How to copy data between guest memory and host

[沈梦姣]

Hi,
I’m adding device for one platform(e.g. mps2), and also writing driver for that 
device on guest os. There is a buffer allocated in qemu where some data will be 
cooked, and driver will update buffer address located in guest memory space to 
qemu device. So the question is how to copy data between the two different 
memory space?

Thanks a lot!