Multi-queue vhost-user fails to reconnect with qemu version >=4.2
This bug has been copied automatically from: https://bugs.launchpad.net/qemu/+bug/1888818
Reported by 'xuan' on 2020-07-24 :
Test Environment: DPDK version: DPDK v20.08 Other software versions: qemu4.2.0, qemu5.0.0. OS: Linux 4.15.0-20-generic Compiler: gcc (Ubuntu 7.3.0-16ubuntu3) 8.4.0 Hardware platform: Purley. Test Setup Steps to reproduce List the steps to reproduce the issue. Test flow ========= 1. Launch vhost-user testpmd as port0 with 2 queues: ./x86_64-native-linuxapp-gcc/app/testpmd -l 2-4 -n 4 \ --file-prefix=vhost --vdev 'net_vhost0,iface=vhost- net,queues=2,client=1' -- -i --txd=1024 --rxd=1024 --txq=2 --rxq=2 testpmd>start 3. Launch qemu with virtio-net: taskset -c 13 \ qemu-system-x86_64 -name us-vhost-vm1 \ -cpu host -enable-kvm -m 2048 -object memory-backend- file,id=mem,size=2048M,mem-path=/mnt/huge,share=on \ -numa node,memdev=mem \ -mem-prealloc -monitor unix:/tmp/vm2_monitor.sock,server,nowait -netdev user,id=yinan,hostfwd=tcp:127.0.0.1:6005-:22 -device e1000,netdev=yinan \ -smp cores=1,sockets=1 -drive file=/home/osimg/ubuntu16.img \ -chardev socket,id=char0,path=./vhost-net,server \ -netdev type=vhost-user,id=mynet1,chardev=char0,vhostforce,queues=2 \ -device virtio-net- pci,mac=52:54:00:00:00:01,netdev=mynet1,mrg_rxbuf=on,csum=on,gso=on,host_tso4=on,guest_tso4=on,mq=on,vectors=15 \ -vnc :10 -daemonize 6. Quit testpmd and restart vhost-user : testpmd>quit ./x86_64-native-linuxapp-gcc/app/testpmd -l 2-4 -n 4 \ --file-prefix=vhost --vdev 'net_vhost0,iface=vhost- net,queues=2,client=1' -- -i --txd=1024 --rxd=1024 --txq=2 --rxq=2 Expected Result: After the vhost-user is killed then re-launched, the virtio-net can connect back to vhost-user again. Actual Result: Vhost-user relaunch failed with continous log printed"VHOST_CONFIG: Processing VHOST_USER_SET_FEATURES failed. Analysis: This is a regression bug, bad commit: c6beefd674f When vhost-user quits, QEMU doesnot save acked features for each virtio- net after vhost-user quits. When vhost-user reconnects to QEMU, QEMU sends two different features(one is the true acked feature while the another is 0x40000000) to vhost-user successively which causing vhost-user exits abnormally.