Host Compute System API

https://learn.microsoft.com/en-us/virtualization/api/hcs/reference
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### Manage Virtual Machines with HCS API

Source: https://learn.microsoft.com/en-us/virtualization/api/hcs/reference/tutorial

This example shows the lifecycle of a virtual machine using HCS API, including configuration, creation, and starting the system. It uses WIL for RAII-style handle management.

```cpp
#include <windows.h>
#include <winerror.h>
#include <wil\resource.h>

// HCS API header file
#include <computecore.h>
#include <computedefs.h>
#include <computenetwork.h>
#include <computestorage.h>

#pragma comment(lib, "computecore.lib")


//
// Helper RAII objects around HCS system handle and HCS operation handle
// HCS_OPERATION handle closed by HcsCloseOperation
// HCS_SYSTEM handle closed by HcsCloseComputeSystem
//
using unique_hcs_operation = wil::unique_any<HCS_OPERATION, decltype(&HcsCloseOperation), HcsCloseOperation>;
using unique_hcs_system = wil::unique_any<HCS_SYSTEM, decltype(&HcsCloseComputeSystem), HcsCloseComputeSystem>;

//
// Create a virtual machine
//
    static constexpr wchar_t c_VmConfiguration[] = LR"(
    {
        "SchemaVersion": {
            "Major": 2,
            "Minor": 1
        },
        "Owner": "Sample",
        "ShouldTerminateOnLastHandleClosed": true,
        "VirtualMachine": {
            "Chipset": {
                "Uefi": {
                    "BootThis": {
                        "DevicePath": "Primary disk",
                        "DiskNumber": 0,
                        "DeviceType": "ScsiDrive"
                    }
                }
            },
            "ComputeTopology": {
                "Memory": {
                    "Backing": "Virtual",
                    "SizeInMB": 2048
                },
                "Processor": {
                    "Count": 2
                }
            },
            "Devices": {
                "Scsi": {
                    "Primary disk": {
                        "Attachments": {
                            "0": {
                                "Type": "VirtualDisk",
                                "Path": "c:\\HCS_Test\\utilityvm.vhdx"
                            }
                        }
                    }
                }
            }
        }
    })";

    // After setting up the JSON document, we need to call into the HCS to create
    // the compute system, in this case, an HCS VM.
    // This operation doesn't need callback
    unique_hcs_operation operation(HcsCreateOperation(nullptr, nullptr));
    unique_hcs_system system;
    THROW_IF_FAILED(HcsCreateComputeSystem(
        L"Sample", // Unique Id
        c_VmConfiguration,
        operation.get(),
        nullptr, // This parameter is not supported yet, always pass NULL
        &system));

    // We need to wait on the operation explicitly because no callback was setup
    // Result document from waiting on the operation would usually contain
    // a JSON blob with either error attribution or operation specific result data
    // (for example, compute system properties if the operation was used to call
    // ::HcsGetComputeSystemProperties).
    // Result document isn't necessarily set all the time, so make sure to check for that!
    wil::unique_hlocal_string resultDoc;
    THROW_IF_FAILED_MSG(HcsWaitForOperationResult(operation.get(), INFINITE, &resultDoc),
        "ResultDoc: %ws", resultDoc.get());
    // For a successful HcsCreateComputeSystem, result document doesn't have anything.

//
// Now that the HCS VM is created, we need to start it!
//
    THROW_IF_FAILED(HcsStartComputeSystem(
        system.get(),
        operation.get(),
        nullptr)); // This parameter is not currently supported, pass NULL.
    THROW_IF_FAILED_MSG(HcsWaitForOperationResult(operation.get(), INFINITE, &resultDoc),
        "ResultDoc: %ws", resultDoc.get());

//
// Get the VM memory property and print the result out
//
    static constexpr wchar_t c_VmQuery[] = LR"(
    {
        "PropertyTypes":[
            "Memory"
        ]
    })";
```

--------------------------------

### HcsStartComputeSystem

Source: https://learn.microsoft.com/en-us/virtualization/api/hcs/reference/hcsstartcomputesystem

Starts a compute system using the provided system and operation handles.

```APIDOC
## HcsStartComputeSystem

### Description
Starts a compute system. Callers are expected to get the operation's result using HcsWaitForOperationResult or HcsGetOperationResult.

### Syntax
`HRESULT WINAPI HcsStartComputeSystem(HCS_SYSTEM computeSystem, HCS_OPERATION operation, PCWSTR options);`

### Parameters
- **computeSystem** (HCS_SYSTEM) - Required - The handle to the compute system to start.
- **operation** (HCS_OPERATION) - Required - The handle to the operation that tracks the start operation.
- **options** (PCWSTR) - Optional - Reserved for future use. Must be NULL.

### Return Values
- **HRESULT** - Returns S_OK if the operation started successfully.
```

--------------------------------

### HcsCreateProcess

Source: https://learn.microsoft.com/en-us/virtualization/api/hcs/reference/hcscreateprocess

Starts a process in a compute system.

```APIDOC
## HcsCreateProcess

### Description
Starts a process in a compute system.

### Syntax
```cpp
HRESULT WINAPI HcsCreateProcess(
    _In_ HCS_SYSTEM computeSystem,
    _In_ PCWSTR processParameters,
    _In_ HCS_OPERATION operation,
    _In_opt_ const SECURITY_DESCRIPTOR* securityDescriptor,
    _Out_ HCS_PROCESS* process
    );
```

### Parameters
- **computeSystem** (HCS_SYSTEM) - Required - The handle to the compute system in which to start the process.
- **processParameters** (PCWSTR) - Required - JSON document of ProcessParameters specifying the command line and environment for the process.
- **operation** (HCS_OPERATION) - Required - Handle to the operation that tracks the process creation operation.
- **securityDescriptor** (const SECURITY_DESCRIPTOR*) - Optional - Reserved for future use, must be NULL.
- **process** (HCS_PROCESS*) - Required - Receives the HCS_PROCESS handle to the newly created process.

### Return Values
- **HRESULT** - Returns S_OK if the operation started successfully.
```

--------------------------------

### HcsStartComputeSystem function signature

Source: https://learn.microsoft.com/en-us/virtualization/api/hcs/reference/hcsstartcomputesystem

The C++ function signature for starting a compute system.

```C++
HRESULT WINAPI
HcsStartComputeSystem(
    _In_ HCS_SYSTEM computeSystem,
    _In_ HCS_OPERATION operation,
    _In_opt_ PCWSTR options
    );
```

--------------------------------

### HDV_PCI_DEVICE_START

Source: https://learn.microsoft.com/en-us/virtualization/api/hcs/reference/hdv/hdvpcidevicestart

Callback function signature for notifying an emulated device of VM processor startup.

```APIDOC
## HDV_PCI_DEVICE_START

### Description
Function called to notify the emulated device that the virtual processors of the VM are about to start.

### Syntax
```cpp
typedef HRESULT (CALLBACK *HDV_PCI_DEVICE_START)(
    _In_opt_ void* DeviceContext
    );
```

### Parameters
- **DeviceContext** (void*) - Required - Context pointer that was supplied to HdvCreateDeviceInstance

### Return Values
- **S_OK** - Returned if function succeeds.
- **HRESULT** - An error code is returned if the function fails.

### Requirements
- **Minimum supported client**: Windows 10, version 1607
- **Minimum supported server**: Windows Server 2016
- **Library**: ComputeCore.lib
- **Dll**: ComputeCore.dll
```

--------------------------------

### HdvCreateDeviceInstance

Source: https://learn.microsoft.com/en-us/virtualization/api/hcs/reference/hdv/hdvcreatedeviceinstance

Creates a device instance in the current host and associates it with a device emulation interface and context.

```APIDOC
## HdvCreateDeviceInstance

### Description
Creates a device instance in the current host and associates it with a device emulation interface and context.

### Syntax
```cpp
HRESULT WINAPI HdvCreateDeviceInstance(
    _In_     HDV_HOST        DeviceHost,
    _In_     HDV_DEVICE_TYPE DeviceType,
    _In_     const GUID*     DeviceClassId,
    _In_     const GUID*     DeviceInstanceId,
    _In_     const VOID*     DeviceInterface,
    _In_opt_ void*           DeviceContext,
    _Out_    HDV_DEVICE*     DeviceHandle
    );
```

### Parameters
- **DeviceHost** (HDV_HOST) - Handle to the device host in which to create the new device.
- **DeviceType** (HDV_DEVICE_TYPE) - Specifies the type of the device instance to create.
- **DeviceClassId** (const GUID*) - Supplies the client-defined class ID of the device instance to create.
- **DeviceInstanceId** (const GUID*) - Supplies the client-defined instance ID of the device instance to create.
- **DeviceInterface** (const VOID*) - Supplies a function table representing the interface exposed by the device instance.
- **DeviceContext** (void*) - Optional opaque context pointer supplied to the device instance callbacks.
- **DeviceHandle** (HDV_DEVICE*) - Receives a handle to the created device instance.

### Return Values
- **S_OK** - Returned if function succeeds.
- **HRESULT** - An error code is returned if the function fails.
```

--------------------------------

### Get Host Service Properties

Source: https://learn.microsoft.com/en-us/virtualization/api/hcs/reference/servicesample

Retrieves specific service properties like memory usage using HcsGetServiceProperties.

```C++
    static constexpr wchar_t c_ServicePropertyQuery[] = LR"(
    {
        "PropertyTypes": [
            "Memory"
        ]
    })";

    wil::unique_hlocal_string resultDoc;
    THROW_IF_FAILED(HcsGetServiceProperties(c_ServicePropertyQuery, &resultDoc));
    std::wcout << L"Service property is " << resultDoc.get() << std::endl;
```

--------------------------------

### Create and Grant VM Access to a File

Source: https://learn.microsoft.com/en-us/virtualization/api/hcs/reference/utilityfunctionsample

Creates an empty runtime state file and grants the specified compute system access to it. Requires the compute system ID to be previously initialized.

```cpp
// This assumes "Sample" has been used as the id for a compute system when created through HcsCreateComputeSystem
THROW_IF_FAILED(HcsCreateEmptyRuntimeStateFile(L"emptyfile.vmrs"));
THROW_IF_FAILED(HcsGrantVmAccess(L"Sample", L"emptyfile.vmrs"));
```

--------------------------------

### HcsSetupBaseOSLayer

Source: https://learn.microsoft.com/en-us/virtualization/api/hcs/reference/hcssetupbaseoslayer

Sets up a base OS layer for use on a host.

```APIDOC
## HRESULT HcsSetupBaseOSLayer(PCWSTR layerPath, HANDLE vhdHandle, PCWSTR options)

### Description
Sets up a base OS layer for the use on a host. The base OS layer is the first layer in the set of layers used by a container or virtual machine.

### Parameters
- **layerPath** (PCWSTR) - Required - Path to the root of the base OS layer.
- **vhdHandle** (HANDLE) - Required - The handle to a VHD.
- **options** (PCWSTR) - Required - Optional JSON document of OsLayerOptions describing options for setting up the layer.

### Return Values
- **HRESULT** - Returns an HRESULT indicating success or failure.
```

--------------------------------

### HDV_PCI_DEVICE_START Callback Syntax

Source: https://learn.microsoft.com/en-us/virtualization/api/hcs/reference/hdv/hdvpcidevicestart

Defines the function signature for the HDV_PCI_DEVICE_START callback.

```C++
typedef HRESULT (CALLBACK *HDV_PCI_DEVICE_START)(
    _In_opt_ void* DeviceContext
    );
```

--------------------------------

### HDV_PCI_DEVICE_INITIALIZE

Source: https://learn.microsoft.com/en-us/virtualization/api/hcs/reference/hdv/hdvpcideviceinitialize

Callback function signature for initializing an emulated PCI device.

```APIDOC
## HDV_PCI_DEVICE_INITIALIZE

### Description
Function invoked to initialize the emulated device. It is called as the VM is powered on.

### Syntax
```cpp
typedef HRESULT (CALLBACK *HDV_PCI_DEVICE_INITIALIZE)(
    _In_opt_ void* DeviceContext
    );
```

### Parameters
- **DeviceContext** (void*) - Context pointer that was supplied to HdvCreateDeviceInstance.

### Return Values
- **S_OK** - Returned if function succeeds.
- **HRESULT** - An error code is returned if the function fails.

### Requirements
- **Minimum supported client**: Windows 10, version 1607
- **Minimum supported server**: Windows Server 2016
- **Library**: ComputeCore.lib
- **Dll**: ComputeCore.dll
```

--------------------------------

### HdvCreateDeviceInstance C++ Syntax

Source: https://learn.microsoft.com/en-us/virtualization/api/hcs/reference/hdv/hdvcreatedeviceinstance

The function signature for creating a device instance in the host.

```cpp
HRESULT WINAPI
HdvCreateDeviceInstance(
    _In_     HDV_HOST        DeviceHost,
    _In_     HDV_DEVICE_TYPE DeviceType,
    _In_     const GUID*     DeviceClassId,
    _In_     const GUID*     DeviceInstanceId,
    _In_     const VOID*     DeviceInterface,
    _In_opt_ void*           DeviceContext,
    _Out_    HDV_DEVICE*     DeviceHandle
    );
```

--------------------------------

### HdvInitializeDeviceHostForProxy function syntax

Source: https://learn.microsoft.com/en-us/virtualization/api/hcs/reference/hdv/hdvinitializedevicehostforproxy

Defines the function signature for initializing the device host.

```C++
HRESULT WINAPI
HdvInitializeDeviceHostForProxy(
    _In_ const GUID* VmId,
    _In_ PVOID ProxyInterface_IUnknown,
    _Out_ HDV_HOST* DeviceHostHandle
    );
```

--------------------------------

### HcsSetupBaseOSVolume

Source: https://learn.microsoft.com/en-us/virtualization/api/hcs/reference/hcssetupbaseosvolume

Sets up the base OS layer for use on a host based on the mounted volume (VHD).

```APIDOC
## HcsSetupBaseOSVolume

### Description
This function sets up the base OS layer for the use on a host based on the mounted volume (VHD).

### Syntax
```cpp
HRESULT WINAPI HcsSetupBaseOSVolume(
    _In_ PCWSTR layerPath,
    _In_ PCWSTR volumePath,
    _In_ PCWSTR options
    );
```

### Parameters
- **layerPath** (PCWSTR) - Required - Path to the root of the base OS layer.
- **volumePath** (PCWSTR) - Required - The handle to a VHD.
- **options** (PCWSTR) - Required - Optional JSON document of OsLayerOptions describing options for setting up the layer.

### Return Values
- **HRESULT** - Returns an HRESULT indicating success or failure.
```

--------------------------------

### HcsImportLayer

Source: https://learn.microsoft.com/en-us/virtualization/api/hcs/reference/hcsimportlayer

Imports a container layer and sets it up for use on boot.

```APIDOC
## HcsImportLayer

### Description
Imports a container layer and sets it up for use on boot. This function is used by an application to setup a container layer that was copied in a transport format to the host.

### Syntax
```cpp
HRESULT WINAPI HcsImportLayer(
    _In_ PCWSTR layerPath,
    _In_ PCWSTR sourceFolderPath,
    _In_ PCWSTR layerData
    );
```

### Parameters
- **layerPath** (PCWSTR) - Destination path for the container layer.
- **sourceFolderPath** (PCWSTR) - Source path that contains the downloaded layer files.
- **layerData** (PCWSTR) - JSON document of layerData providing the locations of the antecedent layers that are used by the imported layer.

### Return Values
- **HRESULT** - Returns an HRESULT indicating success or failure.
```

--------------------------------

### HcsCreateEmptyGuestStateFile

Source: https://learn.microsoft.com/en-us/virtualization/api/hcs/reference/hcscreateemptygueststatefile

Creates an empty guest-state file (.vmgs) for a VM.

```APIDOC
## HcsCreateEmptyGuestStateFile

### Description
Creates an empty guest-state file (.vmgs) for a VM. This file is required for VMs that are expected to be persisted and restarted multiple times.

### Syntax
```cpp
HRESULT WINAPI HcsCreateEmptyGuestStateFile(
    _In_ PCWSTR guestStateFilePath
    );
```

### Parameters
- **guestStateFilePath** (PCWSTR) - Full path to the guest-state file to create.

### Return Values
- **HRESULT** - Returns an HRESULT indicating success or failure.

### Requirements
- **Minimum supported client**: Windows 10, version 1809
- **Minimum supported server**: Windows Server 2019
- **Header**: ComputeCore.h
- **Library**: ComputeCore.lib
- **Dll**: ComputeCore.dll
```

--------------------------------

### HcsOpenComputeSystem

Source: https://learn.microsoft.com/en-us/virtualization/api/hcs/reference/hcsopencomputesystem

Opens a handle to an existing compute system.

```APIDOC
## HcsOpenComputeSystem

### Description
Opens a handle to an existing compute system. The caller is responsible for releasing the handle using HcsCloseComputeSystem.

### Syntax
`HRESULT WINAPI HcsOpenComputeSystem(PCWSTR id, DWORD requestedAccess, HCS_SYSTEM* computeSystem);`

### Parameters
- **id** (PCWSTR) - Required - Unique Id identifying the compute system.
- **requestedAccess** (DWORD) - Required - Reserved for future use, must be GENERIC_ALL.
- **computeSystem** (HCS_SYSTEM*) - Required - Receives a handle to the compute system.

### Return Values
- **HRESULT** - Returns an HRESULT indicating success or failure.
```

--------------------------------

### HcsGetProcessInfo

Source: https://learn.microsoft.com/en-us/virtualization/api/hcs/reference/hcsgetprocessinfo

Retrieves the initial startup information of a process in a compute system.

```APIDOC
## HcsGetProcessInfo

### Description
Returns the initial startup information of a process in a compute system.

### Syntax
```cpp
HRESULT WINAPI HcsGetProcessInfo(
    _In_ HCS_PROCESS process,
    _In_ HCS_OPERATION operation
    );
```

### Parameters
- **process** (HCS_PROCESS) - Required - The handle to the process to query.
- **operation** (HCS_OPERATION) - Required - The handle to the operation that tracks the process.

### Return Values
- **HRESULT** - Returns S_OK if the operation started successfully. Callers should use HcsWaitForOperationResultAndProcessInfo or HcsGetOperationResultAndProcessInfo to retrieve the result.

### Requirements
- **Header**: ComputeCore.h
- **Library**: ComputeCore.lib
- **Dll**: ComputeCore.dll
- **Minimum supported client**: Windows 10, version 1809
- **Minimum supported server**: Windows Server 2019
```

--------------------------------

### HDV_PCI_DEVICE_INITIALIZE Callback Syntax

Source: https://learn.microsoft.com/en-us/virtualization/api/hcs/reference/hdv/hdvpcideviceinitialize

Defines the function signature for the device initialization callback.

```C++
typedef HRESULT (CALLBACK *HDV_PCI_DEVICE_INITIALIZE)(
    _In_opt_ void* DeviceContext
    );
```

--------------------------------

### HdvInitializeDeviceHostForProxy

Source: https://learn.microsoft.com/en-us/virtualization/api/hcs/reference/hdv/hdvinitializedevicehostforproxy

Initializes the device emulator host in the caller's process and associates it with the specified proxy. A successful call must be balanced by a call to HdvTeardownDeviceHost on the same thread.

```APIDOC
## HdvInitializeDeviceHostForProxy

### Description
Initializes the device emulator host in the caller's process and associates it with the specified proxy. The proxy is responsible for associating with the compute system.

### Syntax
```cpp
HRESULT WINAPI HdvInitializeDeviceHostForProxy(
    _In_ const GUID* VmId,
    _In_ PVOID ProxyInterface_IUnknown,
    _Out_ HDV_HOST* DeviceHostHandle
    );
```

### Parameters
- **VmId** (const GUID*) - The unique identifier of the compute system.
- **ProxyInterface_IUnknown** (PVOID) - The interface used to communicate with the proxy.
- **DeviceHostHandle** (HDV_HOST*) - A void pointer that receives a handle to the created device host.

### Return Value
- **S_OK** - The function succeeded.
- **HRESULT error code** - The function failed.

### Requirements
- **Minimum supported client**: Windows 10, version 1607
- **Minimum supported server**: Windows Server 2016
- **Library**: vmdevicehost.lib
- **Dll**: vmdevicehost.dll
```

--------------------------------

### HcsCreateEmptyRuntimeStateFile

Source: https://learn.microsoft.com/en-us/virtualization/api/hcs/reference/hcscreateemptyruntimestatefile

Creates an empty runtime-state file (.vmrs) for a VM.

```APIDOC
## HcsCreateEmptyRuntimeStateFile

### Description
Creates an empty runtime-state file (.vmrs) for a VM. This file is used to save a running VM and is specified in the options document of the HcsSaveComputeSystem function.

### Syntax
```cpp
HRESULT WINAPI HcsCreateEmptyRuntimeStateFile(
    _In_ PCWSTR runtimeStateFilePath
    );
```

### Parameters
- **runtimeStateFilePath** (PCWSTR) - Required - Full path to the runtime-state file to create.

### Return Values
- **HRESULT** - Returns an HRESULT indicating success or failure.

### Requirements
- **Minimum supported client**: Windows 10, version 1809
- **Minimum supported server**: Windows Server 2019
- **Header**: ComputeCore.h
- **Library**: ComputeCore.lib
- **Dll**: ComputeCore.dll
```

--------------------------------

### Open a virtual machine compute system

Source: https://learn.microsoft.com/en-us/virtualization/api/hcs/reference/computesystemsample

Opens an existing compute system by name. The system handle is managed via RAII to ensure proper cleanup.

```C++
    static constexpr wchar_t c_VmQuery[] = LR"(
    {
        "PropertyTypes":[
            "Memory"
        ]
    })";

    unique_hcs_operation operation(HcsCreateOperation(nullptr, nullptr));
    unique_hcs_system system;
    THROW_IF_FAILED(HcsOpenComputeSystem(L"Sample", GENERIC_ALL, &system));
```

--------------------------------

### HcsOpenProcess

Source: https://learn.microsoft.com/en-us/virtualization/api/hcs/reference/hcsopenprocess

Opens an existing process in a compute system.

```APIDOC
## HcsOpenProcess

### Description
Opens an existing process in a compute system.

### Syntax
```cpp
HRESULT WINAPI HcsOpenProcess(
    _In_ HCS_SYSTEM computeSystem,
    _In_ DWORD processId,
    _In_ DWORD requestedAccess,
    _Out_ HCS_PROCESS* process
    );
```

### Parameters
- **computeSystem** (HCS_SYSTEM) - The handle to the compute system in which to start the process.
- **processId** (DWORD) - Specifies the Id of the process to open.
- **requestedAccess** (DWORD) - Specifies the required access to the compute system.
- **process** (HCS_PROCESS*) - Receives the handle to the process.

### Return Values
The function returns an HRESULT.
```

--------------------------------

### Enumerate all compute systems

Source: https://learn.microsoft.com/en-us/virtualization/api/hcs/reference/computesystemsample

Lists all available compute systems and outputs the result as a JSON string.

```C++
    unique_hcs_operation enumOperation(HcsCreateOperation(nullptr, nullptr));
    THROW_IF_FAILED(HcsEnumerateComputeSystems(nullptr, enumOperation.get()));

    // print out all the compute system in JSON string
    wil::unique_hlocal_string Enumresult;
    THROW_IF_FAILED(HcsWaitForOperationResult(enumOperation.get(), INFINITE, &Enumresult));
    std::wcout << Enumresult.get() << std::endl;
```

--------------------------------

### HcsCreateComputeSystem

Source: https://learn.microsoft.com/en-us/virtualization/api/hcs/reference/hcscreatecomputesystem

Creates a new compute system using the provided configuration and operation handle.

```APIDOC
## HcsCreateComputeSystem

### Description
Creates a new compute system. The function returns an HRESULT indicating if the operation started successfully.

### Syntax
```cpp
HRESULT WINAPI HcsCreateComputeSystem(
    _In_ PCWSTR id,
    _In_ PCWSTR configuration,
    _In_ HCS_OPERATION operation,
    _In_opt_ const SECURITY_DESCRIPTOR* securityDescriptor,
    _Out_ HCS_SYSTEM* computeSystem
    );
```

### Parameters
- **id** (PCWSTR) - Required - Unique Id identifying the compute system.
- **configuration** (PCWSTR) - Required - JSON document specifying the settings of the compute system (Container, VirtualMachine, or HostedSystem).
- **operation** (HCS_OPERATION) - Required - The handle to the operation that tracks the create operation.
- **securityDescriptor** (const SECURITY_DESCRIPTOR*) - Optional - Reserved for future use, must be NULL.
- **computeSystem** (HCS_SYSTEM*) - Required - Receives a handle to the newly created compute system.

### Return Values
- **HRESULT** - Returns S_OK if the operation started successfully. Callers should use HcsWaitForOperationResult or HcsGetOperationResult to track completion.
```

--------------------------------

### HdvInitializeDeviceHost

Source: https://learn.microsoft.com/en-us/virtualization/api/hcs/reference/hdv/hdvinitializedevicehost

Initializes a device emulator host in the caller's process and associates it with the specified compute system.

```APIDOC
## HdvInitializeDeviceHost

### Description
Initializes a device emulator host in the caller's process and associates it with the specified compute system.

### Syntax
```cpp
HRESULT WINAPI HdvInitializeDeviceHost(
    _In_  HCS_SYSTEM ComputeSystem,
    _Out_ HDV_HOST*  DeviceHost
    );
```

### Parameters
- **ComputeSystem** (HCS_SYSTEM) - Required - Handle to the compute system of the VM in which the device is used. The VM's configuration must indicate that an external device host for the VM will be present.
- **DeviceHost** (HDV_HOST*) - Required - Receives the handle to the device emulator host for the VM.

### Return Value
- **S_OK** - Success
- **HRESULT** - Error code on failure
```

--------------------------------

### Enable and Use Compute System Operation Callbacks

Source: https://learn.microsoft.com/en-us/virtualization/api/hcs/reference/operationcompletionsample

Configures a compute system callback to handle operation completion events using a Windows event object for synchronization. Demonstrates that subsequent attempts to use individual operation callbacks will fail as expected.

```cpp
// Use a windows event object as the context so that we can wait on it
wil::unique_event callbackWait;
callbackWait.create();
unique_hcs_system system;
THROW_IF_FAILED(HcsCreateComputeSystem(L"Test", c_EmptyVM, HcsCreateOperation(nullptr, nullptr), nullptr, &system));
THROW_IF_FAILED(HcsSetComputeSystemCallback(
    system.get(),
    HcsEventOptionEnableOperationCallbacks,
    callbackWait.get(),
    [](HCS_EVENT* event, void* context)
    {
        WI_ASSERT(event->Type == HcsEventOperationCallback);
        wil::unique_hlocal_string resultDoc;
        THROW_IF_FAILED_MSG(HcsGetOperationResult(event->Operation, &resultDoc), "%ws", resultDoc.get());
        HcsCloseOperation(event->Operation);
        SetEvent(context);
    }));
callbackWait.wait(INFINITE);

// However, once the system callback has been set, using an operation with callback fails!
callbackWait.create();
HRESULT result = HcsStartComputeSystem(
    system.get(),
    HcsCreateOperation(nullptr, [](HCS_OPERATION operation, void* context){}),
    nullptr);
THROW_HR_IF(E_UNEXPECTED, result != HCS_E_OPERATION_SYSTEM_CALLBACK_ALREADY_SET);
```

--------------------------------

### HcsCreateEmptyGuestStateFile Syntax

Source: https://learn.microsoft.com/en-us/virtualization/api/hcs/reference/hcscreateemptygueststatefile

The function signature for creating an empty guest-state file in C++.

```C++
HRESULT WINAPI
HcsCreateEmptyGuestStateFile(
    _In_ PCWSTR guestStateFilePath
    );
```

--------------------------------

### HcsCreateEmptyRuntimeStateFile Syntax

Source: https://learn.microsoft.com/en-us/virtualization/api/hcs/reference/hcscreateemptyruntimestatefile

The function signature for creating an empty runtime-state file in C++.

```cpp
HRESULT WINAPI
HcsCreateEmptyRuntimeStateFile(
    _In_ PCWSTR runtimeStateFilePath
    );
```

--------------------------------

### HcsSetupBaseOSLayer function syntax

Source: https://learn.microsoft.com/en-us/virtualization/api/hcs/reference/hcssetupbaseoslayer

The function signature for setting up a base OS layer, requiring a path, VHD handle, and optional configuration.

```C++
HRESULT WINAPI
HcsSetupBaseOSLayer(
    _In_ PCWSTR layerPath,
    _In_ HANDLE vhdHandle,
    _In_ PCWSTR options
    );
```

--------------------------------

### HdvInitializeDeviceHost function syntax

Source: https://learn.microsoft.com/en-us/virtualization/api/hcs/reference/hdv/hdvinitializedevicehost

The function signature for initializing a device emulator host in C++.

```cpp
HRESULT WINAPI
HdvInitializeDeviceHost(
    _In_  HCS_SYSTEM ComputeSystem,
    _Out_ HDV_HOST*  DeviceHost
    );
```

--------------------------------

### HDV_PCI_DEVICE_SET_CONFIGURATION Callback Syntax

Source: https://learn.microsoft.com/en-us/virtualization/api/hcs/reference/hdv/hdvpcidevicesetconfiguration

Defines the function signature for setting the configuration of an emulated device.

```C++
typedef HRESULT (CALLBACK *HDV_PCI_DEVICE_SET_CONFIGURATION)(
    _In_opt_ void*         DeviceContext,
    _In_     UINT32        ConfigurationValueCount,
    _In_     const PCWSTR* ConfigurationValues
    );
```

--------------------------------

### HcsInitializeLegacyWritableLayer C++ Syntax

Source: https://learn.microsoft.com/en-us/virtualization/api/hcs/reference/hcsinitializelegacywritablelayer

Function signature for initializing a legacy writable layer in C++.

```C++
HRESULT WINAPI
HcsInitializeLegacyWritableLayer(
    _In_ PCWSTR writableLayerMountPath,
    _In_ PCWSTR writableLayerFolderPath,
    _In_ PCWSTR layerData,
    _In_opt_ PCWSTR options
    );
```

--------------------------------

### Utility Functions for Virtual Machines

Source: https://learn.microsoft.com/en-us/virtualization/api/hcs/reference/apioverview

Functions to configure environments for running virtual machines.

```APIDOC
## HcsCreateEmptyGuestStateFile
Create an empty guest-state file (.vmgs) for VMs.

## HcsCreateEmptyRuntimeStateFile
Create an empty runtime-state file (.vmrs) for a VM.

## HcsGrantVmAccess
Add an entry to a file's ACL that grants access for a VM.

## HcsRevokeVmAccess
Remove an entry to a file's ACL that granted access for a VM.

## HcsGrantVmGroupAccess
Grant VM group access (R/O) to the specified file.

## HcsRevokeVmGroupAccess
Remove VM group access for the specified file.

## HcsGetProcessorCompatibilityFromSavedState
Get the processor compatibility from runtime-state file (.vmrs).
```

--------------------------------

### Pause and resume a compute system

Source: https://learn.microsoft.com/en-us/virtualization/api/hcs/reference/computesystemsample

Demonstrates how to suspend a running compute system and subsequently resume it using HCS operations.

```C++
    static constexpr wchar_t c_pauseOption[] = LR"(
    {
        "SuspensionLevel": "Suspend",
        "HostedNotification": {
            "Reason": "Save"
        }
    })";

    // Assume same "system" as previous sample code
    unique_hcs_operation pauseOperation(HcsCreateOperation(nullptr, nullptr));
    THROW_IF_FAILED(HcsPauseComputeSystem(system.get(), pauseOperation.get(), c_pauseOption));

    wil::unique_hlocal_string resultDoc;
    THROW_IF_FAILED_MSG(HcsWaitForOperationResult(pauseOperation.get(), INFINITE, &resultDoc),
        "ResultDoc: %ws", resultDoc.get());

    // After some while, resume the compute system
    unique_hcs_operation resumeOperation(HcsCreateOperation(nullptr, nullptr));
    THROW_IF_FAILED(HcsResumeComputeSystem(system.get(), resumeOperation.get(), nullptr));

    THROW_IF_FAILED_MSG(HcsWaitForOperationResult(resumeOperation.get(), INFINITE, &resultDoc),
        "ResultDoc: %ws", resultDoc.get());
```

--------------------------------

### HcsSetComputeSystemCallback function syntax

Source: https://learn.microsoft.com/en-us/virtualization/api/hcs/reference/hcssetcomputesystemcallback

The function signature for registering a compute system event callback.

```C++
HRESULT WINAPI
HcsSetComputeSystemCallback(
    _In_ HCS_SYSTEM computeSystem,
    _In_ HCS_EVENT_OPTIONS callbackOptions,
    _In_opt_ const void* context,
    _In_ HCS_EVENT_CALLBACK callback
    );
```

--------------------------------

### Registering a Compute System Event Callback

Source: https://learn.microsoft.com/en-us/virtualization/api/hcs/reference/eventcallbacksample

Sets up a callback function using HcsSetComputeSystemCallback to monitor compute system events. The callback handles various HCS_EVENT types, including system exits and crash reports.

```cpp
constexpr auto c_EmptyVM = LR"(
{
    "SchemaVersion": {
        "Major": 2,
        "Minor": 1
    },
    "Owner": "Sample",
    "VirtualMachine": {
        "Chipset": {
            "Uefi": {}
        },
        "ComputeTopology": {
            "Memory": {
                "Backing": "Physical",
                "SizeInMB": 1024
            },
            "Processor": {
                "Count": 2
            }
        }
    },
    "ShouldTerminateOnLastHandleClosed": true
})";

//
// Start by creating a compute system.
//
unique_hcs_operation operation{ HcsCreateOperation(nullptr, nullptr) };
unique_hcs_system system;
THROW_IF_FAILED(HcsCreateComputeSystem(L"Test", c_EmptyVM, operation.get(), nullptr, &system));
wil::unique_hlocal_string resultDoc;
THROW_IF_FAILED_MSG(HcsWaitForOperationResult(operation.get(), INFINITE, &resultDoc), "%ws", resultDoc.get());

//
// Set the compute system's event callback function.
// This callback is used to act on events that occur on compute systems
// outside of an HCS operation. These vary on different contexts, and the
// HCS_EVENT parameter determines what happened.
//
THROW_IF_FAILED(HcsSetComputeSystemCallback(
    system.get(),
    HcsEventOptionNone,
    nullptr,
    [](HCS_EVENT* event, void*)
    {
        switch(event->Type)
        {
        case HcsEventSystemExited:
            //
            // The compute system has exited. This usually means that it has been terminated
            // via HcsTerminateComputeSystem or shutdown via HcsShutdownComputeSystem.
            // It could also be a result of an internal error in the Host Compute Service;
            // or the compute system's guest operating system turning off the system.
            //
            // Normally cleanup logic in the client side would happen here
            // because we can deterministically know when the compute system
            // is not going to be around anymore.
            //
            // EventData is a JSON document that contains the system exit status.
            //
            WI_ASSERT(event->EventData != nullptr);
            break;

        case HcsEventSystemCrashInitiated:
            //
            // The compute system's guest operating system has initiated a crash (bugcheck).
            // This event is used to notify client code about the crash to give it a chance
            // to do something before the crash completes.
            //
            // EventData is a JSON document with a guest report.
            //
            WI_ASSERT(event->EventData != nullptr);
            break;

        case HcsEventSystemCrashReport:
            //
            // The compute system's guest operating system has reported a crash (bugcheck).
            // This event is used to notify client code about the crash completed.
            //
            // EventData is a JSON document with a guest report.
            // This can be used as input to HcsSubmitWerReport.
            //
            WI_ASSERT(event->EventData != nullptr);
            break;

        case HcsEventSystemRdpEnhancedModeStateChanged:
            //
            // The compute system's RDP enhanced mode state has changed.
            //
            break;

        case HcsEventSystemSiloJobCreated:
            //
            // Reserved for future use.
            //
            break;

        case HcsEventSystemGuestConnectionClosed:
            //
            // The compute system's guest connection has been closed.
            // This notification is called regardless of the disconnection being expected or not.
            //
            break;

        case HcsEventProcessExited:
            //
            // Event notification for when an HCS_PROCESS completes.
            // The EventData of the event is a JSON document describing
            // the resulting process status.
            //
            // This event notification is only valid for when HcsSetProcessCallback
            // is used. This will never fire for a compute system's event callback
            // set via HcsSetComputeSystemCallback.
            //

            WI_ASSERT(false); // Not valid for compute systems!
            break;

        case HcsEventOperationCallback:
            // This event type is only valid if HcsEventOptionEnableOperationCallbacks

            WI_ASSERT(false); // Not valid because we've used HcsEventOptionNone!
            break;

        case HcsEventServiceDisconnect:
            //
            // Event notification to indicate when the client code
            // has lost connection to the Host Compute Service.
            // This would usually mean the service crashed or has been forcefully stopped.
            //
            break;

        case HcsEventInvalid:
        default:
            WI_ASSERT(false); // This shouldn't happen!
        }
    }));
```

--------------------------------

### HdvProxyDeviceHost function syntax

Source: https://learn.microsoft.com/en-us/virtualization/api/hcs/reference/hdv/hdvproxydevicehost

The function signature for registering a device host with a compute system.

```C++
HRESULT
WINAPI
HdvProxyDeviceHost(
    HCS_SYSTEM ComputeSystem,
    _In_ PVOID DeviceHost_IUnknown,
    DWORD TargetProcessId,
    _Out_ UINT64* IpcSectionHandle
    );
```

--------------------------------

### HcsSetComputeSystemCallback

Source: https://learn.microsoft.com/en-us/virtualization/api/hcs/reference/hcssetcomputesystemcallback

Registers a callback to receive notifications for the compute system.

```APIDOC
## HcsSetComputeSystemCallback

### Description
Registers a callback to receive notifications for the compute system.

### Syntax
```cpp
HRESULT WINAPI HcsSetComputeSystemCallback(
    _In_ HCS_SYSTEM computeSystem,
    _In_ HCS_EVENT_OPTIONS callbackOptions,
    _In_opt_ const void* context,
    _In_ HCS_EVENT_CALLBACK callback
    );
```

### Parameters
- **computeSystem** (HCS_SYSTEM) - The handle to the compute system.
- **callbackOptions** (HCS_EVENT_OPTIONS) - The option for callback, using one from HCS_EVENT_OPTIONS.
- **context** (const void*) - Optional pointer to a context that is passed to the callback.
- **callback** (HCS_EVENT_CALLBACK) - The target HCS_EVENT_CALLBACK for compute system events.

### Return Values
- **HRESULT** - Returns an HRESULT indicating success or failure.
```

--------------------------------

### HcsEnumerateComputeSystems

Source: https://learn.microsoft.com/en-us/virtualization/api/hcs/reference/hcsenumeratecomputesystems

Enumerates existing compute systems using a query and an operation handle.

```APIDOC
## HcsEnumerateComputeSystems

### Description
Enumerates existing compute systems. Callers are expected to retrieve the result using HcsWaitForOperationResult or HcsGetOperationResult.

### Syntax
`HRESULT WINAPI HcsEnumerateComputeSystems(_In_opt_ PCWSTR query, _In_ HCS_OPERATION operation);`

### Parameters
- **query** (PCWSTR) - Optional - JSON document of SystemQuery specifying a query for specific compute systems.
- **operation** (HCS_OPERATION) - Required - The handle to the operation that tracks the enumerate operation.

### Return Values
- **S_OK** - The operation started successfully.

### Operation Results
- **S_OK** - The operation finished successfully, returning a JSON document representing an array of compute system properties.
```

--------------------------------

### HdvProxyDeviceHost

Source: https://learn.microsoft.com/en-us/virtualization/api/hcs/reference/hdv/hdvproxydevicehost

Registers a device host from another process with the compute system.

```APIDOC
## HdvProxyDeviceHost

### Description
Registers a device host from another process with the compute system.

### Syntax
```cpp
HRESULT WINAPI HdvProxyDeviceHost(
    HCS_SYSTEM ComputeSystem,
    _In_ PVOID DeviceHost_IUnknown,
    DWORD TargetProcessId,
    _Out_ UINT64* IpcSectionHandle
    );
```

### Parameters
- **ComputeSystem** (HCS_SYSTEM) - Handle to the compute system to which the device host will be associated.
- **DeviceHost_IUnknown** (PVOID) - A HDV_PCI_BAR_SELECTOR specifying index of the BAR containing the address to register.
- **TargetProcessId** (DWORD) - The ID of the process containing the device host.
- **IpcSectionHandle** (UINT64*) - Receives the IPC handle to return to remote process.

### Return Value
- **S_OK** - If the function succeeds.
- **HRESULT** - An error code if the function fails.
```

--------------------------------

### HcsGetComputeSystemProperties Syntax

Source: https://learn.microsoft.com/en-us/virtualization/api/hcs/reference/hcsgetcomputesystemproperties

The function signature for querying compute system properties in C++.

```cpp
HRESULT WINAPI
HcsGetComputeSystemProperties(
    _In_  HCS_SYSTEM computeSystem,
    _In_  HCS_OPERATION operation,
    _In_opt_ PCWSTR propertyQuery
    );
```

--------------------------------

### HDV_PCI_DEVICE_GET_DETAILS

Source: https://learn.microsoft.com/en-us/virtualization/api/hcs/reference/hdv/hdvpcidevicegetdetails

Callback function signature for querying the PCI description of an emulated device.

```APIDOC
## HDV_PCI_DEVICE_GET_DETAILS

### Description
Function invoked to query the PCI description of the emulated device. This information is used when presenting the device to the guest partition.

### Syntax
```cpp
typedef HRESULT (CALLBACK *HDV_PCI_DEVICE_GET_DETAILS)(
    _In_opt_ void*           DeviceContext,
    _Out_    PHDV_PCI_PNP_ID PnpId,
    _Out_    UINT32          ProbedBars[HDV_PCI_BAR_COUNT]
    );
```

### Parameters
- **DeviceContext** (void*) - Context pointer that was supplied to HdvCreateDeviceInstance.
- **PnpId** (PHDV_PCI_PNP_ID) - Receives the vendor / device ID / ... information about the device.
- **ProbedBars** (UINT32[HDV_PCI_BAR_COUNT]) - Receives the results for probing the MMIO BARs.

### Return Values
- **S_OK** - Returned if function succeeds.
- **HRESULT** - An error code is returned if the function fails.
```

--------------------------------

### Retrieve VM Properties

Source: https://learn.microsoft.com/en-us/virtualization/api/hcs/reference/tutorial

Fetches and displays the properties of a compute system using HcsGetComputeSystemProperties.

```cpp
    THROW_IF_FAILED(HcsGetComputeSystemProperties(
        system.get(),
        operation.get(),
        c_VmQuery));
    THROW_IF_FAILED_MSG(HcsWaitForOperationResult(operation.get(), INFINITE, &resultDoc),
        "ResultDoc: %ws", resultDoc.get());

    // It's a failure if the result document doesn't have anything for
    // ::HcsGetComputeSystemProperties!
    THROW_HR_IF(E_UNEXPECTED, !resultDoc);
    wprintf(L"HCS VM properties:\n%s\n", resultDoc.get());
```

--------------------------------

### HdvTeardownDeviceHost function syntax

Source: https://learn.microsoft.com/en-us/virtualization/api/hcs/reference/hdv/hdvteardowndevicehost

The function signature for tearing down a device host in C++.

```cpp
HRESULT WINAPI
HdvTeardownDeviceHost(
    _In_ HDV_HOST DeviceHost
    );
```

--------------------------------

### HdvCreateGuestMemoryAperture

Source: https://learn.microsoft.com/en-us/virtualization/api/hcs/reference/hdv/hdvcreateguestmemoryaperture

Creates a guest RAM aperture into the address space of the calling process.

```APIDOC
## HdvCreateGuestMemoryAperture

### Description
Creates a guest RAM aperture into the address space of the calling process.

### Syntax
```cpp
HRESULT WINAPI HdvCreateGuestMemoryAperture(
    _In_  HDV_DEVICE Requestor,
    _In_  UINT64     GuestPhysicalAddress,
    _In_  UINT32     ByteCount,
    _In_  BOOL       WriteProtected,
    _Out_ void**     MappedAddress
    );
```

### Parameters
- **Requestor** (HDV_DEVICE) - Handle to the device requesting memory access.
- **GuestPhysicalAddress** (UINT64) - Base physical address at which the aperture starts.
- **ByteCount** (UINT32) - Size of the aperture in bytes.
- **WriteProtected** (BOOL) - If TRUE, the process is only granted read access to the mapped memory.
- **MappedAddress** (void**) - Receives the virtual address (in the calling process) at which the requested guest memory region has been mapped.

### Return Values
- **S_OK** - Returned if function succeeds.
- **HRESULT** - An error code is returned if the function fails.
```

--------------------------------

### HdvReadGuestMemory Syntax

Source: https://learn.microsoft.com/en-us/virtualization/api/hcs/reference/hdv/hdvreadguestmemory

The function signature for reading guest memory in C++.

```C++
HRESULT WINAPI
HdvReadGuestMemory(
    _In_                    HDV_DEVICE Requestor,
    _In_                    UINT64     GuestPhysicalAddress,
    _In_                    UINT32     ByteCount,
    _Out_writes_(ByteCount) BYTE*      Buffer
    );
```

--------------------------------

### HcsCreateProcess Function Syntax

Source: https://learn.microsoft.com/en-us/virtualization/api/hcs/reference/hcscreateprocess

The function signature for initiating a process in a compute system.

```C++
HRESULT WINAPI
HcsCreateProcess(
    _In_ HCS_SYSTEM computeSystem,
    _In_ PCWSTR processParameters,
    _In_ HCS_OPERATION operation,
    _In_opt_ const SECURITY_DESCRIPTOR* securityDescriptor,
    _Out_ HCS_PROCESS* process
    );
```

--------------------------------

### HcsInitializeWritableLayer Function Syntax

Source: https://learn.microsoft.com/en-us/virtualization/api/hcs/reference/hcsinitializewritablelayer

The function signature for initializing a writable layer in C++.

```cpp
HRESULT WINAPI
HcsInitializeWritableLayer(
    _In_ PCWSTR writableLayerPath,
    _In_ PCWSTR layerData,
    _In_opt_ PCWSTR options
    );
```

--------------------------------

### HcsRevokeVmAccess Syntax

Source: https://learn.microsoft.com/en-us/virtualization/api/hcs/reference/hcsrevokevmaccess

The function signature for HcsRevokeVmAccess as defined in ComputeCore.h.

```Cpp
HRESULT WINAPI
HcsRevokeVmAccess(
    _In_ PCWSTR vmId,
    _In_ PCWSTR filePath
    );
```

--------------------------------

### HdvCreateSectionBackedMmioRange C++ Syntax

Source: https://learn.microsoft.com/en-us/virtualization/api/hcs/reference/hdv/hdvcreatesectionbackedmmiorange

Function signature for mapping a section into device MMIO space.

```C++
HRESULT WINAPI
HdvCreateSectionBackedMmioRange(
    _In_     HDV_DEVICE             Requestor,
    _In_     HDV_PCI_BAR_SELECTOR   BarIndex,
    _In_     UINT64                 OffsetInPages,
    _In_     UINT64                 LengthInPages,
    _In_     HDV_MMIO_MAPPING_FLAGS MappingFlags,
    _In_     HANDLE                 SectionHandle,
    _In_     UINT64                 SectionOffsetInPages
    );
```

--------------------------------

### HDV_PCI_DEVICE_SET_CONFIGURATION

Source: https://learn.microsoft.com/en-us/virtualization/api/hcs/reference/hdv/hdvpcidevicesetconfiguration

Callback function invoked to set the configuration of the emulated device.

```APIDOC
## HDV_PCI_DEVICE_SET_CONFIGURATION

### Description
Function invoked to set the configuration of the emulated device.

### Syntax
```cpp
typedef HRESULT (CALLBACK *HDV_PCI_DEVICE_SET_CONFIGURATION)(
    _In_opt_ void*         DeviceContext,
    _In_     UINT32        ConfigurationValueCount,
    _In_     const PCWSTR* ConfigurationValues
    );
```

### Parameters
- **DeviceContext** (void*) - Context pointer that was supplied to HdvCreateDeviceInstance.
- **ConfigurationValueCount** (UINT32) - Number of elements in the ConfigurationValues array.
- **ConfigurationValues** (const PCWSTR*) - Array with strings representing the configurations values. These strings are provided in the VM's configuration.

### Return Values
- **S_OK** - Returned if function succeeds.
- **HRESULT** - An error code is returned if the function fails.
```

--------------------------------

### Device Virtualization API Functions

Source: https://learn.microsoft.com/en-us/virtualization/api/hcs/reference/hdv/devicevirtualization

The following C-style Windows API functions are available for managing device virtualization within the Host Compute Service.

```APIDOC
## Device Virtualization API Functions

### Description
The HCS provides a set of C-style Windows API functions for device virtualization. All functions return an HRESULT error code indicating the result of the operation.

### Available Functions
- **HdvCreateDeviceInstance**: Creates a device instance in the current host.
- **HdvCreateGuestMemoryAperture**: Creates a guest RAM aperture in the address space of the calling process.
- **HdvCreateSectionBackedMmioRange**: Maps a section into device MMIO space.
- **HdvDeliverGuestInterrupt**: Delivers a message signaled interrupt (MSI) to the guest partition.
- **HdvDestroySectionBackedMmioRange**: Unmaps a section previously mapped via HdvCreateSectionBackedMmioRange.
- **HdvInitializeDeviceHost**: Initializes a device emulator host in the caller's process.
- **HdvInitializeDeviceHostForProxy**: Initializes the device emulator host and associates it with a proxy.
- **HdvPciDeviceGetDetails**: Queries the PCI description of the emulated device.
- **HdvPciDeviceInitialize**: Initializes the emulated device.
- **HdvPciDeviceSetConfiguration**: Sets the configuration of the emulated device.
- **HdvPciDeviceStart**: Notifies the emulated device that virtual processors are starting.
- **HdvPciDeviceStop**: Notifies the emulated device that virtual processors are stopping.
- **HdvPciDeviceTeardown**: Tears down the emulated device.
- **HdvPciReadConfigSpace**: Executes a read into the emulated device's PCI config space.
- **HdvPciReadInterceptedMemory**: Executes an intercepted MMIO read for the emulated device.
- **HdvPciWriteConfigSpace**: Executes a write into the emulated device's PCI config space.
- **HdvPciWriteInterceptedMemory**: Executes an intercepted MMIO write for the emulated device.
- **HdvProxyDeviceHost**: Registers a device host from another process with the compute system.
- **HdvReadGuestMemory**: Reads guest primary memory (RAM) contents into a buffer.
- **HdvRegisterDoorbell**: Registers a guest address to trigger an event on writes.
- **HdvTeardownDeviceHost**: Tears down the device emulator host in the caller's process.
- **HdvUnregisterDoorbell**: Unregisters a doorbell notification.
- **HdvWriteGuestMemory**: Writes the contents of a specified buffer to guest primary memory (RAM).
```
Tokens:
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