Write a 0xVALUE to a model-specific register at address 0xADDR.
Please note that on SMP systems, writing to a MSR that has a scope per hardware thread, implies that the value that is written only applies to the particular cpu/core/thread that runs the command.
Also, if you specify a reserved or unimplemented MSR address, it will cause a general protection exception (which is not currently being handled) and the system will reboot.
Note: The command is not allowed when lockdown is enforced (see Lockdown). This is done to prevent subverting various security mechanisms.