[Qemu-discuss] VM boot failed sometimes if using vhost-user-blk with spdk

[wuzhouhui]

I'm using following command line to start VM (The /var/tmp/vhost.0 connected to 
a 
malloc bdev (16 MB ) created by SPDK):
  /home/wuzhouhui/qemu-2.12.1/x86_64-softmmu/qemu-system-x86_64 \
          -name guest=wzh,debug-threads=on \
          -machine pc-i440fx-2.12,accel=kvm,usb=off \
          -cpu host \
          -m 4096 \
          -object 
memory-backend-file,id=mem0,size=4096M,mem-path=/dev/hugepages,share=on \
          -numa node,memdev=mem0 \
          -realtime mlock=off \
          -smp 2,sockets=2,cores=1,threads=1 \
          -uuid a84e96e6-2c53-408d-986b-c709bc6a0e51 \
          -no-user-config \
          -nodefaults \
          -rtc base=utc,driftfix=slew \
          -global kvm-pit.lost_tick_policy=delay \
          -no-shutdown \
          -boot strict=on \
          -device piix3-usb-uhci,id=usb,bus=pci.0,addr=0x1.0x2 \
          -device ahci,id=sata0,bus=pci.0,addr=0x4 \
          -drive 
file=/home/wuzhouhui/wzh.qcow2,format=qcow2,if=none,id=drive-virtio-disk0,cache=none
 \
          -device 
virtio-blk-pci,scsi=off,bus=pci.0,addr=0x3,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=0
 \ 
          -device usb-tablet,id=input0,bus=usb.0,port=1 \
          -k en-us \
          -device cirrus-vga,id=video0,bus=pci.0,addr=0x2 \
          -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x6 -msg 
timestamp=on \
          -vnc :9 \
          -chardev socket,id=char0,path=/var/tmp/vhost.0 \
          -device vhost-user-blk-pci,id=blk0,chardev=char0,num-queues=4 \

But most of the time, VM boot failed with following message in vnc screen:
  Warning: /dev/disk/by-uuid/e0dcaf0c-bc23-4df6-b2cd-d40aa1bbb0b5 does not exist

  Generating "/run/initramfs/rdsosreport.txt"

  Entering emergency mode. Exit the shell to continue.
  Type "journalctl" to view system logs.
  You might want to save "/run/initramfs/rdsosreport.txt" to a USB stick or 
/boot
  after mounting them and attach it to a bug report.

There is some message from /run/initramfs/rdsosreport.txt:
  ...
  system-udevd[196]: symlink '../../vdb' 
'/dev/disk/by-id/virtio-Malloc.tmp-b253:16' failed: Not a directory
  ...

I checked /dev/disk, it should be a directory, but it is a symlink now:
  :/# ls -l /dev/disk
  lrwxrwxrwx 1 root 0 3 Oct 30 03:08 /dev/disk -> vdb

If I just remove:
  -chardev socket,id=char0,path=/var/tmp/vhost.0 \
  -device vhost-user-blk-pci,id=blk0,chardev=char0,num-queues=4 \
The VM will boot normally.

Does anyone have encountered similar issue like this?

Host OS:  CentOS 7.3, with kernel 3.10.0-862.11.6.el7.x86_64
Guest OS: CentOS 7.5
Qemu: 2.12.1
SPDK: f0cb7b871e in master