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VMFUNC

VMFUNC allows a guest virtual machine to invoke a function provided by the virtual machine monitor (VMM) without causing a VM exit. The behavior depends on the function index specified in the EAX register.

The table after the description covers what the source and destinations can be.

DO NOT support LOCK

This instruction SHALL only be executed in VMX non-root operation. If executed in VMX root operation, it is treated as a NOP. The instruction is only supported when the "Enable VMFUNC" VM-execution control is set to 1 in the VMCS.

The function index in EAX MUST be supported by the VMM. If the function index is not supported or is invalid, the instruction triggers a general protection fault (#GP). For EPTP switching (Function 0), the VMFUNC instruction requires that the "EPTP switching" VM-execution control be enabled and a valid EPTP list be configured in the VMCS. Failure to configure the EPTP list prior to execution will result in an undefined behavior or a #GP.