[ovirt-users] qemu cgroup_controllers

Martin Polednik mpolednik at redhat.com
Mon Jun 6 09:39:59 EDT 2016 

On 06/06/16 16:15 +0300, Дмитрий Глушенок wrote:
>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.

It should be 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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