Bug 1824126

Summary:	[virtual-network][mq][Windows vm][RHEL.8.2 slow train]qemu output error info: qemu-kvm: unable to start vhost net: 14: falling back on userspace virtio
Product:	Red Hat Enterprise Linux 8	Reporter:	Peixiu Hou <phou>
Component:	qemu-kvm	Assignee:	ybendito
qemu-kvm sub component:	Networking	QA Contact:	Lei Yang <leiyang>
Status:	CLOSED WONTFIX	Docs Contact:
Severity:	high
Priority:	high	CC:	aadam, ailan, chayang, ghammer, jasowang, jinzhao, jomurphy, juzhang, leiyang, lijin, lmiksik, lulu, maxime.coquelin, mjankula, mtessun, pezhang, phou, virt-bugs, virt-maint, wyu, ybendito, yvugenfi
Version:	8.2	Keywords:	Triaged
Target Milestone:	rc
Target Release:	8.0
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:
Fixed In Version:		Doc Type:	If docs needed, set a value
Doc Text:		Story Points:	---
Clone Of:	1702608	Environment:
Last Closed:	2021-07-01 08:01:38 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:	1608226, 1702608
Bug Blocks:	1649160

Comment 7 Lei Yang 2021-01-12 07:16:12 UTC

Hi Yuri

I reproduced this bug on RHEL8.2 slow train.
Test Version:
qemu-kvm-2.12.0-99.module+el8.2.0+5827+8c39933c.x86_64
kernel-4.18.0-193.el8.x86_64

How reproducible:
100%

==steps
1.queues number smaller than CPUs number, qemu without output.
-smp 8  \
-device virtio-net-pci,mac=9a:89:b9:bc:88:b2,id=idyhQr7l,netdev=idNVyWKH,mq=on,vectors=10,bus=pcie-root-port-3,addr=0x0  \
-netdev tap,id=idNVyWKH,vhost=on,queues=4 \

2.queues number equal to CPUs number, qemu output error info.
-smp 8  \
-device virtio-net-pci,mac=9a:89:b9:bc:88:b2,id=idyhQr7l,netdev=idNVyWKH,mq=on,vectors=18,bus=pcie-root-port-3,addr=0x0  \
-netdev tap,id=idNVyWKH,vhost=on,queues=8 \

(qemu) qemu-kvm: unable to start vhost net: 14: falling back on userspace virtio
qemu-kvm: unable to start vhost net: 14: falling back on userspace virtio

3.queues number large than CPUs number, qemu output error info.
-smp 8  \
-device virtio-net-pci,mac=9a:89:b9:bc:88:b2,id=idyhQr7l,netdev=idNVyWKH,mq=on,vectors=26,bus=pcie-root-port-3,addr=0x0  \
-netdev tap,id=idNVyWKH,vhost=on,queues=12 \

(qemu) qemu-kvm: unable to start vhost net: 14: falling back on userspace virtio
qemu-kvm: unable to start vhost net: 14: falling back on userspace virtio

Tested on RHEL.8.4 slow train, and now there is no problem. According to comment 5, the problem has not reproduced in RHEL.8.3 slow train. Can you help to check it? Has this problem been resolved on slow trains? If it is fixed, we should change the status of this bug.

Test Version on RHEL.8.4 slow train:
kernel-4.18.0-270.el8.x86_64
qemu-kvm-4.2.0-40.module+el8.4.0+9278+dd53883d.x86_64

Best Regards
Lei Yang

Comment 13 Lei Yang 2021-04-01 08:02:15 UTC

Hi Martin

According to Comments 11,12. Is this problem worth fixing on RHEL8.2.z? If it doesn’t need to be fixed on RHEL8.2.z, can I close the bug as "WONTFIX"? Thanks in advance.

Best Regards
Lei

Comment 14 Lei Yang 2021-06-18 02:39:17 UTC

Hi Martin

Could you please help check the Comment 11,12,13 and comment at your earliest convenience? Thanks in advance!

Best Regards
Lei