1. CS533 Concepts of Operating Systems Class 7 Virtualization and Exokernels

2. CS533 - Concepts of Operating Systems 2 Questions  Why would a guest OS need real, virtual and wall clock time abstractions?  Why might a guest OS need machine addresses instead of just virtual physical addresses?  What kind of virtualization is needed for application binary compatibility?  Why isn’t an emulation library approach equivalent to a virtual machine approach?

3. CS533 - Concepts of Operating Systems 3 Questions  Why is para-virtualization needed for high performance on architectures such as x86?  Why is it harder to virtualize CPUs with hardware specified page tables than software managed TLBs?  Why do tagged TLBs help?  Xen is not transparent to a guest OS. In what ways can the OS distinguish execution on Xen from execution on bare hardware?

4. CS533 - Concepts of Operating Systems 4 Questions  What is the difference between … o full virtualization and para virtualization? o virtualizing and multiplexing resources?  Are Disco and Xen micro-kernels? o Do they support modularization of operating system code? o Do micro-kernels do virtualization? o Does Xen use colocation?  How do VM monitors/hypervisors ensure safety? o Is virtualization a sandboxing technique?

5. CS533 - Concepts of Operating Systems 5 Questions  At what granularity do VM monitors support multitasking? o How does it differ from conventional multitasking? o How do virtualized CPUs differ from threads/processes?  Does virtualization hide any critical characteristics of the real hardware?  Why is it difficult to virtualize the x86? o What aspect of the x86 helps virtualization?  What hardware support would be nice to have?

6. CS533 - Concepts of Operating Systems 6 Questions  What is the difference between virtualization and secure multiplexing? o What do Exokernel and Disco have in common? o What do Exokernel and Xen have in common? o Do Xen or Disco do secure multiplexing? o Does Exokernel create virtual machines?  Is Exokernel a micro-kernel? o What abstractions does it support?

7. CS533 - Concepts of Operating Systems 7 Questions  What is a "process" in the Exokernel?  Does the Exokernel "paravirtualize" privileged instructions?  How are address translations and physical memory managed in the Exokernel?  How does Exokernel’s visible revocation relate to scheduler activations? o How does it differ from Xen and Disco in this respect?  How does PCT relate to LRPC? o What is the difference between synchronous and asynchronous PCT?

8. CS533 - Concepts of Operating Systems 8 Questions  How does Exokernel use hardware support to improve performance?  How are "software caches" used to improve performance?  How is "downloaded code" used to improve performance? o How does this relate to Sandboxing? o How does this relate to SPIN? o How does this relate to Specialization?  What do hardware support, software caches and downloaded code have in common?