vmlaunch

Simple Driver code for vmlaunch The idea behind the driver is to demonstrate a real example of how to initialize the Virtual Machine Control Structure(VMCS) and to use Intel VT instructions to launch a virtual machine. The driver launches a guest (virtual machine) with vmlaunch, executes one instruction(that causes a vmexit) and then returns to the host. For the vmlaunch instruction to execute successfully, a lot of cpu state (host and guest state) needs to be initialized all of which is done by this driver. The driver also takes a simple approach in setting up the guest state by making it mirror the host state. This makes the design much simpler - for instance the guest does not need its own CR3, it shares it with the host. Inline assembly is used generously throughout the driver.

One possible concern: The VMCS does not have a host state field for LDTs. After a vmexit, the processor loads the LDT selector to null. If a non-zero ldt selector is required before the module exits then the code after vmexit may require a lldt <sel_value> to establish the ldtr to a good state.