On 08/06/2015 05:00 PM, Richard W.M. Jones wrote: > Forwarding from Frank Schreuder who was having some issues > sending this to the mailing list. > > ----- Begin forwarded message ----- > >> 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)? -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list