VMRESUME

VMRESUME is an instruction used in hardware-assisted virtualization to resume execution of a guest virtual machine after a VMEXIT. It is part of major virtualization extensions such as Intel VT-x and AMD SVM, and serves as the return path from the hypervisor’s handling of a VMEXIT back to the running guest.

Operation and context: When a guest triggers an event that causes a VMEXIT, the processor switches to host or hypervisor mode and saves the guest state in a virtualization data structure (such as the VMCS on Intel or the VMCB on AMD). After the hypervisor completes its handling, it issues VMRESUME to re-enter the guest. The processor then restores the guest state and resumes execution at the guest instruction pointer stored in the virtualization data structure. If the VMRESUME path cannot be taken (for example, the guest state or control structure is not in a resumable state), a VM-entry failure can occur, and control may remain in the host.

Architecture-specific notes: In Intel VT-x, VMRESUME is used to re-enter a VM after a VMEXIT, following an initial VMLAUNCH. In AMD SVM, the corresponding sequence uses VMRUN to start a VM and VMRESUME to continue after exits. Across both architectures, VMRESUME is the mechanism that transfers execution back to the guest while preserving or restoring its state.

Relation to other concepts: VMRESUME is one half of the VMEXIT/VMRESUME flow. It interacts with other virtualization constructs such as VMEXIT handling, VMCS (Intel) or VMCB (AMD), and related instructions like VMCALL, VMSAVE, and VMSLOAD.

See also: VMEXIT, VMLAUNCH, VMRUN, VMCS, VMCB, VMSAVE, VMSLOAD.