[Pkg-libvirt-maintainers] Bug#797513: Regression in support for custom CPU configuration

[Ben Hutchings]

Source: libvirt
Version: 1.2.18-2
Severity: important

Since the upgrade to 1.2.18-2, most of my VMs fail to start:

virsh # start sid
error: Failed to start domain sid
error: unsupported configuration: guest and host CPU are not compatible: host CPU vendor does not match required CPU vendor Intel

This is the CPU I have:

processor	: 0
vendor_id	: GenuineIntel
cpu family	: 6
model		: 42
model name	: Intel(R) Core(TM) i5-2540M CPU @ 2.60GHz
stepping	: 7
microcode	: 0x29
cpu MHz		: 825.703
cache size	: 3072 KB
physical id	: 0
siblings	: 4
core id		: 0
cpu cores	: 2
apicid		: 0
initial apicid	: 0
fpu		: yes
fpu_exception	: yes
cpuid level	: 13
wp		: yes
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 nopl xtopology nonstop_tsc aperfmperf eagerfpu pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm pcid sse4_1 sse4_2 x2apic popcnt tsc_deadline_timer aes xsave avx lahf_lm ida arat epb pln pts dtherm tpr_shadow vnmi flexpriority ept vpid xsaveopt
bugs		:
bogomips	: 5183.58
clflush size	: 64
cache_alignment	: 64
address sizes	: 36 bits physical, 48 bits virtual
power management:

[other 3 threads omitted]

and here's the CPU configuration for one of those domains:

  <cpu mode='custom' match='exact'>
    <model fallback='allow'>SandyBridge</model>
    <vendor>Intel</vendor>
    <feature policy='require' name='avx'/>
    <feature policy='require' name='tsc-deadline'/>
    <feature policy='require' name='dtes64'/>
    <feature policy='require' name='xsave'/>
    <feature policy='require' name='tm2'/>
    <feature policy='require' name='vmx'/>
    <feature policy='require' name='xtpr'/>
    <feature policy='require' name='pbe'/>
    <feature policy='require' name='est'/>
    <feature policy='require' name='smx'/>
    <feature policy='require' name='lm'/>
    <feature policy='require' name='tm'/>
    <feature policy='require' name='sse4.1'/>
    <feature policy='require' name='sse4.2'/>
    <feature policy='require' name='pclmuldq'/>
    <feature policy='require' name='acpi'/>
    <feature policy='require' name='osxsave'/>
    <feature policy='require' name='aes'/>
    <feature policy='require' name='ht'/>
    <feature policy='require' name='lahf_lm'/>
    <feature policy='require' name='pdcm'/>
    <feature policy='require' name='ds'/>
    <feature policy='require' name='invtsc'/>
    <feature policy='require' name='rdtscp'/>
    <feature policy='require' name='ss'/>
    <feature policy='require' name='pcid'/>
    <feature policy='require' name='cx16'/>
    <feature policy='require' name='pse36'/>
    <feature policy='require' name='ds_cpl'/>
    <feature policy='require' name='popcnt'/>
    <feature policy='require' name='x2apic'/>
    <feature policy='disable' name='syscall'/>
  </cpu>

(Why a custom CPU configuration?  Because 'copy host configuration'
does something crazy.  The VM gets an 'Atom N270' (a 32-bit processor
in reality) with a random assortment of CPU flags, including 'lm' but
not 'syscall'.  llvmpipe also seems to be unhappy with this, resulting
in a sadface when gdm3 starts.)

If I delete the <cpu> element entirely from the XML file, the VM works
again.

Ben.

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

Kernel: Linux 4.1.0-2-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_GB.utf8, LC_CTYPE=en_GB.utf8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)