Error connecting to graphical console: Error initializing USB support: Other errors[-99]

CentOS 7上使用virt-manager创建新虚拟机时出现下面错误：

Error connecting to graphical console: Error initializing USB support: Other errors[-99]

造成上面问题的原因是虚拟机的显示协议不匹配，设置一下现实协议为VNC即可。

也可以通过以下方法解决：

I added a usb controller to the virtual machine in vmware that I was using KVM and the console connected.

参考链接：

http://askubuntu.com/questions/641285/error-installing-ubuntu-14-04-in-kvm

http://unix.stackexchange.com/questions/226884/error-initializing-usb-support-other-error-99