[Bug 685991] [NEW] cannot kill kvm process that uses 'tap'

[Jamie Strandboge]

Public bug reported:

Binary package hint: qemu-kvm

On up to date Natty and kernel 2.6.37-7.19-generic I cannot kill kvm processes when they are started with 'tap', even with 'kill -9'. This has been true for at least the last several Natty kernels. If I reboot into a maverick kernel, all is well. I first noticed this when I tried to stop a VM in libvirt. The qemu-kvm command line:
/usr/bin/kvm -S -M pc-0.12 -enable-kvm -m 384 -smp 1,sockets=1,cores=1,threads=1 -name sec-dapper-amd64 -uuid 29810304-fac2-d840-ab12-21a001a66e54 -nodefconfig -nodefaults -chardev socket,id=monitor,path=/var/lib/libvirt/qemu/sec-dapper-amd64.monitor,server,nowait -mon chardev=monitor,mode=readline -rtc base=utc -boot c -drive file=/home/jamie/vms/kvm/sec-dapper-amd64/disk0.qcow2,if=none,id=drive-ide0-0-0,format=qcow2,cache=writeback -device ide-drive,bus=ide.0,unit=0,drive=drive-ide0-0-0,id=ide0-0-0 -netdev tap,fd=40,id=hostnet0 -device e1000,netdev=hostnet0,id=net0,mac=52:54:00:9e:ae:5d,bus=pci.0,addr=0x3 -usb -vnc 127.0.0.1:0 -vga cirrus -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x4

Trying to shutdown the VM results in the following in dmesg:
[39656.368496] unregister_netdevice: waiting for vnet0 to become free. Usage count = 1

Trying to find a reduced test case, I tried:
$ /usr/bin/kvm -M pc -m 256 -no-acpi -drive file=./disk0.qcow2 -net nic,vlan=0 -net tap,vlan=0,ifname=tap0

This resulted in a VM that would not start (it uses /etc/qemu-ifup since
I did not specify a 'script=' parameter). This kvm process is unkillable
with kill -9, but nothing in dmesg.

Then I tried the following:
/usr/bin/kvm -M pc -m 256 -no-acpi -drive file=./disk0.qcow2 -net nic,vlan=0 -net tap,vlan=0,ifname=tap0,script=

This resulted in a VM that would start, but the kvm process is
unkillable with kill -9, but nothing in dmesg.

ProblemType: Bug
DistroRelease: Ubuntu 11.04
Package: qemu-kvm 0.13.0+noroms-0ubuntu9
ProcVersionSignature: Ubuntu 2.6.37-7.19-generic 2.6.37-rc3
Uname: Linux 2.6.37-7-generic x86_64
Architecture: amd64
Date: Mon Dec  6 08:30:39 2010
EcryptfsInUse: Yes
InstallationMedia: Ubuntu 10.04 LTS "Lucid Lynx" - Release amd64 (20100427.1)
KvmCmdLine:
 UID        PID  PPID  C    SZ   RSS PSR STIME TTY          TIME CMD
 root      4536     1  0 29363  3340   2 08:18 ?        00:00:00 /usr/bin/kvm -M pc -m 256 -no-acpi -drive file=./disk0.qcow2 -net nic,vlan=0 -net tap,vlan=0,ifname=tap0
 root      4633     1  7 108952 253696 1 08:19 ?        00:00:51 /usr/bin/kvm -M pc -m 256 -no-acpi -drive file=./disk0.qcow2 -net nic,vlan=0 -net tap,vlan=0,ifname=tap0,script=
MachineType: LENOVO 5129CTO
ProcEnviron:
 PATH=(custom, user)
 LANG=en_US.utf8
 SHELL=/bin/bash
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-2.6.37-7-generic root=UUID=82571cfb-fdda-4d2f-b708-f8924aa0fe21 ro quiet splash
SourcePackage: qemu-kvm
dmi.bios.date: 04/20/2010
dmi.bios.vendor: LENOVO
dmi.bios.version: 6QET44WW (1.14 )
dmi.board.name: 5129CTO
dmi.board.vendor: LENOVO
dmi.board.version: Not Available
dmi.chassis.asset.tag: No Asset Information
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: Not Available
dmi.modalias: dmi:bvnLENOVO:bvr6QET44WW(1.14):bd04/20/2010:svnLENOVO:pn5129CTO:pvrThinkPadX201s:rvnLENOVO:rn5129CTO:rvrNotAvailable:cvnLENOVO:ct10:cvrNotAvailable:
dmi.product.name: 5129CTO
dmi.product.version: ThinkPad X201s
dmi.sys.vendor: LENOVO

** Affects: linux (Ubuntu)
     Importance: Undecided
         Status: New

** Affects: qemu-kvm (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: amd64 apport-bug natty

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https://bugs.launchpad.net/bugs/685991

Title:
  cannot kill kvm process that uses 'tap'