Hello, I set this bug to invalid as it looks like it is not a nova bug.
Feel free to set this bug to new if you disagree.
** Changed in: nova
Status: Confirmed => Invalid
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https://bugs.launchpad.net/bugs/1998032
Title:
AMD EPYC Milan CPU, libvirt/qemu incorrect L3 cache displayed using
cpu-passthrough flag
Status in OpenStack Compute (nova):
Invalid
Bug description:
Description
===========
Train version of Openstack, deployed via Openstack-Ansible on Ubuntu
18.04. Deployment of a single guest VM on a AMD EPYC 7713P 64-Core
Proc hypervisor.
Problem,
The cpu output on the guest VM is not showing the correct L3 cache
information, only consuming half of the hypervisors respective L3
cache. This is not ideal for clients performance testing requirements
and L3 cache utilization. Using nova/libvirt flag of cpu_mode = host-
passthrough has been the most consistent for cpu performance then any
of the other cpu_mode flags.
Questions:
1. Is there a possible known bug in any bionic versions of libvirt/qemu that
may casue this discrepency?
2. Any missing cpu flags that could cause this issue, that may need to be
added to the libvirt domain, via a nova config override?
Expected result
===============
lscpu output of guest VM should show L3 cache value of 32768K
Actual result
=============
lscpu on guest vm shows L3 cache value of 16384K
Environment
===========
OS details:
Distributor ID: Ubuntu
Description: Ubuntu 18.04.6 LTS
Release: 18.04
Codename: bionic
Openstack Version:
DISTRIB_ID="OSA"
DISTRIB_RELEASE="20.2.6"
DISTRIB_CODENAME="Train"
DISTRIB_DESCRIPTION="OpenStack-Ansible"
Hypervisor Libvirt/QEMU versions
qemu-system-x86 1:4.2-3ubuntu6.23~cloud0
libvirt-daemon 6.0.0-0ubuntu8.16~cloud0
Logs & Configs
==============
hypervisor nova libvirt config
[libvirt]
inject_partition = -2
inject_password = False
inject_key = False
virt_type = kvm
cpu_mode = host-passthrough
live_migration_uri =
"qemu+ssh://nova@%s/system?no_verify=1&keyfile=/var/lib/nova/.ssh/id_rsa"
live_migration_tunnelled = True
hw_disk_discard = ignore
disk_cachemodes = file=directsync
**Just a note, reserved one core for the underlying hypervisor and pinned the
other 63 cores to the guest VM**
Hypervisor CPU output
Architecture: x86_64
CPU op-mode(s): 32-bit, 64-bit
Byte Order: Little Endian
CPU(s): 64
On-line CPU(s) list: 0-63
Thread(s) per core: 1
Core(s) per socket: 64
Socket(s): 1
NUMA node(s): 1
Vendor ID: AuthenticAMD
CPU family: 25
Model: 1
Model name: AMD EPYC 7713P 64-Core Processor
Stepping: 1
CPU MHz: 1781.378
CPU max MHz: 2000.0000
CPU min MHz: 1500.0000
BogoMIPS: 4000.20
Virtualization: AMD-V
L1d cache: 32K
L1i cache: 32K
L2 cache: 512K
L3 cache: 32768K
NUMA node0 CPU(s): 0-63
Flags: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca
cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt pdpe1gb
rdtscp lm constant_tsc rep_good nopl nonstop_tsc cpuid extd_apicid aperfmperf
pni pclmulqdq monitor ssse3 fma cx16 pcid sse4_1 sse4_2 movbe popcnt aes xsave
avx f16c rdrand lahf_lm cmp_legacy svm extapic cr8_legacy abm sse4a misalignsse
3dnowprefetch osvw ibs skinit wdt tce topoext perfctr_core perfctr_nb bpext
perfctr_llc mwaitx cpb cat_l3 cdp_l3 invpcid_single hw_pstate ssbd mba ibrs
ibpb stibp vmmcall fsgsbase bmi1 avx2 smep bmi2 invpcid cqm rdt_a rdseed adx
smap clflushopt clwb sha_ni xsaveopt xsavec xgetbv1 xsaves cqm_llc
cqm_occup_llc cqm_mbm_total cqm_mbm_local clzero irperf xsaveerptr wbnoinvd
arat npt lbrv svm_lock nrip_save tsc_scale vmcb_clean flushbyasid decodeassists
pausefilter pfthreshold v_vmsave_vmload vgif umip pku ospke vaes vpclmulqdq
rdpid overflow_recov succor smca
Virtual Machine CPU output using host-passthrough libvirt flag
Architecture: x86_64
CPU op-mode(s): 32-bit, 64-bit
Byte Order: Little Endian
CPU(s): 63
On-line CPU(s) list: 0-62
Thread(s) per core: 1
Core(s) per socket: 63
Socket(s): 1
NUMA node(s): 1
Vendor ID: AuthenticAMD
CPU family: 25
Model: 1
Model name: AMD EPYC 7713P 64-Core Processor
Stepping: 1
CPU MHz: 1999.999
BogoMIPS: 3999.99
Virtualization: AMD-V
Hypervisor vendor: KVM
Virtualization type: full
L1d cache: 64K
L1i cache: 64K
L2 cache: 512K
L3 cache: 16384K
NUMA node0 CPU(s): 0-62
Flags: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge
mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt
pdpe1gb rdtscp lm art rep_good nopl extd_apicid 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 cmp_legacy svm cr8_legacy abm sse4a
misalignsse 3dnowprefetch osvw perfctr_core retpoline_amd ssbd ibrs ibpb stibp
vmmcall fsgsbase tsc_adjust bmi1 avx2 smep bmi2 rdseed adx smap clflushopt clwb
sha_ni xsaveopt xsavec xgetbv1 clzero xsaveerptr arat npt nrip_save umip vaes
vpclmulqdq spec_ctrl intel_stibp arch_capabilities
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