[Qemu-devel] virtfs fails after migration

[Malte Starostik]

Hello,

 

trying to get migration work on a setup with several libvirt based hosts, I'm struggling with those VMs that use virtfs shares.

I remember that in previous versions of qemu, the attempt to migrate those lead to chaos and mayhem, while now a *mounted* virtfs simply blocks migration. Fine so far, none of the virtfs shares we use need to be mounted all the time. However, when I unmount and then migrate (whether to a different host or just save/restore), the virtfs can't be mounted anymore.

mount fails with "no such device", and in dmesg I get:

 

9pnet_virtio: no channels available

 

The same thing applies to several combinations, the most up to date one is with host and guest both running a 3.8.13 kernel and qemu 1.4.0.

 

qemu command line:

 

/usr/bin/qemu-system-x86_64 -machine accel=kvm -name test01,process=qemu:test01 -S -M pc-1.2 -m 4096 -smp 1,sockets=1,cores=1,threads=1 -uuid 9d7f74e7-4a90-fbd1-796d-e23357931e80 -no-user-config -nodefaults -chardev socket,id=charmonitor,path=/var/lib/libvirt/qemu/test01.monitor,server,nowait -mon chardev=charmonitor,id=monitor,mode=control -rtc base=utc -no-shutdown -kernel /var/lib/libvirt/images/boot/vmlinuz-3.8.13-gentoo -initrd /var/lib/libvirt/images/boot/initramfs-3.8.13-gentoo.img -append root=UUID=0ccbddca-dc76-4965-95cc-c16956d2670d quiet -device piix3-usb-uhci,id=usb,bus=pci.0,addr=0x1.0x2 -device virtio-serial-pci,id=virtio-serial0,bus=pci.0,addr=0x4 -drive file=/dev/vg-vms/test01,if=none,id=drive-virtio-disk0,format=raw -device virtio-blk-pci,scsi=off,bus=pci.0,addr=0x5,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=1 -fsdev local,security_model=passthrough,id=fsdev-fs0,path=/mnt/portage,readonly -device virtio-9p-pci,id=fs0,fsdev=fsdev-fs0,mount_tag=portage,bus=pci.0,addr=0x7 -netdev tap,fd=20,id=hostnet0,vhost=on,vhostfd=21 -device virtio-net-pci,netdev=hostnet0,id=net0,mac=52:54:00:2b:26:e1,bus=pci.0,addr=0x3 -chardev pty,id=charserial0 -device isa-serial,chardev=charserial0,id=serial0 -chardev spicevmc,id=charchannel0,name=vdagent -device virtserialport,bus=virtio-serial0.0,nr=1,chardev=charchannel0,id=channel0,name=com.redhat.spice.0 -spice port=5900,addr=127.0.0.1,disable-ticketing,seamless-migration=on -vga qxl -global qxl-vga.ram_size=67108864 -global qxl-vga.vram_size=67108864 -incoming fd:18 -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x6

 

Need to reboot the guest for it to work again. Removing the 9p and 9pnet-virtio modules won't do. Is there any known fix or workaround?

 

Kind regards,

Malte