Which of the following items belong to the working mode of CPU in full virtualization? (Multiple choice)

Question

Options

• ABinary rewriting
• BPure software simulation
• CModify the kernel
• DTrapped and simulated

• A
  71% (15)
• C
  29% (6)

Explanation

Full virtualization allows unmodified guest operating systems to run by intercepting and handling privileged instructions through several techniques. Binary rewriting (A) rewrites privileged instructions in guest code at runtime before execution (used by VMware), pure software simulation (B) emulates hardware entirely in software so the guest OS never touches real hardware directly, and trap-and-emulate (D) causes privileged instructions to trap to the hypervisor, which then safely simulates their effect - all three operate without touching the guest OS itself.

Option C (modify the kernel) is wrong because kernel modification is the defining characteristic of para-virtualization (e.g., Xen), not full virtualization. Full virtualization's entire value proposition is that the guest OS runs completely unmodified.

Memory tip: Think of "full" as meaning the guest is fully unmodified - if a technique requires touching the guest OS kernel (C), it breaks the "full" contract and belongs to para-virtualization instead.

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