Regd Harware assisted Virtualization

Question

I am trying to understand hardware assisted virtualization for a project with ARM CortexA8 and using the ARM Trustzone feature. I am new to this topic therefore I started with Wiki entries to understand more.

Wikipedia explains hardware assisted virtialization and adds a line in the definitionas:

Full virtualization is used to simulate a complete hardware environment, or virtual machine, in which an unmodified guest operating system (using the same instruction set as the host machine) executes in complete isolation.

The text in bold is a bit confusing. How is the same instruction set of the processor used to provide two isolated environment? Can someone explain it? ArmTrustzone manual also talk of a "virtual processor core" to provide security. Please throw some light.

thanks

Answer 1

The phrase "using the same instruction set as the host machine" means that the guest OS is not aware of the virtualization layer and behaves as if it is executed on a real machine (with the same instruction set). This is in contrast to the para-virtualization paradigm in which the guest OS is aware of virtualization and calls some specific VMM functions, i.e. hypercalls.

Answer 2

No, CPU has not additional instructions. Virtual machine instruction set is translated by a hypervisor component called VMM (virtual machine manager) to be executed on the physical CPU.

Physical CPU with assisted Virtualization introduced only a new ring 0 mode called VMX that allow the virtual machine to execute some instructions in ring 0.