Re: [libvirt] [frankschreuder@outlook.com: Fwd: Reproducible live disk detach bug]

Hi Laine, I'm sorry for starting 3 threads with the same topic, seems like my mail was heavily delayed yesterday. [ removing personal mail ] Op 8/7/2015 om 12:24 AM schreef Laine Stump: >>>Subject: Reproducible live disk detach bug >>> >>>Hey guys, >>> >>>I am currently running into a reproducible libvirt bug when I detach a >>>disk from a running VM using libvirt 1.2.18 and qemu 2.3.0. >>> >>>I can attach a disk to a running VM without any problems. >>>During the attach operation I don't create a disk alias name, which >>>results in libvirt generating an unique alias. >>>Using virsh dumpxml I get the following output(snippet): >>> >>><disk type='file' device='disk'> >>> <driver name='qemu' type='raw' cache='none'/> >>> <source file='/var/local/mnt/test-storage/test-storage.raw'/> >>> <backingStore/> >>> <target dev='vde' bus='virtio'/> >>> <iotune> >>> <read_bytes_sec>94371840</read_bytes_sec> >>> <write_bytes_sec>31457280</write_bytes_sec> >>> <read_iops_sec>1000</read_iops_sec> >>> <write_iops_sec>200</write_iops_sec> >>> </iotune> >>> <alias name='virtio-disk4'/> >>> <address type='pci' domain='0x0000' bus='0x00' slot='0x09' function='0x0'/> >>></disk> >>> >>>As you can see, libvirt generates 'virtio-disk4' as an alias. But as >>>soon as I try to detach the disk from the running VM, I will receive the >>>following two errors in my libvirt log: >>> >>>2015-08-06 10:48:59.943+0000: 11657: warning : >>>qemuMonitorJSONHandleDeviceDeleted:939 : missing device in device >>>deleted event >>>2015-08-06 10:48:59.945+0000: 11662: error : >>>qemuMonitorTextDriveDel:2594 : operation failed: deleting >>>drive-virtio-disk4 drive failed: 2015-08-06T10:48:59.945058Z Device >>>'drive-virtio-disk4' not found >>> >>>Apparently libvirt tries to detach the disk with a drive- prefix, which >>>doesn't exist? >I can't tell you right off why the failure message is there, but the >alias with the added "drive-" is easily explained. > >Each <disk> element in the libvirt config corresponds to two entities in >the qemu virtual machine - a "device" component (what is seen by the >guest) and a "drive" component (what resources are used on the host to >back up that device). Each of these corresponds to a separate qemu >commandline argument (named "-device" and "-drive"), and each of those >must have a different, unique "id" option. For example, this is what is >added to my qemu commandline when I add a virtio disk named >"rawhide.qcow2" to my virtual machine: > >-drive >file=/var/lib/libvirt/images/rawhide.qcow2,if=none,id=drive-virtio-disk0,format=qcow2 >-device >virtio-blk-pci,scsi=off,bus=pci.2,addr=0x5,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=1 > > >If you look at the status XML of the domain while it is running, you'll >see that the <alias> for the disk element is "virtio-disk0", and that's >what is given to the -device half of the disk as its qemu id. The -drive >half uses "drive-$alias" as its qemu id though (you'll notice that the >-device half references that id with its "drive" option - that's how the >two halves are tied together by qemu). > >So, there is nothing unusual about qemu wanting to delete something >called drive-virtio-disk4 when you have a <disk> with >alias='virtio-disk4'. It obviously isn't right that an error message is >being logged. Something sounds familiar about the "missing device in >device deleted event" message, but I can't recall details. Does anyone >else have a better memory? Frank - would it be possible for you to try >this same sequence of events with the same libvirt and an older qemu >(and/or vice-versa)? > I have some more interesting debug information. I'm -not- able to reproduce it on libvirt 1.2.11 - qemu 2.3.0 and libvirt 1.2.11 - qemu 1.7.1 using a FreeBSD VM. I'm able to reproduce the errors with libvirt 1.2.11 - qemu 2.3.0 and libvirt 1.2.18 - qemu 2.3.0 using a Debian VM. Seems like the error triggers depending on the guest OS? During hot-unplugging of network interfaces libvirt also triggers the same error on a Debian VM: 2015-08-06 10:48:59.945+0000: 11662: error : qemuMonitorJSONHandleDeviceDeleted:939 : missing device in device deleted event I gathered some logging information with info level logging enabled while detaching a disk: http://pastebin.com/raw.php?i=vVLuavG2