[Xen-devel] how to check for already existing hypervisor?

[palutke.ralph@xxxxxx]

Hi guys, 

let me shortly introduce myself. I'm a student and recently work on my bachelor 
thesis. My goal is to write a little hypervisor.
I'm not quite sure if this is the right mailing list, but i guess you'll gonna 
tell me.
i have two quick questions:

1. before i can use the vmxon instruction i do have to set vmxe flag in cr4 
register. but what if some hypervisor is already running? is there a way to 
check 
if one is running??

2. before i set the vmxe bit in cr4, i check if it is already enabled. i do 
this while my module gets loaded. but i observed a strange thing. sometimes
the vmxe bit seems to be set while the other time it isn't. do you have any 
explanation for that behaviour? do i have to check if the bit is set before 
actually setting it? I've looked at a few hypervisor projects and it seems that 
no one does it. my primary thought was, if the bit is set a hypervisor is 
running, 
but i don't think that's true anymore. so do i need the check?

greetings 

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