Re: [Xen-devel] [SPAM] how does hypervisor isolates DomU from Dom0

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Mon, Aug 16, 2010 at 01:55:25AM +0530, Tapas Mishra wrote:
> I am not clear with the working of hypervisor xen.
> How does an instruction executed by kernel in Ring0 of DomU gets
> mapped or executed by hypervisor and then is excuted in Dom0.
> Is this thing some where on the wiki page?
> 

Xen hypervisor runs in ring0.
Xen PV domUs don't run in ring0, instead they run in ring1.

In case of Xen HVM guests the Xen hypervisor runs in ring -1,
with help of the CPU virtualization extensions (Intel VT / AMD-V), 
so the HVM guest kernel can run in it's own private virtual ring0.

And what do you mean with "then is executed in dom0" ?

Dom0 is another guest VM, but it has some more privileges 
(direct access to the hardware) and responsibilities 
(run management toolstack and provide virtual disks and nics for other guests).

-- Pasi


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