Bug#844446: Still an issue

[Marcel Meckel <debian@thermoman.de>]

This is still an issue with latest kernel in stretch.

KVM/QEMU Guest VM running Debian stretch on top of Host
running Debian jessie with libvirt guest settings:

---snip---
  <vcpu>4</vcpu>
  <cpu mode='host-passthrough'>
    <topology sockets='1' cores='4' threads='1'/>
  </cpu>
---snip---

Processor on Host is:

processor       : 0
vendor_id       : GenuineIntel
cpu family      : 6
model           : 94
model name      : Intel(R) Core(TM) i7-6700 CPU @ 3.40GHz
stepping        : 3
microcode       : 0x55
cpu MHz         : 800.000
cache size      : 8192 KB
physical id     : 0
siblings        : 8
core id         : 0
cpu cores       : 4
apicid          : 0
initial apicid  : 0
fpu             : yes
fpu_exception   : yes
cpuid level     : 22
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 pdpe1gb rdtscp lm constant_tsc arch_perfmon p
ebs bts rep_good nopl xtopology nonstop_tsc aperfmperf eagerfpu pni 
pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 fma cx16 xtpr pdcm 
pcid sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_t
imer aes xsave avx f16c rdrand lahf_lm abm 3dnowprefetch ida arat epb 
xsaveopt pln pts dtherm tpr_shadow vnmi flexpriority ept vpid fsgsbase 
tsc_adjust bmi1 hle avx2 smep bmi2 erms invpcid rtm m
px rdseed adx smap clflushopt
bogomips        : 6816.04
clflush size    : 64
cache_alignment : 64
address sizes   : 39 bits physical, 48 bits virtual
power management:


Guest VM running

ii  linux-base                 4.5
ii  linux-image-4.7.0-1-amd64  4.7.8-1    <-- works fine
ii  linux-image-4.8.0-2-amd64  4.8.15-2   <-- kernel panic
ii  linux-image-amd64          4.8+77

Workaround

Removing libvirt block

---snip---
  <cpu mode='host-passthrough'>
    <topology sockets='1' cores='4' threads='1'/>
  </cpu>
---snip---

fixes the problem, guest VM kernel boots without problems.