how to check for already existing hypervisor?

how to check for already existing hypervisor?

[palutke.ralph]

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 

how to check for already existing hypervisor?

[palutke.ralph]

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 

Re: how to check for already existing hypervisor?

[Tim Deegan]

At 02:44 +0200 on 21 Jun (1340246688), palutke.ralph@gmx.de wrote:
> 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??

A lot of hypervisors report their presence in CPUID leaves - have a look
at xen-detect in the tools/ directory for how to spot Xen. 


Tim.