[libvirt] libvirt-libxl driver defaulting to tap disk and not working (ubuntu 12.10 + xen 4.5 + libvirt 1.2.3 + openstack)

[Jim Fehlig]

Tian, Shuangtai wrote:
> Hi, Jim
> The blktap seems not a module in xen 4.5, when I tried the load it , can not find the module, is there something wrong I did?
>   

It would be provided by your dom0 kernel, not Xen.  The Ubuntu Xen
kernel doesn't provide a blktap module?

Regards,
Jim

> BTW ,I compiled the xen4.5 by myself.
> Thanks ! 
>
> -----Original Message-----
> From: Jim Fehlig [mailto:jfehlig at suse.com] 
> Sent: Friday, April 18, 2014 11:52 PM
> To: Tian, Shuangtai
> Cc: libvir-list at redhat.com
> Subject: Re: [libvirt] libvirt-libxl driver defaulting to tap disk and not working (ubuntu 12.10 + xen 4.5 + libvirt 1.2.3 + openstack)
>
> Tian, Shuangtai wrote:
>   
>> HI
>>
>> I am an openstacker, when I used the latest libvirt and xen code to 
>> run the openstack. Can not create the vm.
>>
>> there is an error in libxl log, you can see the log:
>>
>> Os : Ubuntu 12.10
>>
>>  
>>
>> Compiled against library: libvirt 1.2.3
>>
>> Using library: libvirt 1.2.3
>>
>> Using API: Xen 1.2.3
>>
>> Running hypervisor: Xen 4.5.0
>>
>>  
>>
>> libxl: debug: libxl_create.c:1356:do_domain_create: ao 0x7f7894002810:
>> create: how=(nil) callback=(nil) poller=0x7f7894001bb0
>>
>> libxl: debug: libxl_device.c:251:libxl__device_disk_set_backend: Disk 
>> vdev=xvda spec.backend=tap
>>
>> libxl: debug: libxl_device.c:210:disk_try_backend: Disk vdev=xvda, 
>> backend tap unsuitable because blktap not available
>>
>>     
>
> In addition to John's suggestions, try loading a blktap module in dom0. 
> It should work if a blktap driver is available.
>
> Regards,
> Jim
>
>   
>> libxl: error: libxl_device.c:289:libxl__device_disk_set_backend: no 
>> suitable backend for disk xvda
>>
>> libxl: debug: libxl_event.c:1739:libxl__ao_complete: ao
>> 0x7f7894002810: complete, rc=-3
>>
>> libxl: debug: libxl_create.c:1370:do_domain_create: ao 0x7f7894002810:
>> inprogress: poller=0x7f7894001bb0, flags=ic
>>
>> libxl: debug: libxl_event.c:1711:libxl__ao__destroy: ao
>> 0x7f7894002810: destroy
>>
>>  
>>
>> The blktap does work, and I also find the same error someone has 
>> posted,
>> (http://www.redhat.com/archives/libvir-list/2013-February/msg01124.htm
>> l)
>>
>> When I change the type to “phy”, it also doesnot work. And try to 
>> change the type to other options, also does not work.
>>
>> Can someone give me some suggestions?
>>
>> Thanks !
>>
>>  
>>
>> The XML from the openstack is :
>>
>> <domain type="xen">
>>
>>   <uuid>9e9ed86c-8892-40da-acd1-31ec6303abfe</uuid>
>>
>>   <name>instance-00000001</name>
>>
>>   <memory>524288</memory>
>>
>>   <vcpu>1</vcpu>
>>
>>   <os>
>>
>>     <type>xen</type>
>>
>>    
>> <kernel>/opt/stack/data/nova/instances/9e9ed86c-8892-40da-acd1-31ec630
>> 3abfe/kernel</kernel>
>>
>>    
>> <initrd>/opt/stack/data/nova/instances/9e9ed86c-8892-40da-acd1-31ec630
>> 3abfe/ramdisk</initrd>
>>
>>     <cmdline>ro root=/dev/xvda</cmdline>
>>
>>   </os>
>>
>>   <features>
>>
>>    <acpi/>
>>
>>     <apic/>
>>
>>   </features>
>>
>>   <clock offset="utc"/>
>>
>>   <devices>
>>
>>     <disk type="file" device="disk">
>>
>>       <driver name="tap2" type="raw" cache="none"/>
>>
>>       <source
>> file="/opt/stack/data/nova/instances/9e9ed86c-8892-40da-acd1-31ec6303a
>> bfe/disk"/>
>>
>>       <target bus="xen" dev="xvda"/>
>>
>>     </disk>
>>
>>     <disk type="file" device="cdrom">
>>
>>       <driver name="tap2" type="raw" cache="none"/>
>>
>>       <source
>> file="/opt/stack/data/nova/instances/9e9ed86c-8892-40da-acd1-31ec6303a
>> bfe/disk.config"/>
>>
>>       <target bus="ide" dev="xvdd"/>
>>
>>     </disk>
>>
>>     <interface type="bridge">
>>
>>       <mac address="fa:16:3e:d8:c3:c0"/>
>>
>>       <source bridge="br100"/>
>>
>>       <filterref 
>> filter="nova-instance-instance-00000001-fa163ed8c3c0"/>
>>
>>     </interface>
>>
>>     <console type="pty"/>
>>
>>     <graphics type="vnc" autoport="yes" keymap="en-us"
>> listen="127.0.0.1"/>
>>
>>     <video>
>>
>>       <model type="xen"/>
>>
>>     </video>
>>
>>   </devices>
>>
>> </domain>
>>
>>  
>>
>>  
>>
>>  
>>
>> Best regards,
>>
>> Tian, Shuangtai
>>
>>  
>>
>> ----------------------------------------------------------------------
>> --
>>
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>>