[Pkg-libvirt-maintainers] Bug#742076: libvirt-bin: setvcpus command fails to shrink the numbers of vcpu

[Loïc REVEST]

Package: libvirt-bin
Version: 0.9.12.3-1
Severity: normal

Hi,

I faced an issue while attempting to decrease the number of vcpus one of my guest runs on, from 2 to only 1.

vcpu definition in my <domain> definition file: <vcpu placement='static'>2</vcpu>

Although the following command (in virsh environnment): 

"setvcpus <domain> 1"

issues the following output: 

"error: internal error got wrong number of vCPU pids from QEMU monitor. got 2, wanted 1"

libvirt seems to take that request into account :

virsh # vcpuinfo <domain>
VCPU:           0
CPU:            1
State:          running
CPU time:       178909,3s
CPU Affinity:   yyy

virsh # vcpucount <domain>
maximum      config         2
maximum      live           2
current      config         2
current      live           1

While on the guest side a cat /proc/cpuinfo still gives back two cpu available.

Unless I'm mistaken somewhere in my use of setvcpus, I think the previous command left my host/guest in an inconsistent state. The command setvcpus <domain> 2 runs flawlessy and gives me back a "consistent" output of vcpuinfo/vcpucount regarding the guest /proc/cpuinfo.

Regards and thanks in advance for any feedback/comment,

Loïc REVEST

-- System Information:
Debian Release: 7.4
  APT prefers stable-updates
  APT policy: (500, 'stable-updates'), (500, 'stable')
Architecture: amd64 (x86_64)

Kernel: Linux 3.2.0-4-amd64 (SMP w/3 CPU cores)
Locale: LANG=fr_FR.UTF-8, LC_CTYPE=fr_FR.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash

Versions of packages libvirt-bin depends on:
ii  adduser             3.113+nmu3
ii  gettext-base        0.18.1.1-9
ii  libblkid1           2.20.1-5.3
ii  libc6               2.13-38+deb7u1
ii  libcap-ng0          0.6.6-2
ii  libdbus-1-3         1.6.8-1+deb7u1
ii  libdevmapper1.02.1  2:1.02.74-8
ii  libgcrypt11         1.5.0-5+deb7u1
ii  libgnutls26         2.12.20-8+deb7u1
ii  libnetcf1           0.1.9-2
ii  libnl1              1.1-7
ii  libnuma1            2.0.8~rc4-1
ii  libparted0debian1   2.3-12
ii  libpcap0.8          1.3.0-1
ii  libpciaccess0       0.13.1-2
ii  libreadline6        6.2+dfsg-0.1
ii  libsasl2-2          2.1.25.dfsg1-6+deb7u1
ii  libudev0            175-7.2
ii  libvirt0            0.9.12.3-1
ii  libxml2             2.8.0+dfsg1-7+nmu2
ii  libyajl2            2.0.4-2
ii  logrotate           3.8.1-4

Versions of packages libvirt-bin recommends:
ii  bridge-utils    1.5-6
ii  dmidecode       2.11-9
ii  dnsmasq-base    2.62-3+deb7u1
ii  ebtables        2.0.10.4-1
ii  gawk            1:4.0.1+dfsg-2.1
ii  iproute         20120521-3+b3
ii  iptables        1.4.14-3.1
ii  libxml2-utils   2.8.0+dfsg1-7+nmu2
ii  netcat-openbsd  1.105-7
ii  parted          2.3-12
ii  qemu-kvm        1.1.2+dfsg-6

Versions of packages libvirt-bin suggests:
pn  policykit-1  <none>
pn  radvd        <none>

-- Configuration Files:
/etc/libvirt/qemu.conf changed [not included]

-- no debconf information