OS & Hardware

Which describes paravirtualization?

  1. AThe guest OS is left completely unmodified, and real hardware devices are reproduced exactly
  2. BThe guest OS knows it is virtualized and uses efficient procedures designed for the hypervisor
  3. CMultiple applications run inside one OS without any hypervisor
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Answer: B. The guest OS knows it is virtualized and uses efficient procedures designed for the hypervisor

Emulating a real device in full detail triggers a switch to the hypervisor on every device register access, which is slow. With paravirtualization, the guest OS installs virtualization-aware drivers and uses efficient, virtualization-aware procedures, such as exchanging batched requests through queues in shared memory. It is widely used for virtual disks and network devices. Reproducing devices exactly without modifying the OS is the idea of full virtualization.

  • A. Reproducing real devices without changing the OS is full virtualization.
  • B. Correct. It uses efficient procedures that assume virtualization.
  • C. Running multiple applications in one OS is what ordinary OSes do.
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  1. Which correctly distinguishes containers from virtual machines?
  2. Many OSes map the kernel into part of every process's address space (for example the upper range) and forbid user-mode access through page-table protection bits. What is the main advantage of this layout?
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