[Pkg-libvirt-maintainers] Bug#841778: fails to start qemu VMs when <model fallback='allow'>qemu64</model> is set

[Evgeni Golov]

Package: libvirt-daemon
Version: 2.3.0-3
Severity: important

Ohai,

since some time (probably since 2.3.0, but I didn't test exactly), VMs created by vagrant-libvirt fail to start on my laptop with the following error:
error: the CPU is incompatible with host CPU: Host CPU does not provide required features: svm

Technically, this is totally true, as I have an Intel CPU, and thus have "only" support for vmx, not svm.

The VM is defined with the following cpu config:
  <cpu mode='host-model'>
    <model fallback='allow'>qemu64</model>
  </cpu>

Changing this to
  <cpu mode='host-model'>
    <model fallback='allow'/>
  </cpu>
or
  <cpu mode='host-model'>
    <model fallback='allow'>pentium</model>
  </cpu>
makes the VM boot just fine. In both cases the CPU visible inside the VM is a Nehalem/Westmere, which matches the physical i7 in my laptop. But the machine has no vmx flag, as I did not enable nesting for kvm_intel.

Now the obvious questions are:
* why does setting fallback to qemu64 fail?
* why did it work before?
* is it actually a libvirt bug, or should vagrant-libvirt behave differently?

Greets
Evgeni

PS: My system is:
model name	: Intel(R) Core(TM) i7 CPU       L 620  @ 2.00GHz
flags		: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx rdtscp lm constant_tsc arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc aperfmperf eagerfpu pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm sse4_1 sse4_2 popcnt aes lahf_lm tpr_shadow vnmi flexpriority ept vpid dtherm ida arat


-- System Information:
Debian Release: stretch/sid
  APT prefers unstable
  APT policy: (500, 'unstable'), (500, 'testing'), (1, 'experimental')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.7.0-1-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages libvirt-daemon depends on:
ii  libapparmor1        2.10.95-5
ii  libaudit1           1:2.6.7-1
ii  libavahi-client3    0.6.32-1
ii  libavahi-common3    0.6.32-1
ii  libblkid1           2.28.2-1
ii  libc6               2.24-5
ii  libcap-ng0          0.7.7-3
ii  libdbus-1-3         1.10.12-1
ii  libdevmapper1.02.1  2:1.02.133-1
ii  libfuse2            2.9.7-1
ii  libgnutls30         3.5.5-2
ii  libnetcf1           1:0.2.8-1+b1
ii  libnl-3-200         3.2.27-1
ii  libnl-route-3-200   3.2.27-1
ii  libnuma1            2.0.11-1
ii  libparted2          3.2-16+b1
ii  libpcap0.8          1.7.4-3
ii  libpciaccess0       0.13.4-1
ii  librados2           0.80.11-1.1
ii  librbd1             0.80.11-1.1
ii  libsasl2-2          2.1.26.dfsg1-15
ii  libselinux1         2.5-3
ii  libssh2-1           1.7.0-1
ii  libudev1            231-9
ii  libvirt0            2.3.0-3
ii  libxen-4.6          4.6.0-1+nmu2
ii  libxenstore3.0      4.6.0-1+nmu2
ii  libxml2             2.9.4+dfsg1-2
ii  libyajl2            2.1.0-2

Versions of packages libvirt-daemon recommends:
ii  libxml2-utils   2.9.4+dfsg1-2
ii  netcat-openbsd  1.105-7
ii  qemu            1:2.7+dfsg-1
ii  qemu-kvm        1:2.7+dfsg-1

Versions of packages libvirt-daemon suggests:
ii  libvirt-daemon-system  2.3.0-3

-- no debconf information