What is meant by trap-and-emulate virtualization?

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I read the term trap-and-emulate virtualization in some articles on how to set up a virtual pc. Can anyone please tell me what this term means?

I understood that it definitely is some method for creating a virtual pc. But how is it done?

virtualization virtual-machine
3 Answers

Attempting a privileged instruction when in user mode causes an error to occur thus leading to trap state.

And after this the VMM (Virtual Machine Manager) gets control and analyzed the error , executes the operation as attempted by the guest and then return the control back to guest in user mode.

Note : Kernel mode privileged command runs slower due to trap and emulate

user_118811410

There are two types of operations performed by OS/Application running on Virtual Machine Manager (or Hypervisor):

  1. Non-privileged - Hypervisor directly allows OS/App to perform these operations.
  2. Privileged - Hypervisor uses the Trap-and-Emulate method to determine whether the operation is legal or illegal. It creates a trap for privileged operation first. Then, if the operation is illegal, the hypervisor terminates the operation, and if it is a legal operation, it emulates the behavior guest OS/App expects from the hardware.
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