Re: [Xen-users] Is Xen really a Type 1 Hypervisor?

[eva <evammg@xxxxxxxxx>]

On 16 April 2012 13:57, John McDermott CIV <john.mcdermott@xxxxxxxxxxxx> wrote:
>
>
> The main Wikipedia article is not clear. Type 1 and Type 2 are NOT defined by 
> what is "running" on what. All of the software "runs" on the hardware. The 
> meaning of Type 1 and Type 2 depends on what is called a _sensitive 
> instruction_: any instruction in the hardware ISA that could interfere with 
> or screw up the hypervisor. A hypervisor needs to control and manage the 
> execution of all sensitive instructions, so it needs to know when a guest is 
> attempting to execute a sensitive instruction, and take control. Otherwise, a 
> guest could misuse a sensitive instruction. An example of a sensitive 
> instruction on the x86 is int n.
>
> A Type 1 hypervisor detects sensitive instructions for itself but a Type 2 
> hypervisor relies on some other software (typically a conventional OS)to 
> detect them and then pass the notification on to the hypervisor.
>
> Xen is Type 1; you can look at the source code to confirm this, though you 
> will need to understand how to read AT&T assembler syntax.
>
> Sincerely,
>
> John
>
>

John,

 Clear enough :) Thank you.

Casey,

Could you explain this

"I tried ESXi, and switched to Xen specifically because the tiny
built-in control OS doesn't support a myriad of consumer drivers,
something that having a Linux control guest fixes."

in a different way?

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