[libvirt-users] LibVirt query CPU Model support and restore operation

[akhilesh rawat]

hello ,

thanks for comments .

I tried now with force options for CPU flag which were not supported . Now
the command with non fully supported CPU model gets executed ,  But i am
surprised to see that still Guest  cpu model is not changed and still same
as host cpu model(SAndy Bridge)

Why don't i see the model as HAswell now , could you please comment.

Command used :

virt-install --virt-type kvm --name controller-0  --cpu
Haswell-noTSX,+fma,+movbe,+fsgsbase,+bmi1,+avx2,+smep,+bmi2,+erms,+invpcid
--ram=8120 --vcpus=4,sockets=1

Linux process for KVM :

7479     1 37 10:13 ?        01:13:21 /usr/libexec/qemu-kvm -name
controller-0 -S -machine pc-i440fx-rhel7.0.0,accel=kvm,usb=off *-cpu
SandyBridge,*+fma,+pcid,+movbe,+fsgsbase,+bmi1,+avx2,+smep,+bmi2,+erms,+invpcid
-m 8120 -realtime mlock=off -smp 4,sockets=1,cores=4,threads=1



cpu guest :
processor    : 0
vendor_id    : GenuineIntel
cpu family    : 6
model        : 42
model name    : Intel Xeon E312xx (Sandy Bridge)
stepping    : 1
microcode    : 0x1
cpu MHz        : 1994.450
cache size    : 4096 KB
physical id    : 0
siblings    : 4
core id        : 0
cpu cores    : 4
apicid        : 0
initial apicid    : 0
fpu        : yes
fpu_exception    : yes
cpuid level    : 13
wp        : yes
flags        : fpu de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov
pat pse36 clflush mmx fxsr sse sse2 ht syscall nx rdtscp lm constant_tsc
rep_good nopl eagerfpu pni pclmulqdq ssse3 cx16 pcid sse4_1 sse4_2 x2apic
popcnt tsc_deadline_timer aes xsave avx hypervisor lahf_lm xsaveopt
bogomips    : 3988.90
clflush size    : 64
cache_alignment    : 64
address sizes    : 46 bits physical, 48 bits virtual
power management:


CPU Host :

processor    : 0
vendor_id    : GenuineIntel
cpu family    : 6
model        : 45
model name    : Intel(R) Xeon(R) CPU E5-2620 0 @ 2.00GHz
stepping    : 7
microcode    : 0x710
cpu MHz        : 1200.000
cache size    : 15360 KB
physical id    : 0
siblings    : 12
core id        : 0
cpu cores    : 6
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
pdpe1gb 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 pcid dca 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
bogomips    : 3990.17
clflush size    : 64
cache_alignment    : 64
address sizes    : 46 bits physical, 48 bits virtual
power management:


Thanks
Aki


On Wed, Jan 25, 2017 at 2:36 PM, Jiri Denemark <jdenemar at redhat.com> wrote:

> On Tue, Jan 24, 2017 at 16:21:14 +0530, akhilesh rawat wrote:
> > hi,
> >
> > yes we are talking about same host here.
> >
> > You could've just used -cpu host-model-only
> > >> I dont want to host model ( it is working with host model) .
> >
> > AS KVM seems to allow support Haswell with native commands . Does this
> mean
> > in my case KVM is allowing software emulated cpu model.
>
> No, QEMU will just drop the features which are not supported on your
> host. Although there are some rare exceptions, such as x2apic, which can
> be emulated even with KVM.
>
> Anyway, starting QEMU directly should print several warnings about
> features which are dropped. And when you start QEMU with
> -cpu Haswell,enforce it should refuse to start.
>
> > Can libvirt allow  software-emulated for non host model ?  if yes how .
>
> You can bypass the libvirt check for specific features by setting the
> feature policy to "force" (no idea if this can be done with
> virt-install), but QEMU will still do the check itself and either drop
> the features or refuse to start (with enforce) if they cannot be used on
> the host.
>
> Jirka
>
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