>>> On 2010/08/15 at 14:19, Tapas Mishra <mightydreams@xxxxxxxxx> 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?
I'm not all that familiar with the internals of Xen, but I think the high-level
answer to your question is, it depends. It depends on what type of domU you're
running. Paravirtualized domUs are aware that they are virtualized and that
they do not have ring 0 access, so I'm guessing they do not attempt to execute
instructions in ring 0 without passing it through to the hypervisor, which
brokers those requests. HVM domUs, on the other hand, are full machines (more
along the lines of how VMware does virtualization) that can run an unmodified
kernel. So, kernels in HVM domUs attempt to access ring 0 resources, which
must then be translated by the HVM and passed on to the hypervisor.
That's my understanding of how it works...
-Nick
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