Description of problem: Test win2019 guest booting with different vectors. Guest network works well with vectors 0/2/3/4/5, however network is down when vectors=1. Version-Release number of selected component (if applicable): kernel-4.18.0-67.el8.x86_64 virtio-win-1.9.7-3.el8.noarch qemu-kvm-3.1.0-17.module+el8+2831+8d13a174.x86_64 How reproducible: 10/10 Steps to Reproduce: 1.Boot win2019 guest with queues=4 and vectors=1. qemu prompts errors. /usr/libexec/qemu-kvm -name Win2019 \ -M q35,kernel-irqchip=split -m 4g \ -cpu EPYC,hv_stimer,hv_synic,hv_time,hv_relaxed,hv_vpindex,hv_spinlocks=0xfff,hv_vapic,hv_reset,hv_crash \ -device intel-iommu,intremap=true,caching-mode=true \ -smp 4,sockets=1,cores=4,threads=1 \ -device pcie-root-port,id=root.1,chassis=1 \ -device pcie-root-port,id=root.2,chassis=2 \ -blockdev driver=file,cache.direct=off,cache.no-flush=on,filename=/home/win2019.qcow2,node-name=my_file \ -blockdev driver=qcow2,node-name=my,file=my_file \ -device virtio-blk-pci,drive=my,id=virtio-blk0,bus=root.1 \ -drive id=drive_cd1,if=none,snapshot=off,aio=native,cache=none,media=cdrom,file=/home/en_windows_server_2019_x64_dvd_4cb967d8.iso \ -device ide-cd,id=cd1,drive=drive_cd1,bus=ide.0,unit=0 \ -drive id=drive_winutils,if=none,snapshot=off,aio=native,cache=none,media=cdrom,file=/usr/share/virtio-win/virtio-win-1.9.7.iso \ -device ide-cd,id=winutils,drive=drive_winutils,bus=ide.1,unit=0 \ -vnc :3 \ -vga qxl \ -monitor stdio \ -usb -device usb-tablet \ -boot menu=on \ -netdev tap,id=hostnet1,vhost=on,queues=4 \ -device virtio-net-pci,indirect_desc=off,netdev=hostnet1,id=net1,mac=18:66:da:5f:d1:02,bus=root.2,vectors=1,mq=on \ (qemu) qemu-kvm: unable to start vhost net: 14: falling back on userspace virtio qemu-kvm: warning: guest updated active QH qemu-kvm: warning: guest updated active QH qemu-kvm: warning: guest updated active QH qemu-kvm: warning: guest updated active QH qemu-kvm: warning: guest updated active QH 2.Check guest Network status-->Not connected Actual results: Network is down. Expected results: Network is up. Additional info: 1. It's possibly same issue with issue in rhel7.6: Bug 1608226 - [virtual-network][mq] prompt warning "qemu-kvm: unable to start vhost net: 14: falling back on userspace virtio" when boot with win8+ guests with multi-queue
This is a virtio-win bug. And it's duplicate with Bug 1666940. *** This bug has been marked as a duplicate of bug 1666940 ***
It does not seem this bug is duplicate of Bug 1666940 (1666940 is related to virtio-win-prewhql 162/163) This BZ is open for virtio-win 160 (virtio-win-1.9.7-3.el8), with netkvm build 160 the network shall function with single vector (just with not optimal performance). "falling back on userspace virtio" - does not indicate any fatal problem, just a fallback to qemu networking instead of vhost. Please verify the problem happens with netkvm build 160 (netkvm.inf and netkvm.sys has version .16400)
(netkvm.inf and netkvm.sys has version .16000)
(In reply to ybendito from comment #3) > (netkvm.inf and netkvm.sys has version .16000) But for ws2019, we use build 162 in virtio-win-1.9.7-3.el8.noarch, other guests are build 160.
(In reply to Yu Wang from comment #4) > (In reply to ybendito from comment #3) > > (netkvm.inf and netkvm.sys has version .16000) > > But for ws2019, we use build 162 in virtio-win-1.9.7-3.el8.noarch, other > guests are build 160. OK, sorry, I've missed this point. So, yes, the build 162 is buggy. Latest builds (165+) shall fix the problem.