel, and I do
this:
>>>
>>> virt-install -d -n blktaptest01 -r 2048 --vcpus=2 --disk
/var/lib/libvirt/images/blktaptest01.img,size=8 --vnc -p -l
"http://ftp.funet.fi/pub/mirrors/centos.org/6.4/os/x86_64"
>>>   
>>>       
>> Does it work if you specify the driver name in the diskopts?  E.g.
>>
>>   --disk
/var/lib/libvirt/images/blktaptest01.img,size=8,driver_name=tap2
>>
>>     
>
> Yep, that works.
>
> I was mostly wondering how to specify/change the *default*,
> so that both virt-install and virt-manager work without specifying
driver_name=tap2 ..
>   
Ahh.
> Any ideas about that?
>   
No, but I''m not that familiar with virt-{install,manager} code.  Seems
like a good question for virt-tools-list@redhat.com.

Regards,
Jim

On Thu, Jun 06, 2013 at 06:41:22PM -0600, Jim Fehlig
wrote:
> Pasi Kärkkäinen wrote:
> > On Thu, Jun 06, 2013 at 12:58:41PM -0600, Jim Fehlig wrote:
> >   
> >> Pasi Kärkkäinen wrote:
> >>     
> >>> Hello,
> >>>
> >>> Does anyone know where/how to set the default libvirt blktap
"driver name" for disk image files?
> >>>
> >>> If I have "blktap" module loaded in dom0 kernel, and
I do this:
> >>>
> >>> virt-install -d -n blktaptest01 -r 2048 --vcpus=2 --disk
/var/lib/libvirt/images/blktaptest01.img,size=8 --vnc -p -l
"http://ftp.funet.fi/pub/mirrors/centos.org/6.4/os/x86_64"
> >>>   
> >>>       
> >> Does it work if you specify the driver name in the diskopts?  E.g.
> >>
> >>   --disk
/var/lib/libvirt/images/blktaptest01.img,size=8,driver_name=tap2
> >>
> >>     
> >
> > Yep, that works.
> >
> > I was mostly wondering how to specify/change the *default*,
> > so that both virt-install and virt-manager work without specifying
driver_name=tap2 ..
> >   
> 
> Ahh.
> 
> > Any ideas about that?
> >   
> 
> No, but I''m not that familiar with virt-{install,manager} code. 
Seems
> like a good question for virt-tools-list@redhat.com.
>
Ok, I''ll post there.

Thanks!

-- Pasi
 
> Regards,
> Jim
>