[qemu] VNC鼠标不同步

启用qemu的VNC远程控制之后，默认鼠标指针总是跟客户端指针运动不同步，网上教的是加上-usbdevice tablet参数即可搞定，但此参数在新版qemu使用时被警告已被弃用，看了文档https://qemu.weilnetz.de/doc/qemu-doc.html#g_t_002dusbdevice-_0028since-2_002e10_002e0_0029，新的参数应该是

-machine usb=on -device usb-tablet，文档中的原文解释是：

B.2.15 -usbdevice (since 2.10.0)

The “-usbdevice DEV” argument is now a synonym for setting the “-device usb-DEV” argument instead. The deprecated syntax would automatically enable USB support on the machine type. If using the new syntax, USB support must be explicitly enabled via the “-machine usb=on” argument.

其中“-machine usb=on” 用于开启USB总线，

“-device usb-tablet”用于指定鼠标使用绝对坐标，原文是：

Pointer device that uses absolute coordinates (like a touchscreen). This means QEMU is able to report the mouse position without having to grab the mouse. Also overrides the PS/2 mouse emulation when activated.