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Bug 1723520

Summary:	TOPOEXT not supported by Opteron_* CPU models
Product:	Red Hat Enterprise Linux Advanced Virtualization	Reporter:	Eduardo Habkost <ehabkost>
Component:	qemu-kvm	Assignee:	Eduardo Habkost <ehabkost>
qemu-kvm sub component:	CPU Models	QA Contact:	liunana <nanliu>
Status:	CLOSED WONTFIX	Docs Contact:
Severity:	unspecified
Priority:	low	CC:	ailan, chayang, jinzhao, juzhang, lhuang, nanliu, virt-maint, yuhuang, zhguo
Version:	8.1	Flags:	knoel: mirror+
Target Milestone:	rc
Target Release:	---
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:
Fixed In Version:		Doc Type:	If docs needed, set a value
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2021-03-15 07:37:00 UTC	Type:	Bug
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:
Bug Blocks:	1615682

Description Eduardo Habkost 2019-06-24 17:26:03 UTC

This bug was initially created as a copy of Bug #1615682

I am copying this bug because: 
It is not fixed upstream yet and requires some clean up in the CPU cache configuration code.  The RHEL-7 bug will likely be closed and this will be fixed in RHEL-8 and RHEL-AV-8 only.


Description of problem:
Guest should get 2 threads per core and all of them should be on-line when booting guest with old amd cpu model + smt

Version-Release number of selected component (if applicable):
qemu-kvm-rhev-2.12.0-10.el7.x86_64
kernel-3.10.0-933.el7.x86_64(host & guest)

How reproducible:
100%

Steps to Reproduce:
1.Boot rhel7.6 guest with cli:
/usr/libexec/qemu-kvm -name rhel7.6 -m 16G -machine pc,accel=kvm \
        -S \
        -cpu Opteron_G3,+topoext,xlevel=0x8000001e,enforce \
        -smp 2,threads=2 \
        -monitor stdio \
        -qmp unix:/tmp/qmp2,server,nowait \
        -device VGA \
        -vnc :0 \
        -serial unix:/tmp/console2,server,nowait \
        -uuid 115e11b2-a869-41b5-91cd-6a32a907be7f \
        -drive file=rhel7.6-20180812.qcow2,if=none,id=drive-scsi-disk0,format=qcow2,cache=none,werror=stop,rerror=stop -device ide-hd,drive=drive-scsi-disk0,id=scsi-disk0 \
        -netdev tap,id=idinWyYY,vhost=on -device virtio-net-pci,mac=2e:39:fa:ff:88:a1,id=idlbq7eA,netdev=idinWyYY \

2.check cpu info inside guest
3.

Actual results:
Guest gets one online cpu, one offline cpu and one thread per core:
# lscpu
lscpu
Architecture:          x86_64
CPU op-mode(s):        32-bit, 64-bit
Byte Order:            Little Endian
CPU(s):                2
On-line CPU(s) list:   0
Off-line CPU(s) list:  1
Thread(s) per core:    1
Core(s) per socket:    1
Socket(s):             1
NUMA node(s):          1
Vendor ID:             AuthenticAMD
CPU family:            16
Model:                 2
Model name:            AMD Opteron 23xx (Gen 3 Class Opteron)
Stepping:              3
CPU MHz:               2096.060
BogoMIPS:              4192.12
Hypervisor vendor:     KVM
Virtualization type:   full
L1d cache:             64K
L1i cache:             64K
L2 cache:              512K
L3 cache:              16384K
NUMA node0 CPU(s):     0
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 lm art rep_good nopl extd_apicid pni cx16 x2apic popcnt hypervisor lahf_lm cmp_legacy abm sse4a misalignsse topoext retpoline_amd ibp_disable vmmcall


Expected results:
Guest should get 2 threads per core and all of them should be on-line

Additional info:

Comment 1 Eduardo Habkost 2019-06-24 17:30:38 UTC

For info on another crash caused by the same issue, see bug 1619166.

Comment 3 Ademar Reis 2020-02-05 22:59:33 UTC

QEMU has been recently split into sub-components and as a one-time operation to avoid breakage of tools, we are setting the QEMU sub-component of this BZ to "General". Please review and change the sub-component if necessary the next time you review this BZ. Thanks

Comment 8 RHEL Program Management 2021-03-15 07:37:00 UTC

After evaluating this issue, there are no plans to address it further or fix it in an upcoming release.  Therefore, it is being closed.  If plans change such that this issue will be fixed in an upcoming release, then the bug can be reopened.

Comment 9 liunana 2021-03-17 06:12:43 UTC

Hi Eduardo,


I still can reproduce this bug now, do we have a plan to fix this?
If so, we can re-open this bug.


Test environments:
   hp-dl585g7-05.lab.eng.pek2.redhat.com
   Model name:          AMD Opteron(tm) Processor 6376
   kernel-4.18.0-297.el8.x86_64
   qemu-kvm-5.2.0-11.module+el8.4.0+10268+62bcbbed.x86_64


Steps:
1. Boot guest with:
    -smp 2,threads=2  \
    -cpu 'Opteron_G3',+topoext,xlevel=0x8000001e,enforce,+kvm_pv_unhalt \

2. check the topology inside the guest.


Results inside guest:
[root@vm-73-220 ~]# lscpu
lscpu
Architecture:        x86_64
CPU op-mode(s):      32-bit, 64-bit
Byte Order:          Little Endian
CPU(s):              2
On-line CPU(s) list: 0,1
Thread(s) per core:  1
Core(s) per socket:  2
Socket(s):           1
NUMA node(s):        1



Best regards
Liu Nana

Comment 10 Eduardo Habkost 2021-04-08 22:20:14 UTC

(In reply to liunana from comment #9)
> Hi Eduardo,
> 
> 
> I still can reproduce this bug now, do we have a plan to fix this?
> If so, we can re-open this bug.

No short term plans to address this, and no customer complaints about it.  We can leave it closed.