VMBus Configuration Registry Location in Windows

This article explains where the Windows Registry records active configuration data for system-wide virtual machine bus (VMBus) interfaces. It outlines the specific registry paths used by the operating system, describes the roles of the hardware enumeration and service keys, and clarifies how Hyper-V and guest virtual machines track active VMBus devices.

Primary VMBus Registry Paths

In Windows, the active configuration for system-wide virtual machine bus (VMBus) interfaces is stored under the HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet hive. The Windows kernel and the VMBus root/child drivers use two primary locations to manage these interfaces:

1. Hardware Enumeration Key

The active hardware instances and allocated resources for VMBus devices are registered under:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\VMBUS

Inside this key, each synthetic device communicating across the VM bus (such as synthetic network adapters, SCSI controllers, and video devices) is assigned a unique subkey based on its device class GUID and instance ID.

Key sub-entries under each device node include: * Device Parameters: Contains operational parameters specific to that virtual interface instance. * Control: Maintains active state information populated dynamically by the Plug and Play (PnP) manager during system boot.

2. VMBus Driver Service Key

The core driver configuration and startup settings for the virtual machine bus itself are located under:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\vmbus

This key defines how the vmbus.sys driver initializes, manages communication channels between the host hypervisor and the guest partition, and allocates memory partitions.

Key values within this path include: * Start: The startup type for the VMBus driver (typically set to 0 for boot-start). * Parameters: Global channel parameters, buffer sizes, and interrupt handling settings for the active bus session.

Hyper-V Host-Level Interface Tracking

On Hyper-V host systems managing multiple guest partitions, the system-wide integration services and virtual endpoint configurations are also tracked under:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\VmGuestInterface

This key manages runtime configuration exchanges between the host virtualization infrastructure and guest VMBus endpoints.

Inspecting VMBus Settings via Regedit

  1. Open the Run dialog by pressing Win + R, type regedit, and press Enter.
  2. Navigate to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\VMBUS to view all currently enumerated synthetic devices.
  3. Expand individual device GUID folders to inspect assigned drivers, hardware IDs, and active resource allocations.