[Qemu-devel] question about usb passthrough migration

[linzhecheng]

Hi, Gerd
I'm still trying to realize local live-migration with usb passthrough devices  
for purpose of upgrading qemu.
I've made sure that source and target vms will not access host usb devices at 
the same time.
But when I test USB flash disk copying files during live-migration stage, I 
encounter a probabilistic problem: copying task may stuck for a while.
This problem happened just after source vm stoping and target vm starting to 
run, which caused by the long time pending transfer.
In other words, target vm submit the first bulk transfer may not trigger 
callback function. I cannot figure out whether it is a usb driver's bug.
Could you give me some advice or whether you have met the same problem before?