[Xen-devel] On x86_64 Xen Implementation

[BVK Chaitanya <bayapuneni_chaitanya@xxxxxxxxxxxx>]

Hi,

Xen 3.0 inteface manual says:

On 64-bit systems it is not possible to protect the hypervisor from 
untrusted guest code running in rings 1 and 2. Guests are therefore 
restricted to run in ring 3 only. The guest kernel is protected from its 
applications by context switching between the kernel and currently 
running application.
Can anybody explain (or provide me pointers) to what x86_64 features 
make protecting hypervisor from untrusted guest (kernels) impossible? 
Is x86_64 (by-design) makes x86's 4 rings feature obsolete?
thanks,
--
bvk-chaitanya

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