what's the difference between usermode and kernelmode

[devtinoimao]

so I don't really know the difference however I read once in How Linux works (part 2 I think), is that the linux kernel has a space , one for the system and base of the kernel (kernelmode space I think) (my brain is cooked) and another space for user apps and the desktop, and mixing both spaces causes severe instability and crashes (well that's what I know atleast), so I'm just very confused in this

[nooodles2023]

For both real device and virtual device, we can't access it directly in a normal application program. The only way to use device is using driver installed on device. The driver is in kernel space, it provides interface for program in user space.

[nooodles2023]

In this project, the guest app loads opengl32.dll. Opengl operations will be transmited to MvisorVGPU.dll which translate them to virgl commands and deliver them to kernelmode driver