[ovirt-users] qemu cgroup_controllers

Дмитрий Глушенок glush at jet.msk.su
Mon Jun 6 13:15:31 UTC 2016 

So, libvirt behaves differently with custom partition? My assumption was that it will perform the same changes. I will have in mind in case oVirt 4 will be released too late.
May be I wrote incorrectly - in oVirt 4.0 RC1 scsi pass-through already working.

--
Dmitry Glushenok
Jet Infosystems
http://www.jet.msk.su <http://www.jet.msk.su/>+7-495-411-7601 (ext. 1237)

> 6 июня 2016 г., в 13:35, Martin Polednik <mpolednik at redhat.com> написал(а):
> 
> On 06/06/16 13:26 +0300, Дмитрий Глушенок wrote:
>> Hello Martin,
>> 
>> Thank you for your time. It is clear how to create partition and assign it to a VM. But libvirt manipulates with contents of devices.list and I didn't find a way to put my devices into devices.list and stop libvirt from removing them.
> 
> That is, by the way, pretty interesting. I have tried it right now and
> when using custom partition, libvirt doesn't touch my devices.list.
> 
> It might make sense to file a libvirt bug.
> 
>> Anyway, it looks like that the best solution will be using oVirt 4.0 where scsi pass-through have been fixed.
> 
> Hoping so!
> 
>> --
>> Dmitry Glushenok
>> Jet Infosystems
>> http://www.jet.msk.su <http://www.jet.msk.su/>+7-495-411-7601 (ext. 1237)
>> 
>>> 6 июня 2016 г., в 12:33, Martin Polednik <mpolednik at redhat.com> написал(а):
>>> 
>>> On 03/06/16 14:05 +0300, Дмитрий Глушенок wrote:
>>>> Thank you Martin!
>>>> 
>>>> Actually I tried the workaround hook, provided in [2], but then VDSM (oVirt 3.6.6) tries to interpret hostdev in XML as PCI device, which leads to:
>>>> 
>>>> ::The vm start process failed
>>>> Traceback (most recent call last):
>>>> File "/usr/share/vdsm/virt/vm.py", line 703, in _startUnderlyingVm
>>>>  self._run()
>>>> File "/usr/share/vdsm/virt/vm.py", line 1949, in _run
>>>>  self._domDependentInit()
>>>> File "/usr/share/vdsm/virt/vm.py", line 1797, in _domDependentInit
>>>>  self._getUnderlyingVmDevicesInfo()
>>>> File "/usr/share/vdsm/virt/vm.py", line 1738, in _getUnderlyingVmDevicesInfo
>>>>  self._getUnderlyingHostDeviceInfo()
>>>> File "/usr/share/vdsm/virt/vm.py", line 4277, in _getUnderlyingHostDeviceInfo
>>>>  **self._getUnderlyingDeviceAddress(source))
>>>> TypeError: pci_address_to_name() got an unexpected keyword argument 'target'
>>>> 
>>>> XML part was:
>>>> <hostdev managed="no" mode="subsystem" rawio="yes" type="scsi">
>>>> 	<source>
>>>> 		<adapter name="scsi_host2"/>
>>>> 		<address bus="0" target="1" unit="0"/>
>>>> 	</source>
>>>> </hostdev>
>>>> <hostdev managed="no" mode="subsystem" rawio="yes" type="scsi">
>>>> 	<source>
>>>> 		<adapter name="scsi_host2"/>
>>>> 		<address bus="0" target="2" unit="0"/>
>>>> 	</source>
>>>> </hostdev>
>>>> 
>>>> 
>>>> As of creating custom partition - by default machine.slice has "a *:* rwm" in devices.list. But for every new VM libvirt removes *:* mask and fills the list with actually needed devices (as I understand the process). For example:
>>>> 
>>>> c 136:* rw
>>>> c 1:3 rw
>>>> c 1:7 rw
>>>> c 1:5 rw
>>>> c 1:8 rw
>>>> c 1:9 rw
>>>> c 5:2 rw
>>>> c 10:232 rw
>>>> c 253:0 rw
>>>> c 10:228 rw
>>>> c 10:196 rw
>>>> 
>>>> What I'm looking for is a way to tell libvirt about my additional devices without breaking oVirt.
>>> 
>>> The solution would be creating your own partition and somehow (e.g.
>>> VDSM hook) appending
>>> 
>>> <resource>
>>>  <partition>/machine/custom</partition>
>>> </resource>
>>> 
>>> to the libvirt's <domain> element. I'm not sure how feasible creating
>>> your own partition is though. I've tried the process as follows:
>>> 
>>> $ cat ~/create-partition.sh
>>> # sh ~/create-partition.sh
>>> for i in blkio cpu,cpuacct cpuset devices freezer memory net_cls perf_event
>>> do
>>>  mkdir /sys/fs/cgroup/$i/machine.slice/custom.partition
>>> done
>>> 
>>> for i in cpuset.cpus cpuset.mems
>>> do
>>>  cat /sys/fs/cgroup/cpuset/machine.slice/$i > /sys/fs/cgroup/cpuset/machine.slice/custom.partition/$i
>>> done
>>> 
>>> (creates /machine/custom partition).
>>> Now, we can create vdsm before_vm_start hook that will set given partition
>>> for the VM:
>>> 
>>> $ pwd /usr/libexec/vdsm/hooks/before_vm_start
>>> $ cat 10_cgroups
>>> 
>>> #!/usr/bin/python
>>> 
>>> import hooking
>>> 
>>> 
>>> def custom_partition(domxml):
>>>  resource = domxml.createElement('resource')
>>>  partition = domxml.createElement('partition')
>>>  partition_text = domxml.createTextNode('/machine/custom')
>>>  partition.appendChild(partition_text)
>>>  resource.appendChild(partition)
>>> 
>>>  return resource
>>> 
>>> domxml = hooking.read_domxml()
>>> domain = domxml.getElementsByTagName('domain')[0]
>>> domain.appendChild(custom_partition(domxml))
>>> hooking.write_domxml(domxml)
>>> 
>>>> --
>>>> Dmitry Glushenok
>>>> Jet Infosystems
>>>> http://www.jet.msk.su
>>>> +7-495-411-7601 (ext. 1237)
>>>> 
>>>>> 3 июня 2016 г., в 12:24, Martin Polednik <mpolednik at redhat.com> написал(а):
>>>>> 
>>>>> On 03/06/16 11:48 +0300, Дмитрий Глушенок wrote:
>>>>>> Hello!
>>>>>> 
>>>>>> Is it possible to tell libvirt to add specific devices to qemu cgroup? By somehow enumerating the devices in XML using a hook for example.
>>>>>> I'm passing scsi-generic disks (/dev/sgX) to VM using qemucmdline hook and it doesn't work until I remove "devices" from cgroup_controllers in qemu.conf.
>>>>> 
>>>>> One way to achieve this is creating a hook to generate the scsi device
>>>>> XML instead of modifying qemu cmdline directly. Libvirt assumes
>>>>> ownership of all devices created in the XML and therefore adds them to
>>>>> the machine cgroup.
>>>>> 
>>>>> Example of the XML taken from [1]:
>>>>> <devices>
>>>>> <hostdev mode='subsystem' type='scsi' sgio='filtered' rawio='yes'>
>>>>>     <source>
>>>>>         <adapter name='scsi_host0'/>
>>>>>         <address bus='0' target='0' unit='0'/>
>>>>>     </source>
>>>>>     <readonly/>
>>>>>     <address type='drive' controller='0' bus='0' target='0' unit='0'/>
>>>>> </hostdev>
>>>>> </devices>
>>>>> 
>>>>> There is slight issue with this approach outlined in [2].
>>>>> 
>>>>> If you want to keep the qemu approach, I think creating a custom
>>>>> partition and moving devices there would be the cleanest approach. In
>>>>> this case, [3] could help but I'm not entirely sure if that would
>>>>> solve the issue.
>>>>> 
>>>>> [1] https://libvirt.org/formatdomain.html
>>>>> [2] https://bugzilla.redhat.com/show_bug.cgi?id=1325485
>>>>> [3] https://libvirt.org/cgroups.html
>>>>>> --
>>>>>> Dmitry Glushenok
>>>>>> Jet Infosystems
>>>>>> http://www.jet.msk.su
>>>>>> +7-495-411-7601 (ext. 1237)
>>>>>> 
>>>>>> _______________________________________________
>>>>>> Users mailing list
>>>>>> Users at ovirt.org
>>>>>> http://lists.ovirt.org/mailman/listinfo/users
>> 

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