guest cpu not exact as host

[nike]

sir,
i have configured a guest on host using Virtual Machine Manager of centos 7.9 server version . the guest is running fine in all aspect . But when i am checking guest pc's cpu model name using "lscpu " result is not as HOST server below the result of both host and guest ...please any help

host cpu model is showing Model name: Intel(R) Xeon(R) Silver 4210R CPU @ 2.40GHz

guest cpu model name Model name: Intel Xeon Processor (Skylake, IBRS)

why it is different ? and how it will be configured to show as host



HOST server
[root@XXXX-HOST]# lscpu
Architecture: x86_64
CPU op-mode(s): 32-bit, 64-bit
Byte Order: Little Endian
CPU(s): 20
On-line CPU(s) list: 0-19
Thread(s) per core: 2
Core(s) per socket: 10
Socket(s): 1
NUMA node(s): 1
Vendor ID: GenuineIntel
CPU family: 6
Model: 85
Model name: Intel(R) Xeon(R) Silver 4210R CPU @ 2.40GHz
Stepping: 7
CPU MHz: 1000.048
CPU max MHz: 3200.0000
CPU min MHz: 1000.0000
BogoMIPS: 4800.00
Virtualization: VT-x
L1d cache: 32K
L1i cache: 32K
L2 cache: 1024K
L3 cache: 14080K
NUMA node0 CPU(s): 0-19
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 art arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc aperfmperf eagerfpu pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 sdbg fma cx16 xtpr pdcm pcid dca sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand lahf_lm abm 3dnowprefetch epb cat_l3 cdp_l3 invpcid_single intel_ppin ssbd mba rsb_ctxsw ibrs ibpb stibp ibrs_enhanced tpr_shadow vnmi flexpriority ept vpid fsgsbase tsc_adjust bmi1 hle avx2 smep bmi2 erms invpcid rtm cqm mpx rdt_a avx512f avx512dq rdseed adx smap clflushopt clwb intel_pt avx512cd avx512bw avx512vl xsaveopt xsavec xgetbv1 cqm_llc cqm_occup_llc cqm_mbm_total cqm_mbm_local dtherm ida arat pln pts hwp hwp_act_window hwp_pkg_req pku ospke avx512_vnni md_clear spec_ctrl intel_stibp flush_l1d arch_capabilities


GUEST PC
[root@XXX-VM ~]# lscpu
Architecture: x86_64
CPU op-mode(s): 32-bit, 64-bit
Byte Order: Little Endian
CPU(s): 3
On-line CPU(s) list: 0-2
Thread(s) per core: 1
Core(s) per socket: 1
Socket(s): 3
NUMA node(s): 1
Vendor ID: GenuineIntel
CPU family: 6
Model: 85
Model name: Intel Xeon Processor (Skylake, IBRS)
Stepping: 4
CPU MHz: 2394.374
BogoMIPS: 4788.74
Hypervisor vendor: KVM
Virtualization type: full
L1d cache: 32K
L1i cache: 32K
L2 cache: 4096K
NUMA node0 CPU(s): 0-2
Flags: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 syscall nx pdpe1gb rdtscp lm constant_tsc rep_good nopl eagerfpu pni pclmulqdq ssse3 fma cx16 pcid sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand hypervisor lahf_lm abm 3dnowprefetch invpcid_single ssbd ibrs ibpb fsgsbase bmi1 hle avx2 smep bmi2 erms invpcid rtm mpx avx512f avx512dq rdseed adx smap clwb avx512cd avx512bw avx512vl xsaveopt xsavec xgetbv1 md_clear spec_ctrl



and result of lsmod on my server is
[root@XXX-HOSTI admin]# lsmod | grep kvm
kvm_intel 188793 5
kvm 653928 1 kvm_intel
irqbypass 13503 3 kvm

[jlehtone]

Look at the details of the VM in virt-manager. The "CPUs" section should include Configuration, Model.

[TrevorH]

The bottom line is that it doesn't need to match anyway.

[jlehtone]

Indeed. The features exposed to the VM can be a subset of the features of the physical CPU.


Why would one do that? I can think of two examples:
1. New feature in CPU has a vulnerability. One can mitigate risk by not giving the VMs access to that feature.
2. Multiple heterogenous hosts. It is easier to migrate VM to another host if it uses only features present in all hosts.

[TrevorH]

Also there are features listed under the real cpu that are not available to the guest.

[nike]

Look at the details of the VM in virt-manager. The "CPUs" section should include Configuration, Model.

yes, i saw that option and in CPU configuration i selected "copy host cpu configuration and model as host-model" . But result is that i told .

[nike]

Also there are features listed under the real cpu that are not available to the guest.

Sir,
Somehow i cannot have to show my guest pc's cpu model as host . Or are there any option to add this host cpu model with virt-manager so that it will be shown on guest pc ? I have seen it different cloud vm. So i tried to do that but failed.

Here is below that cloud vm

-bash-4.2$ lscpu
Architecture: x86_64
CPU op-mode(s): 32-bit, 64-bit
Byte Order: Little Endian
CPU(s): 5
On-line CPU(s) list: 0-4
Thread(s) per core: 1
Core(s) per socket: 1
Socket(s): 5
NUMA node(s): 1
Vendor ID: GenuineIntel
CPU family: 6
Model: 85
Model name: Intel(R) Xeon(R) Silver 4114 CPU @ 2.20GHz
Stepping: 4
CPU MHz: 2194.842
BogoMIPS: 4389.68
Hypervisor vendor: KVM
Virtualization type: full
L1d cache: 32K
L1i cache: 32K
L2 cache: 1024K
L3 cache: 14080K
NUMA node0 CPU(s): 0-4
Flags: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ss syscall nx pdpe1gb rdtscp lm constant_tsc arch_perfmon rep_good nopl xtopology eagerfpu pni pclmulqdq ssse3 fma cx16 pcid sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand hypervisor lahf_lm abm 3dnowprefetch invpcid_single ssbd rsb_ctxsw ibrs ibpb stibp fsgsbase tsc_adjust bmi1 hle avx2 smep bmi2 erms invpcid rtm mpx avx512f avx512dq rdseed adx smap clflushopt clwb avx512cd avx512bw avx512vl xsaveopt xsavec xgetbv1 arat pku ospke md_clear spec_ctrl intel_stibp arch_capabilities

[jlehtone]

yes, i saw that option and in CPU configuration i selected "copy host cpu configuration and model as host-model" . But result is that i told .

Did you shut down and restart the VM after that?

[nike]

yes, i saw that option and in CPU configuration i selected "copy host cpu configuration and model as host-model" . But result is that i told .

Did you shut down and restart the VM after that?

many timesi have done it

[nike]

i have done it at last . actually i have to define cpu mode in bash script