CentOS virt - Jan 2015 - CentOS 6 Xen 4.4.1 packages available on virt6-testing / libvirt blktap2 problems

On Tue, Dec 16, 2014 at 10:29:53PM +0200, Pasi K?rkk?inen
wrote:
> > 
> > * xend is now disabled by default.  You can enable it by running
> > chkconfig.  xend has been removed from the tree entirely in Xen 4.5,
> > so this should (hopefully) serve as a "wake-up-call" for
people to
> > begin the transition over to xend.
> > 
> > * A lot have things have changed -- please to test this so we can get
> > a good idea what may have broken.
> >
> 
> I'll test soon. Thanks a lot!
> 

Ok I just used a couple of hours testing Xen 4.4.1 rpms on CentOS 6.6 with Linux
3.10 dom0 kernel.
This session was all about xm/xend testing. I manually enabled xend first. 


What Works OK:
	- Manually creating/managing guests with xm and domU cfgfiles in /etc/xen and
LVM volumes as storage (phy backend).
	- Manually creating/managing guests with xm and domU cfgfiles in /etc/xen and
file images as storage (tap2:aio backend).
	- Using virt-install to install PV domUs using LVM volumes as storage (phy
backend).
	- Using virt-manager to install PV domUs using LVM volumes as storage (phy
backend).

What doesn't work:
	- Using virt-manager to install PV domUs using file images as storage (tap:aio
backend).


This libvirt/blktap2 file images failure with Xen 4.4 rpms is a regression from
Xen 4.2 rpms, where blktap2 works OK with libvirt/virt-install/virt-manager.

The problem is most probably the fact that we had custom patches included in the
xen4c6 libvirt rpms that we shipped with the Xen 4.2 rpms.
We had to add two patches, one patch to fix the blktap2 backend type in libvirt,
and one patch to fix the blktap2 backend type in virt-install or virt-manager,
i'm not totally sure which one it was. Those patches should be included in
the earlier libvirt source rpms, so we can check there. Or I can search thru my
emails, because I hunted that down earlier aswell.

It seems we still need those patches with the latest libvirt rpms too.

The actual problem is libvirt/virt-manager tries to configure tap:aio: backend,
which won't work.
It needs to be tap2:aio.

I get the exactly same behaviour with xm/xend. "tap:aio" stalls and
fails. "tap2:aio" works OK.


-- Pasi

On Tue, Jan 06, 2015 at 12:15:25AM +0200, Pasi K?rkk?inen
wrote:
> On Tue, Dec 16, 2014 at 10:29:53PM +0200, Pasi K?rkk?inen wrote:
> > > 
> > > * xend is now disabled by default.  You can enable it by running
> > > chkconfig.  xend has been removed from the tree entirely in Xen
4.5,
> > > so this should (hopefully) serve as a "wake-up-call"
for people to
> > > begin the transition over to xend.
> > > 
> > > * A lot have things have changed -- please to test this so we can
get
> > > a good idea what may have broken.
> > >
> > 
> > I'll test soon. Thanks a lot!
> > 
> 
> 
> Ok I just used a couple of hours testing Xen 4.4.1 rpms on CentOS 6.6 with
Linux 3.10 dom0 kernel.
> This session was all about xm/xend testing. I manually enabled xend first. 
> 
> 
> What Works OK:
> 	- Manually creating/managing guests with xm and domU cfgfiles in /etc/xen
and LVM volumes as storage (phy backend).
> 	- Manually creating/managing guests with xm and domU cfgfiles in /etc/xen
and file images as storage (tap2:aio backend).
> 	- Using virt-install to install PV domUs using LVM volumes as storage (phy
backend).
> 	- Using virt-manager to install PV domUs using LVM volumes as storage (phy
backend).
> 
> What doesn't work:
> 	- Using virt-manager to install PV domUs using file images as storage
(tap:aio backend).
>
Oh, and obviously "virt-install" fails aswell when trying to use file
images, same problem as with virt-manager.

Here's the virt-install commandline example you can use for testing:

virt-install -d -n blktaptest01 -r 2048 --vcpus=2 --disk
/var/lib/libvirt/images/blktaptest01.img,size=8 --vnc -p -b virbr0 -l
"http://ftp.funet.fi/pub/mirrors/centos.org/6.6/os/x86_64"


obviously you need to have a working libvirt-setup before running that command,
and the libvirt/dnsmasq virbr0 bridge as created by libvirtd:

- yum install libvirt libvirt-daemon libvirt-daemon-network
libvirt-driver-network libvirt-driver-xen virt-install virt-viewer virt-manager
python-virtinst xorg-x11-xauth
- service xend restart
- service libvirtd restart

> 
> This libvirt/blktap2 file images failure with Xen 4.4 rpms is a regression
from Xen 4.2 rpms, where blktap2 works OK with
libvirt/virt-install/virt-manager.
> 
> The problem is most probably the fact that we had custom patches included
in the xen4c6 libvirt rpms that we shipped with the Xen 4.2 rpms.
> We had to add two patches, one patch to fix the blktap2 backend type in
libvirt, and one patch to fix the blktap2 backend type in virt-install or
virt-manager, i'm not totally sure which one it was. Those patches should be
included in the earlier libvirt source rpms, so we can check there. Or I can
search thru my emails, because I hunted that down earlier aswell.
> 
> It seems we still need those patches with the latest libvirt rpms too.
> 
> The actual problem is libvirt/virt-manager tries to configure tap:aio:
backend, which won't work.
> It needs to be tap2:aio.
> 
> I get the exactly same behaviour with xm/xend. "tap:aio" stalls
and fails. "tap2:aio" works OK.
> 
Ok so digging into the email archives it seems earlier we patched
python-virtinst src.rpm,
which seems to be the component used by both virt-install and virt-manager for
new domain installations.

So we need to modify the virtinst/VirtualDisk.py file and change the:

DRIVER_TAP = "tap"

to

DRIVER_TAP = "tap2"

To change the default. 

After that change the libvirt generated domain xml looks like this, from both
virt-install and virt-manager and works OK:

   <disk type='file' device='disk'>
      <driver name='tap2' type='aio'/>
      <source file='/var/lib/libvirt/images/blktaptest01.img'/>
      <target dev='xvda' bus='xen'/>
    </disk>


(virsh dumpxml <domain>)


-- Pasi

On 01/05/2015 04:15 PM, Pasi K?rkk?inen wrote:
> On Tue, Dec 16, 2014 at 10:29:53PM +0200, Pasi K?rkk?inen wrote:
>>>
>>> * xend is now disabled by default.  You can enable it by running
>>> chkconfig.  xend has been removed from the tree entirely in Xen
4.5,
>>> so this should (hopefully) serve as a "wake-up-call" for
people to
>>> begin the transition over to xend.
>>>
>>> * A lot have things have changed -- please to test this so we can
get
>>> a good idea what may have broken.
>>>
>>
>> I'll test soon. Thanks a lot!
>>
> 
> 
> Ok I just used a couple of hours testing Xen 4.4.1 rpms on CentOS 6.6 with
Linux 3.10 dom0 kernel.
> This session was all about xm/xend testing. I manually enabled xend first. 
> 
> 
> What Works OK:
> 	- Manually creating/managing guests with xm and domU cfgfiles in /etc/xen
and LVM volumes as storage (phy backend).
> 	- Manually creating/managing guests with xm and domU cfgfiles in /etc/xen
and file images as storage (tap2:aio backend).
> 	- Using virt-install to install PV domUs using LVM volumes as storage (phy
backend).
> 	- Using virt-manager to install PV domUs using LVM volumes as storage (phy
backend).
> 
> What doesn't work:
> 	- Using virt-manager to install PV domUs using file images as storage
(tap:aio backend).
> 
> 
> This libvirt/blktap2 file images failure with Xen 4.4 rpms is a regression
from Xen 4.2 rpms, where blktap2 works OK with
libvirt/virt-install/virt-manager.
> 
> The problem is most probably the fact that we had custom patches included
in the xen4c6 libvirt rpms that we shipped with the Xen 4.2 rpms.
> We had to add two patches, one patch to fix the blktap2 backend type in
libvirt, and one patch to fix the blktap2 backend type in virt-install or
virt-manager, i'm not totally sure which one it was. Those patches should be
included in the earlier libvirt source rpms, so we can check there. Or I can
search thru my emails, because I hunted that down earlier aswell.
> 
> It seems we still need those patches with the latest libvirt rpms too.
> 
> The actual problem is libvirt/virt-manager tries to configure tap:aio:
backend, which won't work.
> It needs to be tap2:aio.
> 
> I get the exactly same behaviour with xm/xend. "tap:aio" stalls
and fails. "tap2:aio" works OK.
> 
Now with the new python-virtinst and then new kernel from here:


http://people.centos.org/hughesjr/xen4-test/

But with the new libvirt-1.2 and xen 4.4 from this repo, everything
seems to work with xend enabled.

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On Tue, Jan 06, 2015 at 01:55:57PM -0600, Johnny Hughes
wrote:
> > 
> > Ok I just used a couple of hours testing Xen 4.4.1 rpms on CentOS 6.6
with Linux 3.10 dom0 kernel.
> > This session was all about xm/xend testing. I manually enabled xend
first.
> > 
> > 
> > What Works OK:
> > 	- Manually creating/managing guests with xm and domU cfgfiles in
/etc/xen and LVM volumes as storage (phy backend).
> > 	- Manually creating/managing guests with xm and domU cfgfiles in
/etc/xen and file images as storage (tap2:aio backend).
> > 	- Using virt-install to install PV domUs using LVM volumes as storage
(phy backend).
> > 	- Using virt-manager to install PV domUs using LVM volumes as storage
(phy backend).
> > 
> > What doesn't work:
> > 	- Using virt-manager to install PV domUs using file images as storage
(tap:aio backend).
> > 
> > 
> > This libvirt/blktap2 file images failure with Xen 4.4 rpms is a
regression from Xen 4.2 rpms, where blktap2 works OK with
libvirt/virt-install/virt-manager.
> > 
> > The problem is most probably the fact that we had custom patches
included in the xen4c6 libvirt rpms that we shipped with the Xen 4.2 rpms.
> > We had to add two patches, one patch to fix the blktap2 backend type
in libvirt, and one patch to fix the blktap2 backend type in virt-install or
virt-manager, i'm not totally sure which one it was. Those patches should be
included in the earlier libvirt source rpms, so we can check there. Or I can
search thru my emails, because I hunted that down earlier aswell.
> > 
> > It seems we still need those patches with the latest libvirt rpms too.
> > 
> > The actual problem is libvirt/virt-manager tries to configure tap:aio:
backend, which won't work.
> > It needs to be tap2:aio.
> > 
> > I get the exactly same behaviour with xm/xend. "tap:aio"
stalls and fails. "tap2:aio" works OK.
> > 
> 
> Now with the new python-virtinst and then new kernel from here:
> 
> 
> http://people.centos.org/hughesjr/xen4-test/
> 
> But with the new libvirt-1.2 and xen 4.4 from this repo, everything
> seems to work with xend enabled.
> 
Yep, with the updated python-virtinst all works now, also with the Xen 4.4 rpms.

Thanks a lot!

-- Pasi