Hyper-V settings and configuration (Windows Server 2025)

Hyper-V Configuration Parameters

Сonfiguration surfaces exposed by Hyper-V on Windows Server 2025 with March 2026 patch.

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Contents

1. Registry — User-Mode Services

   §	Key	Binaries
   1.1	HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Virtualization	vmms.exe vmwp.exe
   1.2	HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Virtualization\Worker	vmms.exe vmwp.exe
   1.3	HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Virtualization\VML	vmms.exe vmcompute.exe computecore.dll
   1.4	HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Virtualization\Migration	vmms.exe vmwp.exe
   1.5	HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Virtualization\Replication	vmms.exe
   1.6	HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Virtualization\VirtualDeviceDirectory\<CLSID>	vmms.exe
   1.7	HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Virtualization\Worker\Fc\<port>	vmms.exe
   1.8	HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Virtualization\Containers	vmcompute.exe vmusrv.dll
   1.9	HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Virtualization\FlexIOV …\TimeSync …\VmSession …\FibreChannel …\WorkerAppContainer	vmflexio.dll icsvc.dll vmsynthfcvdev.dll vmwpctrl.dll
   1.10	HKLM\SOFTWARE\Microsoft\HgsClient	hgclientservice.dll
   1.11	Various SYSTEM\CurrentControlSet keys	icsvc.dll vmictimeprovider.dll vmicrdv.dll icsvcvss.dll
   1.12	HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Virtualization (vsconfig.dll facade)	vmms.exe vmwp.exe
   1.13	Various OS keys	vmms.exe vmcompute.exe

2. Registry — Kernel-Mode Drivers

   §	Key	Driver(s)
   2.1	HKLM\SYSTEM\CurrentControlSet\Services\vid\Parameters	vid.sys
   2.2	HKLM\SYSTEM\CurrentControlSet\Services\winhvr\Parameters …\hvservice …\hvcrash\Parameters	winhv.sys winhvr.sys hvservice.sys hvcrash.sys
   2.3	HKLM\SYSTEM\CurrentControlSet\Services\vmbus\Parameters …\vmbkmclr\Parameters …\hvsocket	vmbus.sys vmbusr.sys vmbkmcl.sys vmbkmclr.sys hvsocket.sys
   2.4	HKLM\SYSTEM\CurrentControlSet\Services\storvsp …\storvsc\Parameters\Device …\vhdmp\Parameters	storvsp.sys storvsc.sys vhdmp.sys vhdparser.sys pvhdparser.sys vmstorfl.sys
   2.5	HKLM\SYSTEM\CurrentControlSet\Services\VmsMp\Parameters	vmswitch.sys
   2.6	Per-device SW key (via WDF/PnP)	pcip.sys
   2.7	HKLM\SYSTEM\CurrentControlSet\Services\Video\Virtualization	HyperVideo.sys
   2.8	HKLM\SYSTEM\CurrentControlSet\Services\hyperkbd\Parameters	hyperkbd.sys
   2.9	HKLM\SYSTEM\CurrentControlSet\Services\wcifs\Parameters	wcifs.sys
   2.10	— (no driver-specific registry config)	dmvsc.sys vmgencounter.sys vpcivsp.sys VMBusHID.sys …
   2.11	HKLM\SYSTEM\CurrentControlSet\Control\Hypervisor + BCD {hypervisorsettings}	hvloader.dll winhvr.sys

3. Group Policy / MDM Policies

4. WMI Schema (root\virtualization\v2)

5. Client-Side Settings (UI preferences)

6. Environment Variables

7. Configuration Files (INI / JSON / Other)

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Sections below are populated by parallel extraction from decompiled binaries. See individual sections for per-component details and binary!function source references.

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1. Registry — User-Mode Services

Sources: vmms.exe (VM management service), vmwp.exe (per-VM worker), vmcompute.exe (Host Compute Service), computecore.dll, vmmsprox.dll.

Primary base key for almost everything: HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Virtualization

1.1. Global host settings — HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Virtualization

ValueName	Type	Binary	Purpose
AllowGen1VmScaleUp	REG_DWORD	vmms.exe	Allow scale-up of Gen1 VMs
AllowGen2VmScaleUp	REG_DWORD	vmms.exe	Allow scale-up of Gen2 VMs
AccessCheckFlags	REG_DWORD	vmms.exe!AuthorizationUtilities::Details::GetAccessCheckFlags	Authorization-manager access-check flag override (default 0)
DisableNonBufferedCopyWithFileFlush	REG_DWORD	vmms.exe	VHD copy IO policy
EnableGPUOvercommit	REG_DWORD	vmms.exe	Enable GPU overcommit
EnableSecureBootTemplateCache	REG_DWORD	vmms.exe	Cache Secure Boot templates
FhrTaskDrainTimeoutMs	REG_DWORD	vmms.exe!VmmsVmPhuManager shutdown	FHR task drain timeout on service stop (default 60 000 ms)
IfuErrataMitigations	REG_DWORD	vmms.exe!VmProcessorSettings::GetDefaultIfuErrataMitigations	In-field-update errata mitigation enable flag (default 0)
ManagementVtlDumpSizeOverrideMb	REG_DWORD	vmms.exe!CreateConfigurationForWorkerProcess	Management-VTL crash-dump size override in MB (default 512)
BiosEnableNetworkMediaState	REG_DWORD	vmms.exe!CreateConfigurationForWorkerProcess	Enable BIOS reporting of NIC media-connect state (default 0)
RequireSecureDeviceAssignment	REG_DWORD	vmms.exe	Require secure DDA
RequireSupportedDeviceAssignment	REG_DWORD	vmms.exe	Require supported DDA device
SkipMetrics	REG_DWORD	vmms.exe	Skip metrics collection
StartupWaitTimeout	REG_DWORD	vmms.exe!VmmsVirtualMachine::CreateInitContext	Seconds to wait for worker-process startup (default 300; 600 for shielded path)
VmPhuFeatures	REG_DWORD	vmms.exe!VmmsVmPhuManager::UpdatePhuSettingsFromRegistry	Per-host-update handle-brokering feature bitmask (default 0x1007 = 4103)
VssThreadPoolSize	REG_DWORD	vmms.exe	VSS thread-pool size
TraceVmmsWorkerManagerWPTracking	REG_DWORD	vmms.exe	WorkerManager WP-tracking trace flag
CheckpointValidatePerfmonPebs	REG_DWORD	vmms.exe	Perfmon PEBS validation at checkpoint
EnableMpx	REG_DWORD	vmms.exe	Enable Intel MPX
ForceSmtEnablement	REG_DWORD	vmms.exe	Force SMT even when policy disallows
TraceGuestStateFileDebugLogs	REG_DWORD	vmms.exe	Trace guest-state file debug logs
ShutdownTimeout	REG_DWORD	vmms.exe	SCM shutdown worker timeout
CurrentVmVersion	REG_SZ	vmms.exe	Current VM schema version
CompatibleVmVersion	REG_SZ	vmms.exe	Compatible VM schema version
CurrentVdevVersion	REG_SZ	vmms.exe	Current vdev version
CompatibleVdevVersion	REG_SZ	vmms.exe	Compatible vdev version
EnableExdiDebugger	REG_DWORD	vmwp.exe	Enable EXDI kernel debugger
GuestControlTimeoutInMilliseconds	REG_DWORD	vmwp.exe!VirtualMachine::GuestControlStart	Timeout waiting for guest-control start handshake (default 5000)
Firmware Version	REG_SZ	vmwp.exe	Firmware version string
UefiCrashDumpPath	REG_SZ	vmwp.exe	UEFI crash dump path
CpuIdHideHyperVLeaves	REG_DWORD	vmwp.exe	Hide Hyper-V CPUID leaves
StartVtl0TimeoutInSeconds	REG_DWORD	vmwp.exe	VTL0 start timeout
EnableAllZeroBufferWrite	REG_DWORD	vmwp.exe (restore-init, msvml_gmo_restore)	Allow writing all-zero buffers during saved-state restore (default 0)
HvsAsyncWarningTimeoutMs	REG_DWORD	vmwp.exe!HvsPerf init lambda	HVSocket async-op warning threshold in ms (default 10 000)
DisableResiliency	REG_DWORD	vmwp.exe	Disable worker resiliency
AllowSpillingForHvDeposits	REG_DWORD	vmwp.exe	Allow HV deposit spilling
UseSystemPartitionForHvDeposits	REG_DWORD	vmwp.exe	Use system partition for HV deposits
UseSystemPartitionForPhysicalBuffers	REG_DWORD	vmwp.exe	Use system partition for physical buffers
AutoHugePagesEnabled	REG_DWORD	vmwp.exe	Enable auto huge pages
InitialBufferSizeInBits	REG_DWORD	vmwp.exe!GpaAccessTrackerUtilities::ReadRegistryConfigValue	GPA access-tracker initial bitmap size in bits
InvocationKind	REG_DWORD	vmwp.exe!VmMigrationVDevOperationSettings::ExecutionPolicies	When to invoke VDev migration method (pre/post/around; default 0)
ErrorAction	REG_DWORD	vmwp.exe!VmMigrationVDevOperationSettings::ExecutionPolicies	How to treat errors from VDev migration method (ignore/fail; default 0)
InputListFilter	REG_DWORD	vmwp.exe!VmMigrationVDevOperationSettings::ExecutionPolicies	Filter applied to input VDev list before method invocation (default 0)
ListsTransform	REG_DWORD	vmwp.exe!VmMigrationVDevOperationSettings::ExecutionPolicies	Transform rule applied across input/output VDev lists (default 0)
OperationFlags	REG_DWORD	vmwp.exe!VmMigrationVDevOperationSettings::ExecutionPolicies	Bitmask controlling per-method VDev migration op behavior (default 0)
EnableVirtualSlitRawValues	REG_DWORD	vmwp.exe	Enable virtual SLIT raw values
MinVmVersionForCpuBasedMitigations	REG_SZ	vmwp.exe	Min VM version for CPU mitigations
ForceRsbaOn	REG_DWORD	vmwp.exe	Force RSBA on
NoAutomaticSmtEnablement	REG_DWORD	vmwp.exe	Disable auto-SMT enablement
EmulationEnabled	REG_DWORD	vmwp.exe	CPU emulation enabled
WaitForDebuggerOnEmulationFailure	REG_DWORD	vmwp.exe	Wait for debugger on emulation fail
Enabled	REG_DWORD	vmwp.exe!MemoryManager::CreateRam (under GpaAccessTracker subkey — NOT a top-level flag)	Enables GPA access-tracker logging during RAM create
Interfaces	REG_MULTI_SZ	vmwp.exe!ReadSingleVDevClassInfo	List of interface GUIDs supported by a virtual-device class (per-VDev subkey)
ServerExecutable	REG_SZ	vmcompute.exe	HCS server executable

Per-VM subkey: HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Virtualization\<VM-GUID> — stores Description, ElementName (REG_SZ).

1.2. Worker tuning — HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Virtualization\Worker

ValueName	Type	Purpose
PendingOperationWaitSeconds	REG_DWORD	Wait time for pending worker ops
ValidatePerfmon	REG_DWORD	Validate perfmon on worker
ValidatePerfmonPebs	REG_DWORD	Validate perfmon PEBS
ValidatePerfmonIpt	REG_DWORD	Validate perfmon IPT
AllowEarlyRealize	REG_DWORD	Allow early VHD realize
IncludeFixingRealizedVhdAcls	REG_DWORD	Fix VHD ACLs on realize
EventLogProgressIntervalSec	REG_DWORD	Event-log progress interval
CopyFileApiConfig	REG_DWORD	CopyFile API variant for storage-migration (vmms.exe!StorageMigrationBase::CopyFileW)
FileSystemsToSkipParentPathTransformation	REG_MULTI_SZ	FS names skipped in parent-path rewrite (vmms.exe!StorageMigrationBase::GetParentPath)
FcWMIQueryRetryCount	REG_DWORD	FC WMI query retry count
HbaLunTimeout	REG_DWORD	HBA LUN timeout
HideHypervisorPresent	REG_DWORD	Hide hypervisor CPUID leaves (vmwp.exe)
MaxNestedTlbSize	REG_DWORD	Max nested TLB size 0..10; values >10 silently rejected (vmwp.exe; default 0 = off)
RamOpConcurrencyMin	REG_DWORD	Min RAM-op worker threads (vmwp.exe!GmoRamOperation::Initialize; default 4; must be ≤ RamOpConcurrencyMax)
RamOpConcurrencyMax	REG_DWORD	Max RAM-op worker threads (vmwp.exe!GmoRamOperation::Initialize; default 16; must be ≥ RamOpConcurrencyMin)
RamOpConcurrencyMemScale	REG_DWORD	Memory-per-thread scale for RAM-op concurrency (vmwp.exe!GmoRamOperation::Initialize; default 0)
RamOpCompressDisableMergePageRuns	REG_DWORD	Disable merging of compressed zero-page runs (vmwp.exe!GmoRamOperation::Initialize; default 0)
DisableTemplateFilePrefetch	REG_DWORD	Skip template-VM file prefetch (vmwp.exe!WorkerConfiguration::InitializeRuntimeStateFromTemplate; default 0)
SaveVmOnTripleFaultFile	REG_SZ	Path for saved-state file on guest triple-fault (vmwp.exe!GuestErrorSaveStateFile)
SaveVmOnBugcheck	REG_DWORD	Save VM state on guest bugcheck instead of reset (vmwp.exe!WorkerConfiguration::SaveVmOnGuestBugcheck; default 0)

1.3. VML (Virtualization Management Library) — HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Virtualization\VML

Shared by vmms.exe, vmcompute.exe, computecore.dll.

ValueName	Type	Purpose
LeakWaitSeconds	REG_DWORD	Leak-detection wait
TraceFlags	REG_DWORD	Tracing flags
StopLevel	REG_DWORD	Debug stop level
DebugBreakEnabled	REG_DWORD	Enable debug break
TraceLevel	REG_DWORD	Global trace level
ClientAssertMask	REG_DWORD	Assert-handling bitmask

HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Virtualization\VML\TraceLevelsEnabled — per-channel trace levels; value names are Trace0, Trace1, … (N = channel index), each REG_QWORD.

1.4. Live Migration — HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Virtualization\Migration

ValueName	Type	Purpose
EnableVirtualSystemMigration	REG_DWORD	Master enable for LM
EnableLoopbackMigration	REG_DWORD	Allow loopback migration
EnableVirtualSystemToSuspendedMigration	REG_DWORD	Migration to suspended state
AuthenticationType	REG_DWORD	Migration auth type — 0 = CredSSP, 1 = Kerberos (matches Msvm_VirtualSystemMigrationServiceSettingData.AuthenticationType ValueMap and the Set-VMHost -VirtualMachineMigrationAuthenticationType {CredSSP|Kerberos} cmdlet)
UseStorageCachedCredentials	REG_DWORD	Use cached creds for storage migration
MaximumActiveVmMigrationCount	REG_DWORD	Max active VM migrations (default 2; no upper cap enforced)
MaximumActiveStorageMigrationCount	REG_DWORD	Max active storage migrations (default 2; no upper cap enforced)
MaximumActiveTransfers	REG_DWORD	Max active transfers (default 6; valid 6..1006 — out-of-range resets to 6)
EnableCompression	REG_DWORD	Enable compression
EnableSmbMemoryCompression	REG_DWORD	SMB memory compression
EnableSmbStorageCompression	REG_DWORD	SMB storage compression
EnableSmbTransport	REG_DWORD	SMB transport enable
EnableAccessTracking	REG_DWORD	Enable access tracking
ClusterCommonNodeVmSet	REG_SZ	Cluster common node VM set
CompressorCpuRequirement	REG_DWORD	Compressor CPU requirement
DecompressorCpuRequirement	REG_DWORD	Decompressor CPU requirement
ExtraCompressorBufferCount	REG_DWORD	Extra buffers beyond per-worker baseline (default 1; vmwp.exe!GetCompressorBufferCount)
CompressorBufferSize	REG_DWORD	Compressor buffer size
VplessNodeCompressorVpCount	REG_DWORD	Compressor VP count on VP-less node: 0 = off (default), 1..64; values >64 capped to 64 (vmwp.exe!GetCompressorWorkerCount)
CompressorLpUtilizationHighThreshold	REG_DWORD	LP CPU % above which compressor throttles down (default 85; max 100 — values >100 capped; vmms.exe!GetCompressorLpMonitorThresholds)
CompressorLpUtilizationLowThreshold	REG_DWORD	LP CPU % below which compressor scales up (default 70; capped at HighThreshold if LowThreshold > HighThreshold)
LmMemoryChunkPageCount	REG_DWORD	LM memory-transfer chunk size in pages (default 0x4000 = 16384; min 1; max 0x100000 = 1M pages; vmwp.exe!VmMigrationSettings::GetLmMemoryChunkPageCount)
LowNetworkUtilizationHigherThresholds	REG_DWORD	Upper % bound for "low-network" detection (default 40)
LowNetworkUtilizationLowerThresholds	REG_DWORD	Lower % bound for "low-network" detection (default 20)
MemoryWalkerCount	REG_DWORD	Threads scanning guest memory during migration (default 4; min 1; max 128 — values >128 capped to 128; 0 = use default)
NetworkBufferCount	REG_DWORD	Network buffer count (default 32; min 1; max 1024 — values >1024 capped; 0 = use default)
TcpTransportCompletionThreads	REG_DWORD	TCP-transport IO-completion threads (default 4; min 1; max 64 — values >64 capped; 0 = use default)
SmbTransportMaximumPagesPerSendIo	REG_DWORD	Max pages per SMB send I/O (default 256; 64 for compressed transfers)
TcpBufferSize	REG_DWORD	TCP send/recv buffer size
TcpSocketAsyncReceiveBufferSize	REG_DWORD	Async receive buffer size
MemoryTransferSMBShareMaxUses	REG_DWORD	Max concurrent connections on LM memory-transfer SMB share (vmms.exe!VmmsVmMigrationVidShare::SmbShareCreate)
StorageMigrationSMBShareMaxUses	REG_DWORD	Max concurrent connections on storage-migration SMB share (default 3; vmms.exe!VmmsVsmFileShare::SmbShareCreate)

HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Virtualization\Migration\Networks\<n> — per-network live-migration entry (one subkey per configured network, <n> = index):

ValueName	Type
SubnetNumber	REG_SZ
PrefixLength	REG_DWORD
Metric	REG_DWORD
Tags	REG_MULTI_SZ

1.5. Hyper-V Replica — HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Virtualization\Replication

ValueName	Type	Purpose
ApplyChangeReplicaDiskThrottle	REG_DWORD	Max pending apply-log queue length per replica disk (default 4; vmms.exe!FrCtLogApplyThrottler::GetMaxQueueLength)
ApplyVHDLimit	REG_DWORD	Max concurrently-applying VHDs per replica VM (vmms.exe!FrCtLogApplyThrottler::GetVHDsPerVM)
ApplyVMLimit	REG_DWORD	Max concurrently-applying VMs per primary host (vmms.exe!FrCtLogApplyThrottler::GetVMsPerPrimary)
EnableFirstApplyLogFileCheck	REG_DWORD	Verify parent-ID on first apply log file (default 0; vmms.exe!FrCtLogApplier::IsFirstLogFileParentIdCheckEnabled)
ReplicaStorageLocation	REG_SZ	Default replica storage path
TrustGroup	REG_SZ	Replica trust group
DisplayName	REG_SZ	Replication broker display name
AllowedAuthenticationType	REG_DWORD	Allowed replication auth — 1 = Kerberos, 2 = Certificate, 3 = Both (from Msvm_ReplicationServiceSettingData ValueMap)
MonitoringInterval	REG_DWORD	Monitoring interval
MonitoringStartTime	REG_DWORD	Monitoring start time
IsBrokerOptional	REG_DWORD	Cluster broker role is optional for replication (default 0; vmms.exe!FailoverReplicationSettings::IsBrokerOptional)
DisableCertRevocationCheck	REG_DWORD	Disable cert revocation check
RecoveryServerEnabled	REG_DWORD	Recovery server enabled
AllowUntrustedRootCAOnReplica	REG_DWORD	Allow untrusted root CA on replica
CTBlockStageClientTimeoutMs	REG_DWORD	Client-side timeout for CT block-stage RPC (default 600 ms; vmms.exe!FrCtApi::GetBlockStageClientTimeout)

HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Virtualization\Replication\CTDiagnostics

ValueName	Type
GroupSwitchTraceFlag	REG_SZ
CTTraceFlags	REG_DWORD

HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Virtualization\Replication\ReferencePoint

ValueName	Type
CDPReferencePointAgeingTimeoutInHours	REG_QWORD
StageTimeOutsDefined	REG_SZ

1.6. Virtual Device Directory — HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Virtualization\VirtualDeviceDirectory\<CLSID>

Defines every virtual device (synthetic NIC, SCSI controller, vGPU, etc.).

ValueName	Type	Purpose
Name	REG_SZ	Device display name
AdditionalClassNames	REG_MULTI_SZ	Additional class names
RootDeviceType	REG_SZ	Root device type
SupportedResourceTypes	REG_MULTI_SZ	Supported CIM resource types
SupportedResourceType	REG_SZ	Supported resource type (single)
WmiFactoryCLSID	REG_SZ	WMI factory CLSID
WmiComponentCLSID	REG_SZ	WMI component CLSID
Type	REG_DWORD	Device type
SupportedSubTypes	REG_MULTI_SZ	Supported subtypes
HotAddSupportedSubTypes	REG_MULTI_SZ	Hot-add supported subtypes
HotRemoveSupportedSubTypes	REG_MULTI_SZ	Hot-remove supported subtypes
VMVersionIntroduced	REG_SZ	Min VM version for device
IsPresentByDefault	REG_DWORD	Present by default
MaxParentPools	REG_DWORD	Max parent pools

HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Virtualization\ComponentDirectory: Context (REG_BINARY), Flags (REG_DWORD), ServicingVersion (REG_SZ).

1.7. Virtual Fibre Channel — HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Virtualization\Worker\Fc\<port>

ValueName	Type	Purpose
PortFriendlyName	REG_SZ	Virtual FC port friendly name
HbaInstanceName	REG_SZ	HBA instance name
NodeWWN	REG_BINARY	FC NodeWWN
PortWWN	REG_BINARY	FC PortWWN
SanTag	REG_SZ	SAN tag
SwitchFriendlyName	REG_SZ	FC switch friendly name
SwitchName	REG_SZ	FC switch name
StaticPortFriendlyName	REG_SZ	Static port friendly name
StaticPortName	REG_SZ	Static port name

Fabric subkey: CurrentWWNNAddress, MinimumWWPNAddress, MaximumWWPNAddress, CurrentWWPNAddress (all REG_BINARY).

1.8. Containers / Utility VM — HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Virtualization\Containers

Sources: vmcompute.exe (UVM lifecycle), vmusrv.dll (VSMB server).

ValueName	Type	Binary	Purpose
TemplateVmCount	REG_DWORD	vmcompute.exe	Pre-warmed template VM count
DirectMapRangeSizeMB	REG_DWORD	vmcompute.exe	Direct-map range size (MB)
ProcessorCount	REG_DWORD	vmcompute.exe	UVM processor count
SharedMemorySizeMB	REG_DWORD	vmcompute.exe	UVM shared-memory size (MB)
VSmbWorkerCpus	REG_DWORD	vmusrv.dll (Smb2 init)	VSMB server worker-thread count
VSmbDisableOplocks	REG_DWORD	vmusrv.dll	Disable oplocks for VSMB server
VSmbDisablePseudoOplocks	REG_DWORD	vmusrv.dll	Disable pseudo-oplocks
VSmbForceLevelIIOplocks	REG_DWORD	vmusrv.dll	Force level-II oplocks only
VSmbMaxCredits	REG_DWORD	vmusrv.dll	SMB2 credit ceiling per VSMB session
VSmbEnableTestShares	REG_DWORD	vmusrv.dll	Expose VSMB test shares (diag)

Subkeys: UtilityVm, UtilityVm\Memory Management, Diagnostics, Debug, Credentials\<cred name> (REG_BINARY saved credentials).

1.9. Per-feature subtrees under HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Virtualization

Keys populated by worker DLLs, separate from the Worker/VML/Migration trees.

HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Virtualization\FlexIOV — read by vmflexio.dll!Settings::Query*:

ValueName	Type	Default	Purpose
Vtl2CommunicationErrorAction	REG_DWORD	1 (valid 1-2)	Action on VTL2 comms error (1 = log, 2 = bugcheck-class)
Vtl2DeviceBindingTimeoutSeconds	REG_DWORD	60	VTL2 device-binding timeout
(disabled-device list)	REG_MULTI_SZ	-	WHEA PFA disabled-device GUID list (Settings::QueryWheaPfaDeviceDisabled)

HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Virtualization\TimeSync — read by icsvc.dll (IC TimeSync core):

ValueName	Type	Default	Purpose
TimeSampleWindowInMicroseconds	REG_DWORD	-	Time-sample window in µs (preferred)
TimeSampleWindow	REG_DWORD	-	Legacy µs form (fallback)

HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Virtualization\VmSession — read by icsvc.dll (PowerShell Direct listener):

ValueName	Type	Default	Purpose
RequirePsDirectAuthentication	REG_DWORD	-	Require authentication for PowerShell Direct sessions

HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Virtualization\PerformanceTracing — opened by vmdynmem.dll to gate extra perf tracing (subkey existence = enable).

HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Virtualization\FibreChannel — read by vmsynthfcvdev.dll, REG_MULTI_SZ list of GUIDs for FC devices disabled for synthetic passthrough.

HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Virtualization\MinimumMacAddress / MaximumMacAddress (REG_BINARY, 6 bytes) — host MAC pool range, read by VmSynthNic.dll and NetMgmtIF.dll. HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Virtualization\Worker\CurrentMacAddress (REG_BINARY) — last allocated MAC cursor, read and written by MAC allocator.

HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Virtualization\WorkerAppContainer (REG_DWORD) — read by vmwpctrl.dll!VmWpCtrl::LoadWorkerAppContainerPolicy; gates AppContainer isolation for vmwp.exe worker process.

1.10. Host Guardian Service client — HKLM\SOFTWARE\Microsoft\HgsClient

Read by hgclientservice.dll!HgRegistryConfiguration (bound via hgsclientplugin.dll). Separate from the HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Virtualization tree.

ValueName	Type	Default	Purpose
Mode	REG_SZ	-	HGS client mode (RegistryUtilities::QueryRegistryKeyForString)
LocalCACertSupported	REG_DWORD	0	Enable local CA-cert path (non-HGS attestation)
MaxRetries	REG_DWORD	-	HTTP retry count for HGS calls
RequestTimeout	REG_DWORD	-	Single-HTTP-request timeout (ms)
OperationTimeout	REG_DWORD	-	Total-operation timeout (ms)
FallbackService	REG_MULTI_SZ	-	Fallback HGS service URL list

The MSFT_HgsClientConfiguration WMI class (sec 4.5) is a view over this key.

1.11. Integration-service / RDP / time provider keys

• HKLM\SYSTEM\CurrentControlSet\Services\W32Time\TimeProviders\VMICTimeProvider\Parameters\IPC\UniqueId (REG_SZ) — persisted by icsvc.dll!ICTimeSyncIpc::PersistUniqueId, read by vmictimeprovider.dll!ICTimeSyncIpc::Get* to match W32Time provider identity.
• HKLM\SYSTEM\CurrentControlSet\Services\VmHostAgent\Parameters\VMEndpoints\<VM-GUID> (REG_BINARY blobs) — per-VM RDP endpoint persistence, read/written by vmicrdv.dll.
• HKLM\SOFTWARE\Microsoft\Virtualization\ExcludedVssWriters\ExcludedWriters (REG_MULTI_SZ) — read by icsvcvss.dll; VSS writer GUIDs skipped during host-initiated backup.
• HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Reliability\Shutdown — written by icsvcvss.dll!VssClientBase::ChangeRegistryValuesForPlannedShutdown: Comment, ReasonCode, Timestamp (planned-shutdown tagging, copies HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Reliability\LastAliveStamp).

1.12. Host-wide settings facade — vsconfig.dll!VirtualizationSettings

Central ISettingsStore facade used by vmms.exe / worker processes / wizards. Backing store resolves to keys under HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Virtualization; the properties below are named lookups exposed by the facade (each has a dedicated Get*/Set* method; the literal value-name is the property name unless overridden by the store):

Property	Purpose
AllowFirmwareLoadFromFile	Allow UEFI firmware to be loaded from arbitrary file
AllowedHashAlgorithms	Permitted TPM/attestation hash algorithms
AzureFeatureSetEnabled	Master gate for Azure-specific feature branches
BalancerIncludeMinroot	Include Minroot in CPU balancer scope
ConfigurationStorePath	Defaults to %ProgramData%\Microsoft\Windows\Hyper-V
CompatibleVmVersion / CurrentVmVersion / DefaultVmVersion / ServicingVmVersion	VM config-version policy (all four readable individually)
DefaultVirtualHardDiskCachingMode	Default VHD cache mode for newly created VHDs
DisableSelfSignedCertificateGeneration	Block self-signed cert fallback
EnableFirmwareDebugging	Enable UEFI debug output
EnhancedMode	Default Enhanced Session Mode state for new VMs
HyperVLowMemoryThresholdInPages	Host low-memory threshold
ManagementVtlUpgradePolicy	Management-VTL upgrade policy
MaximumPressureLevelVmStartup	Memory-pressure level above which VM start is refused
MemoryAllocationPolicy	VM-memory allocator policy
MetricsFlushInterval	Resource-metering flush cadence
NumaSpanning	Global NUMA-spanning default
RamReservationPolicy	Host RAM reservation policy
SubnodePackingOrder	NUMA subnode packing order
AddTrustedIssuerCertificateHash / GetAuthCertificateHash	HGS/KP trusted issuer hashes, host auth cert

1.13. Other user-mode keys read

• HKLM\SYSTEM\CurrentControlSet\Services\HTTP\Parameters → MaxConnections (REG_DWORD) — vmms.exe for WinRM backing
• HKLM\SYSTEM\CurrentControlSet\Control\Network\Interfaces\{GUID}\Configuration — vmms.exe (vSwitch NIC config, REG_BINARY)
• HKLM\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Interfaces\{GUID} — vmms.exe (IP config)
• HKLM\SYSTEM\CurrentControlSet\Services\NetBT\Parameters\Interfaces\{GUID} — vmms.exe (NetBT config)
• HKLM\SYSTEM\CurrentControlSet\Control\StorVSP\PrefixMap\<prefix> — read by computecore.dll, vmchipset.dll!GetVirtualDiskPrefix and vmsynthstor.dll!SynthStorAttachment::Mount; maps disk prefix → device class GUID (fallback {f916c826-f0f5-4cd9-be68-4fd638cf9a53})
• HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management — vmcompute.exe (system memory tuning reads)

2. Registry — Kernel-Mode Drivers

All drivers read their tunables from HKLM\SYSTEM\CurrentControlSet\Services\<driver>\Parameters via RtlQueryRegistryValues / IoOpenDeviceRegistryKey unless noted.

2.1. VID (Virtual ID Driver) — vid.sys

Base key: HKLM\SYSTEM\CurrentControlSet\Services\vid\Parameters. Reader helpers: VidRegistryQueryUINT32[WithDefault] / …UINT64[WithDefault] / …Binary — called from the setup functions listed in the "Function" column.

ValueName	Type	Function	Purpose	Default
ForceSmallPages	REG_DWORD	VidDeviceAddVsmmLayerSetup	Force 4K GPA pages (no 2M/1G)	0
ForceZeroOnFree	REG_DWORD	VidDeviceAddVsmmLayerSetup	Zero guest pages on free	0
UsePoolForMbpArray	REG_DWORD	VidDeviceAddVsmmLayerSetup	Allocate MBP array from pool vs dedicated region	0
SkipSmallLocalAllocations	REG_DWORD	VidDeviceAddVsmmLayerSetup	Bypass small local-alloc path	1
FreezeTimeInModernStandby	REG_DWORD	VidDeviceAddVsmmLayerSetup	Freeze guest time during Modern Standby	1
ExoDeviceEnabled	REG_DWORD	VidExopRegKeyNotificationHandler	Expose \Device\VidExo partition API (Xbox/GameCore)	0
ExoDeviceEnabledClient	REG_DWORD	VidExopRegKeyNotificationHandler	Exo device accessible to non-admin clients	0
PageCombiningInterval	REG_DWORD	VsmmpRegQuery	Page-combining scan interval, sec (0 = off)	0
DaxRegularFileBackedEnabled	REG_DWORD	VsmmDaxFilepLockInputValidation	Allow regular-file-backed DAX MBP	0
MemoryReservePercentage	REG_DWORD	VsmmMemReservepQueryParametersPercentage	Top-level reserve percent	0
MemoryReserveAbove4GBOnly	REG_DWORD	VsmmMemReservepQueryParameters	Allocate reserve only above 4 GB	0
MemoryReserveHugePagesOnly	REG_DWORD	VsmmMemReservepQueryParameters	Reserve only 1 GB pages	0
HvPreDepositPagesPerGbMemory	REG_QWORD	VsmmHvpMemPreDepositRegistryQuery	HV pre-deposit pages per GB of host RAM	590
HvPreDepositPagesPerVp	REG_QWORD	VsmmHvpMemPreDepositRegistryQuery	HV pre-deposit pages per VP	20
HvMemWithdrawalMinPagesPerWorker	REG_QWORD	VsmmHvpMemPreDepositRegistryQuery	Min pages per HV mem-withdraw worker	0
HvMemWithdrawalProcessorCapFactor	REG_DWORD	VsmmHvpMemPreDepositRegistryQuery	Cap factor for HV mem-withdraw workers	0
IgnoreMemPart	REG_DWORD	VsmmMemPartSetupPhase0	Ignore memory-partition config	0
SoftRestartCount	REG_QWORD	VsmmHvMemPartpRegister	Persisted soft-restart generation	0
ForceDeferredCommit	REG_DWORD	VidPartitionIoctlSetup	Force deferred GPA commit	0
ForcePinBackingPages	REG_DWORD	VidPartitionIoctlSetup	Force pin of backing pages	0
FaultClusterSizeShift	REG_DWORD	VidPartitionIoctlSetup	Valid 0..15 — log2 of fault cluster size in pages (1 << N 4K pages = cluster size); written to partition flags bits 9-12	0
DirectMapFaultClusterSizeShift	REG_DWORD	VidPartitionIoctlSetup	Valid 0..15 — same log2-pages semantics but for direct-mapped regions; written to partition flags bits 13-16	0
PageBackingSize	REG_DWORD	VidPartitionIoctlSetup	Valid 0..2 — page backing class: 0 = default (4 KB), 1 = 2 MB huge page, 2 = 1 GB huge page; written to bits 0-1	0
ForcePageBackingSizeRequired	REG_DWORD	VidPartitionIoctlSetup	When non-zero, fails VM start if the requested PageBackingSize class is unavailable (bit 2 of field+32)	0
PageMappingSize	REG_DWORD	VidPartitionIoctlSetup	Valid 0..2 — page mapping class (granularity of GPA→SPA mapping entries, same 4K/2M/1G semantics); written shifted into bits 3-4	0
ForceSmallGpaMappings	REG_DWORD	VidPartitionIoctlSetup	Force small GPA mappings	0

HKLM\SYSTEM\CurrentControlSet\Services\vid\Parameters\MemoryReserve\<NUMA> — per-NUMA-node memory reserve:

ValueName	Type
SizeInMB	REG_QWORD
Percentage	REG_DWORD
IoSpaceSizeInMB	REG_QWORD

HKLM\SYSTEM\CurrentControlSet\Services\vid\Parameters\MemoryReserve\<partition> — per-partition reserve policy:

ValueName	Type	Default
HugePagesOnly	REG_DWORD	—
Above4GBOnly	REG_DWORD	—
UseSystemPartitionForHvDeposits	REG_DWORD	—
UseSystemPartitionForPhysicalBuffers	REG_DWORD	—
AllowSpillingForHvDeposits	REG_DWORD	—
AllowNumaSpanning	REG_DWORD	—
AllowPostKsrCreate	REG_DWORD	1
TargetSizeInMB	REG_QWORD	—

HKLM\SYSTEM\CurrentControlSet\Services\vid\Parameters\MemoryReserve\Primary\NumaIoSpaceDemotionCounts — REG_BINARY blob.

HKLM\SYSTEM\CurrentControlSet\Services\vid\Parameters\VirtStackMetadata\UseNonMirroredPartition — REG_DWORD.

Related keys outside vid's own service path — documented in §2.11 below (HKLM\SYSTEM\CurrentControlSet\Control\Hypervisor is shared between vid, hvloader and winhvr).

2.2. Hypervisor interface — winhv.sys / winhvr.sys / hvservice.sys / hvcrash.sys

winhv.sys has no direct registry reads — it is pure hypercall glue. All tuning goes via winhvr.sys (root-partition path).

Key	ValueName	Type	Driver	Function	Purpose	Default
HKLM\SYSTEM\CurrentControlSet\Control\Hypervisor	DfssEnabled	REG_DWORD	winhvr.sys	WinHvpInitializeXSchedulerSupport	Distributed Fair Share Scheduler gate (writes 0 if reg says 1 = disable)	1
HKLM\SYSTEM\CurrentControlSet\Services\hvservice (subkey path unresolved — static UNICODE_STRING in .rdata)	(2 values, names unresolved in decompilation: static UNICODE_STRINGs at binary offsets 0x7110 and 0x70C0)	REG_BINARY	hvservice.sys	HbEvtpSetLocalDiagnosticsEventSources → WinHvSetEventLogGranularSources	Two binary arrays: first-source-list and second-source-list parameters for granular ETW event-source control of the hypervisor log	-
HKLM\SYSTEM\CurrentControlSet\Services\hvcrash\Parameters	DebugFlags	REG_DWORD	hvcrash.sys	Diagnostics::Initialize (via WDF WdfRegistryQueryULong)	bit0 = DbgPrintOnError, bit1 = DbgBreakOnError	0

2.3. VMBus — vmbus.sys / vmbusr.sys / vmbkmcl.sys / vmbkmclr.sys / hvsocket.sys

Base key prefix: HKLM\SYSTEM\CurrentControlSet\Services\.

Key	ValueName	Type	Driver	Function	Purpose
HKLM\SYSTEM\CurrentControlSet\Services\vmbus\Parameters	RetryPostMessage	REG_DWORD	vmbusr.sys	DvReadRegistryValueUINT32	HvPostMessage retry count
HKLM\SYSTEM\CurrentControlSet\Services\vmbus\Parameters	AllowedDevicesWhenIsolated	REG_DWORD	vmbus.sys	XPartGetAllowedDevicesWhenIsolatedValue	Bitmask of VMBus device classes allowed when partition is isolated (default 0)
HKLM\SYSTEM\CurrentControlSet\Services\vmbus (device Parameters)	DedicatedProcessor	REG_DWORD	vmbus.sys / vmbusr.sys	VmbChannel setup	Dedicate processor to channel
HKLM\SYSTEM\CurrentControlSet\Services\vmbus (device interface)	InstanceGuid	REG_SZ	vmbus.sys	enum	Device-interface instance GUID
HKLM\SYSTEM\CurrentControlSet\Services\vmbus (device interface)	UserDefined	REG_SZ	vmbus.sys	enum	UserDefined subkey
HKLM\SYSTEM\CurrentControlSet\Services\vmbkmcl	ImagePath	REG_EXPAND_SZ	vmbkmcl.sys / vmbkmclr.sys	InitializeTelemetryAssertsKM	Client driver image path (telemetry-assert reporting)
HKLM\SYSTEM\CurrentControlSet\Services\vmbkmclr\Parameters	TraceLogPacketDelayThresholdSec	REG_DWORD	vmbkmclr.sys	KMCL trace-threshold init	VMBus packet-delay trace threshold (default 0 s)
HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Virtualization	AzureFeatureSet	REG_DWORD	hvsocket.sys	—	Enable Azure feature set
HKLM\SYSTEM\CurrentControlSet\Services\hvsocket (device interface)	LocalAddress	REG_SZ (GUID)	hvsocket.sys	Provider local address
HKLM\SYSTEM\CurrentControlSet\Services\hvsocket (device interface)	ParentAddress	REG_SZ (GUID)	hvsocket.sys	Provider parent address

2.4. Storage VSP/VSC — storvsp.sys / storvsc.sys / vhdmp.sys / vhdparser.sys / pvhdparser.sys / vmstorfl.sys

storvsp — HKLM\SYSTEM\CurrentControlSet\Services\storvsp. All values read in VspGetSettingsFromRegistry via helper VspGetRegistryUINT32, except OverrideParser/ServiceName (parser-registration subkeys, see below).

ValueName	Type	Purpose	Default
MaximumAdapterTransferSize	REG_DWORD	Cap on VSP adapter transfer	8 MB
WorkerCount	REG_DWORD	IO worker threads	-
WorkerIoCountPerWorker	REG_DWORD	Per-worker IO queue depth	-
MonitoredNotificationLatencyIn100ns	REG_DWORD	VMBus monitored-notification latency hint (capped at 10 000)	0
VirtualProcessorsPerChannel	REG_DWORD	VPs per StorVSP channel	-
SpreadWork	REG_DWORD	Spread IO work across NUMA-local threads	0
AffinitizeThreads	REG_DWORD	Pin worker threads (meaningful only if SpreadWork=1)	1
NominalIoTimeout	REG_DWORD	SCSI nominal IO timeout (sec)	10
QoSBurstSizePercent	REG_DWORD	Storage QoS burst %	-
FcVportRescanInterval (under <device> subkey)	REG_DWORD	FC vport rescan interval	-

Parser-registration keys (HKLM\SYSTEM\CurrentControlSet\Services\storvsp\Parameters\Parsers\{GUID}, read by storvsp.sys!ParserSystemLoadAndReferenceParserById / ParserSystemGetOverrideParserId): OverrideParser (REG_SZ, force specific parser GUID), ServiceName (REG_SZ, parser driver to load).

Parser map: HKLM\SYSTEM\CurrentControlSet\Control\StorVSP\Parsers\{GUID}: OverrideParser (REG_SZ), ServiceName (REG_SZ).

storvsc — HKLM\SYSTEM\CurrentControlSet\Services\storvsc\Parameters\Device: MultiPhaseResumeEnabled (DWORD), StorChannel (REG_BINARY container), ChannelCount (DWORD, 1-64), ChannelMask (REG_BINARY CPU affinity mask). Also reads HKLM\SYSTEM\CurrentControlSet\Control\CrashControl\MaximumTransferSize for dump path.

vhdmp — HKLM\SYSTEM\CurrentControlSet\Services\vhdmp\Parameters. Values split across three init paths: reload-safe values (VhdmpiUpdateDynamicGlobalPolicy) are marked (reload-safe) below; boot-time static values (VhdmpiInitializeGlobalPolicyData); CT-trace per-VHD values (VhdmpiCTLogInitVirtualDiskForTracing). Reader helpers: VhdmpiGetPolicyDWORD / VhdmpiGetPolicyBOOLEAN, CmRegUtilUcValueGetFullBuffer.

ValueName	Type	Default / Range	Purpose
InternalConcurrentMirrorThreadCount	REG_DWORD	2	LM mirror worker count (reload-safe)
MirrorBlockSize	REG_DWORD	0x800000 (8 MB)	Mirror copy block size (reload-safe)
InternalConcurrentMirrorMaxReaders	REG_DWORD	0	Mirror reader concurrency cap (reload-safe)
InternalConcurrentMirrorMaxWriters	REG_DWORD	0	Mirror writer concurrency cap (reload-safe)
EnableSMBCompression	REG_DWORD	0	Allow SMB compression during mirror (reload-safe)
EnableLiveMigrationIrpTagging	REG_DWORD	0	Tag live-migration mirror IRPs (reload-safe)
EnableRefsSparseMigration	REG_DWORD	1	Preserve ReFS sparse regions on migrate (reload-safe)
PreserveAbcSparseMigration	REG_DWORD	1	Preserve ABC sparse on migrate (reload-safe)
EnableFileSystemAttributeOverrides	REG_DWORD	1	Allow VHD-supplied FS attr overrides (reload-safe)
EnableExpansionNotification	REG_DWORD	0	Send disk-expanded notifications (reload-safe)
AlwaysAllowSparseFiles	REG_DWORD	0	Allow sparse backing files always (reload-safe)
CacheNodeQuota	REG_DWORD	256	Max VHD cache nodes (reload-safe)
SurfaceTimeout	REG_DWORD	300	VHD attach/surface watchdog (sec)
SurfaceBusScanPeriod	REG_DWORD	60	VHD bus re-scan period (sec)
ForceDisableTpSupport	REG_DWORD	0	Disable UNMAP/TP to backing
ForceEnableMegaTrim	REG_DWORD	0	Enable large-span TRIM
SectorSize	REG_DWORD	0	Override exposed sector size
IgnoreCrcFailures	REG_DWORD	bool	Ignore CRC failures (diag)
Vhd1PhysicalSectorSize4KB	REG_DWORD	bool	Report VHD1 as 4K physical sector
MinimumInternalOffloadReadSize	REG_DWORD	def 64 KB	Min size for internal offload read
VhdxNoDiskAndBlockSizeLimit	REG_DWORD	bool	Bypass VHDX disk/block size cap
VhdxCacheFlushTimeoutMs	REG_DWORD	def 5000	VHDX cache flush timeout
ForceDisableODX	REG_DWORD	bool	Force-disable ODX offload copy
ForceDisableTrim	REG_DWORD	bool	Force-disable UNMAP/TRIM
DisableReFSDuplicateExtents	REG_DWORD	bool	Disable ReFS duplicate-extent opt
DisableResiliency	REG_DWORD	bool	Disable resiliency
DisableVhdxMetadataResiliency	REG_DWORD	bool	Disable VHDX metadata resiliency
EnableSharedParentCaching	REG_DWORD	bool	Enable shared-parent cache
CachePagePriority	REG_DWORD	0..7 (CM_PAGE_PRIORITY)	Default 5 (normal), max 7 (highest)
SmbResiliencyTimeoutMs	REG_DWORD	1..300 000 ms	Out-of-range → reset to 60 000
CsvResiliencyTimeoutMs	REG_DWORD	1..300 000 ms	Out-of-range → reset to 180 000
CTUnblockStageServerTimeoutMs	REG_DWORD	200..300 000 ms	Out-of-range → reset to 700
IoSubTrackerCount	REG_DWORD	power-of-2 ≥ 1, def 128	IO sub-tracker count (non-power-of-2 values are invalid)
EnableAtomicWrites	REG_DWORD	bool	Enable atomic writes
RctMaximumDirtyCount	REG_DWORD	64	RCT max dirty
RctMaximumWrittenCount	REG_DWORD	120	RCT max written
RctMaximumFlushedCount	REG_DWORD	64	RCT max flushed
InternalConcurrentCopyThreadCount	REG_DWORD	1-8, def 4	Concurrent copy thread count
PrefetchDisable	REG_DWORD	bool	Disable VHDX prefetcher
CTTraceFlags	REG_DWORD	—	CT trace flags
CTTraceFilePath	REG_SZ	—	CT trace file path

vhdparser — HKLM\SYSTEM\CurrentControlSet\Services\vhdparser\Parameters: EnableVhdopDriver (REG_DWORD bool).

pvhdparser — HKLM\SYSTEM\CurrentControlSet\Services\pvhdparser\Parameters: RdssdToAbcMigration, FastPause, FastClose, IgnoreFlushes (all REG_DWORD bool). Also reads HKLM\SYSTEM\CurrentControlSet\Control\ComputerName\ComputerName\ComputerName.

vmstorfl — HKLM\SYSTEM\CurrentControlSet\Services\vmstorfl WDF Parameters: Enabled (REG_DWORD bool) — activate storage filter.

vdrvroot — HKLM\SYSTEM\CurrentControlSet\Services\vdrvroot\Parameters\FsDepends (subkey presence registers FS dependency).

2.5. Virtual Switch — vmswitch.sys (service key VmsMp)

Base: HKLM\SYSTEM\CurrentControlSet\Services\VmsMp\Parameters. Three init paths read this key:

• VmsReadReloadableParameters — runtime-reloadable values (batch-copy sizes, DPC thresholds, header counts). Re-read when the driver receives a parameter-reload signal.
• VmsReadGlobalParameters — driver-entry only (safe-header size, fatal OID error mode, execution mode).
• VmsQsReadUserConfig — VRSS scheduler tunables (queue-scheduling mode, expansion/coalescing periods, CPU load thresholds).

Reader helpers: VmsCsAttrValueReadULong, VmsCsAttrValueReadString.

ValueName	Type	Purpose
VmsVmNicDisableMediaIndication	REG_DWORD	Disable NIC media-status indications
VmsVmNicSendLmNetworkChangeIndication	REG_DWORD	Emit LM network-change indications
VmsBroadcastUplinkDisconnect	REG_DWORD	Broadcast uplink disconnect to vNICs
VmsBroadcastNetworkChangeStatusIndication	REG_DWORD	Broadcast network-change status
VmsBroadcastLinkSpeedChangeIndication	REG_DWORD	Broadcast link-speed change
VmsMaxPacketHeaderCount	REG_DWORD (≤12)	Max headers per NBL — minimum 0xC enforced (VmsReadReloadableParameters)
VmsBypassExtStack	REG_DWORD (bool)	Bypass extension stack
VmsMinFragmentOffset	REG_DWORD	Min fragment offset
VmsDisableUDPvRss	REG_DWORD (bool)	Disable UDP vRSS
VmsMaxNumberOfQueuesPerVPort	REG_DWORD	Max VMQ queues per vPort
VmsMinNumberOfQueuesPerVPort	REG_DWORD	Min VMQ queues per vPort
VmsVmNicMaxSendBufferSizeInMB	REG_DWORD	vNIC max send-buffer MB
VmsVmNicMaxSendShadowSizeInMB	REG_DWORD	vNIC max send-shadow MB
VmsVmExternalMdlShadowMode	REG_DWORD	External MDL shadow mode
VmsVmMaxBatchesPerFlush	REG_DWORD	Max batches per flush
VmsVmMaxNBLsPerFlush	REG_DWORD	Max NBLs per flush
VmsVmBatchCopyOnStackBatchSize	REG_DWORD (1-64)	On-stack batch-copy size
VmsVmBatchCopyLookAsideBatchSize	REG_DWORD (1-2048)	Look-aside batch size
VmsVmBatchCopyRndisBatchSize	REG_DWORD (1-1024)	RNDIS batch size
VmsSingleInstanceDpcLowThreshold	REG_DWORD (≤100)	Single-instance DPC-low threshold
VmsCumulativeDpcLowThreshold	REG_DWORD (≤100)	Cumulative DPC-low threshold
VmsMaxVrssQueueAllocatedMBytes	REG_DWORD	Max VRSS queue allocation MB
VmsAllowVersionQuery	REG_DWORD (bool)	Allow version query OID
VmsDefaultPtNicDropLowResourcesPackets	REG_DWORD (bool)	PT NIC drop low-resources packets
VmsMaxNicResetTimeInSeconds	REG_DWORD (10-600)	Max NIC reset time
VmsEnableHwTimestampOverVmbus	REG_DWORD (bool)	HW timestamp over VMBus
VmsMaxCtlAuditEntries	REG_DWORD	Max control audit entries
VmsLogRateLimitMaxCount	REG_DWORD	Log rate-limit max count
VmsMaxOutstandingDuplicateNblMBytes	REG_DWORD	Max outstanding duplicate NBL MB
VmsFatalOidErrorMode	REG_DWORD	0=ignore, 1=bugcheck, 2=log-only on fatal OID (VmsReadGlobalParameters; default 0)
VmsTokenRefundPeriodInMs	REG_DWORD	Token refund period ms
VmsLowLoadDurationInMs	REG_DWORD	Low-load duration ms
VmsCoalescingDurationInMs	REG_DWORD	Coalescing duration ms
VmsExpansionPeriodInMs	REG_DWORD	Queue expansion period ms
VmsNumberOfIndirectionTableEntries	REG_DWORD	RSS indirection table entries
VmsQueueSchedulingMode	REG_DWORD	VRSS scheduler: 0=static, 1=dynamic, 2=hybrid (VmsQsReadUserConfig; falls back to VmsVmqMode)
VmsExecutionMode	REG_DWORD	Bitmask: bit0=passive recv, bit3=passive send-complete (VmsReadGlobalParameters; default 0)
VmsSafeHeaderSize	REG_DWORD	Header-copy size, clamped to 0x100..VmsMaxSafeHeaderSize (default 256/384; VmsReadGlobalParameters)
VmsIsHypercopyEnabled	REG_DWORD (bool)	Hypercopy enabled
VmsVmNicDropOversizedSends	REG_DWORD (bool)	Drop oversized sends
VmsRequiredExtensionNotPresentDrop	REG_DWORD (bool)	Drop if required extension absent
VmsPtNicSendMinStackThresholdInBytes	REG_DWORD	PT NIC send min-stack threshold
VmsIsRscOverVmBusEnabled	REG_DWORD (bool)	RSC over VMBus
VmsHostNicIndicateNblsInline	REG_DWORD (bool)	Host NIC inline NBL indication
VmsNetEventPausePtNicDrop	REG_DWORD (bool)	Net-event pause drop on PT NIC
VmsSwitchRssSendPacketCountMultiplier	REG_DWORD	Switch RSS send-count multiplier
VmsMaxNumMoveToken	REG_DWORD	Max move-token count
VmsCpuLoadLowerThreshold	REG_DWORD	CPU load lower threshold
VmsCpuLoadUpperThreshold	REG_DWORD	CPU load upper threshold
VmsSendInterruptMode	REG_DWORD	Send interrupt mode
VmsDiagnosticFlags	REG_DWORD	Diagnostic flags

HKLM\SYSTEM\CurrentControlSet\Services\VmsMp\Parameters\Switches\<id>\Properties — per-switch extension properties (no fixed value schema).

HKLM\SYSTEM\CurrentControlSet\Services\VmsMp\Parameters\Nics\<id> — per-NIC persistent state:

ValueName	Type
NicType	REG_DWORD (1 = external, 2 = vNIC)
SwitchName	REG_SZ
PortName	REG_SZ
FriendlyName	REG_SZ
OriginalName	REG_SZ
MiniportDeviceGuid	REG_SZ
NicCurrentMacAddress	REG_BINARY (6 bytes)
NicPermanentMacAddress	REG_BINARY (6 bytes)
IsLightWeightNic	REG_DWORD
IsLightWeightNicEnable	REG_DWORD

Per-NIC device SW key (via IoOpenDeviceRegistryKey): VlanID (0-4095).

Also reads HKLM\SYSTEM\CurrentControlSet\Control\ComputerName\ComputerName\ComputerName.

2.6. vPCI / DDA — pcip.sys

Per-device SW key (opened via WDF WdfDeviceOpenRegistryKey, read in InitializeMitigationMaps with WdfRegistryQueryULong). PCIPHackFlags is the only actual Reg* read — the other three values are consumed via PnP/WDF property facilities, not direct registry calls.

ValueName	Type	Purpose	Default
PCIPHackFlags	REG_DWORD	DWORD bitmask to disable / alter individual config-space mitigations for a DDA function	0
SupportedDevice	REG_DWORD	Mark device supported for vPCI passthrough	0
HotRemoveSafe	REG_DWORD	Declared hot-remove-safe	0
DisablePowerManagement	REG_DWORD	Disable PM on passthru device	0

2.7. Video — HyperVideo.sys

Base key: HKLM\SYSTEM\CurrentControlSet\Services\Video\Virtualization. All values read in a single function — HvdDdiAddDevice — using RtlQueryRegistryValuesEx with a RtlQueryRegistryValues fallback.

ValueName	Type	Purpose	Default
MonitorCount	REG_DWORD	Mode count (1=single, 2=dual, 3=auxiliary) — controls which of the other values are consulted	1
HorizontalSizeInCm	REG_DWORD	Physical horizontal monitor size	0
VerticalSizeInCm	REG_DWORD	Physical vertical monitor size	0
InternalDisplay	REG_DWORD (bool)	Mark display as internal (affects brightness/DDC)	0
VirtualModeSupport	REG_DWORD	Expose EDID-less virtual modes (gated by MonitorCount==1)	1 when MonitorCount≥2
HorizontalResolution	REG_DWORD (≥100, even)	Primary horizontal pixel resolution	1024
VerticalResolution	REG_DWORD	Primary vertical pixel resolution	768
MaskWidth	REG_DWORD	Mask/bezel width between dual displays (MonitorCount≥2)	-
HorizontalResolutionAuxiliary	REG_DWORD (≥100)	Aux display horizontal resolution (MonitorCount==3)	1024
VerticalResolutionAuxiliary	REG_DWORD	Aux display vertical resolution	-

2.8. Keyboard — hyperkbd.sys

Reads HKLM\SYSTEM\CurrentControlSet\Services\hyperkbd\Parameters\crashdump subkey (KbdConnectData etc.) and HKLM\SYSTEM\CurrentControlSet\Services\kbdclass\Parameters as companion (used during crash-dump path). Driver itself has no RtlQueryRegistryValues / ZwQueryValueKey calls — config comes from the driver INF and WDF defaults.

2.9. Windows Container FS filter — wcifs.sys

Base key: HKLM\SYSTEM\CurrentControlSet\Services\wcifs\Parameters (opened via IoOpenDriverRegistryKey in WcSetConfiguration), plus a boot-config subkey under HKLM\SYSTEM\CurrentControlSet\Control resolved in WcSetBootConfiguration at driver entry.

ValueName	Type	Function	Purpose	Default
DebugOptions	REG_DWORD (bitmask)	wcifs:WcSetConfiguration	Per-bit diagnostic toggles (IRP trace, reparse/tombstone/placeholder/layering debug)	0
BootContainer	REG_SZ / REG_BINARY	wcifs:WcSetBootConfiguration	Identifies the boot container the system came up in	not-present (host)
BootContainerGuid	REG_SZ (GUID)	wcifs:WcSetBootConfiguration	GUID of boot container; selects the per-GUID sub-hive	not-present
Hvsi	REG_DWORD / REG_SZ	wcifs:WcSetBootConfiguration	Flag: container is an HVSI (Hyper-V Isolated) container; changes isolation path	0
WCIFSContainerMode	REG_DWORD	wcifs:WcSetBootConfiguration	Container layering mode (silo / nested / boot)	0
InstanceName	REG_SZ	wcifs:WcSetBootConfiguration	Filter-manager instance name when mounting boot container	-
ReparseTag	REG_DWORD	wcifs:WcSetBootConfiguration	Reparse-point tag honored by the filter (IO_REPARSE_TAG_WCI_1, …_WCI_TOMBSTONE)	0x8000001B

2.10. Drivers WITHOUT driver-specific registry config

These Hyper-V kernel drivers have no RtlQueryRegistryValues / ZwQueryValueKey / IoOpenDeviceRegistryKey calls against their own service key — all behavior is driven by the VMBus channel state or IOCTLs from vmms.exe:

dmvsc.sys, vmgencounter.sys, vmgid.sys, vmsvcext.sys, lunparser.sys, NdisVirtualBus.sys, VmsProxy.sys, VmsProxyHNic.sys, hvsocketcontrol.sys, passthruparser.sys, vpcivsp.sys (DDA VSP backend), VMBusHID.sys.

ramparser.sys and vmbusproxy.sys link a shared PnP helper that reads generic device-creation settings (Security, DeviceType, DeviceCharacteristics, Exclusive) from HKLM\SYSTEM\CurrentControlSet\Control\Class\{ClassGUID}\Properties — these are not driver-specific tunables, just the standard PnP stack defaults.

2.11. Hypervisor boot parameters

Hyper-V hypervisor is launched by hvloader.dll during Windows boot. Its configuration comes from two layers merged at launch:

1. BCD options under the {hypervisorsettings} object — set via bcdedit /set {hypervisorsettings} NAME value.
2. Registry fallback under HKLM\SYSTEM\CurrentControlSet\Control\Hypervisor — key opened by hvloader!HvlLoadHypervisor via OslGetControlSubkey. When a BCD option is absent, hvloader tries the registry value with the same name (OslGetValueAtKey,OslGetStringValueAtKey).

hvix64.exe / hvax64.exe (the actual hypervisor images) do not read BCD or registry themselves — they receive the resolved configuration as a data structure passed by hvloader.

2.11.1. HKLM\SYSTEM\CurrentControlSet\Control\Hypervisor values

All values here are read by hvloader.dll (boot-time). Entries marked (bcdedit) are also settable via BCD on the {hypervisorsettings} object — the registry value serves as fallback if the BCD element is not set.

ValueName	Type	Possible values	Default (absent)	Purpose
IgnoreMemPart	REG_DWORD	0, non-zero	0	Skip memory-partition metadata init (bypasses NUMA/memory-reserve partitioning); consulted both by hvloader and by vid.sys as a global override
HypervisorUseVapic	REG_DWORD (bcdedit)	0 = disabled, non-zero = enabled	0	Enable hardware virtual APIC (X2APIC/AVIC when available); sets low bit of flags word; BCD fallback for boolean element 0x260000D6
DmaGuardOptIn	REG_DWORD	0, 1	0	Opt-in flag for DMA-Guard IOMMU protection during boot; affects early DMA mapping policy
EnableHardwareIsolation	REG_DWORD	0 = default, 1 = enable, 2 = force	0	Enable hardware-isolation CPU features (Intel TDX / AMD SEV-SNP container mode); 1 → normal, 2 → required
EnableSevSnp	REG_DWORD	0 = disabled, non-zero = enabled	0	Enable AMD SEV-SNP isolation (checked only on AMD "AuthenticAMD" CPUID — ignored otherwise)
EnableIov	REG_DWORD	0 = disabled, non-zero = enabled	0	Enable IOV (IOMMU virtualization) for device assignment at boot
InitialAllocationNumaPolicy	REG_DWORD	1 = distributed, 2 = packed	2	Initial NUMA allocation policy for host memory; also controlled via the NUMADISTRIBUTED token in Hypervisorloadoptions
hypervisorperfmon	REG_SZ (bcdedit)	"system", "hypervisor"	—	Owner of performance-monitoring hardware: "system" = OS kernel owns PMU (bit 0x80000), "hypervisor" = HV owns PMU (bit 0x100000); also settable as BCD integer 0 / 1
Hypervisorloadoptions	REG_SZ (bcdedit)	free-form token string	—	Additional boot tokens parsed via strstr. Known tokens: " ENABLEHARDWAREISOLATION ", " NUMADISTRIBUTED "

Subkey MetadataMemoryPartition — read if IgnoreMemPart is zero:

ValueName	Type	Purpose
Name	REG_SZ	Name/identifier of the metadata memory partition used for HV deposits

2.11.2. HKLM\SYSTEM\CurrentControlSet\Services\winhvr\Parameters

One DWORD, consulted only when the active hypervisor scheduler is the Root scheduler (scheduler type = 4); ignored otherwise.

ValueName	Type	Possible values	Default	Purpose
DisableDynamicFairShareScheduler	REG_DWORD	0 = DFSS enabled, non-zero = disabled	0 (DFSS on)	Read in winhvr!WinHvpInitializeXSchedulerSupport: when set non-zero and root scheduler active, turns off Dynamic Fair Share Scheduler for root partition VPs (flag WinHvpDfssEnabled)

2.11.3. Relevant BCD options (bcdedit /set {hypervisorsettings} …)

The HvlLoadHypervisor function reads 13+ BCD elements on the boot OS-loader object. The canonical options, as publicly documented by Microsoft, are below (hvloader performs integer/boolean lookups on the OS-loader object via BlGetBootOptionInteger / BlGetBootOptionBoolean using numeric element IDs in the hypervisor integer range 0x25000018..0x25000055 and boolean range 0x26000011..0x260000D6):

bcdedit name	Type	Possible values	Purpose
hypervisorlaunchtype	enum	Off, Auto	Master on/off for Hyper-V at boot
hypervisordebug	bool	Yes/No	Enable hypervisor kernel debugger
hypervisordebugtype	enum	Serial, 1394, Net	Debug transport
hypervisorbaudrate	int	serial baud (e.g. 115200)	Debug serial baud rate
hypervisorchannel	int	0-62	1394/NET channel
hypervisorserialdebugport	int	COM port number	Debug serial port (COM1=1, COM2=2, …)
hypervisorbusparams	string	b.d.f (bus.dev.func)	PCI bus/device/function of debug NIC
hypervisorhostip	int (IP4)	IPv4 as 32-bit int	Net-debug host IP
hypervisorhostport	int	TCP port	Net-debug host port
hypervisornumproc	int	1..N	Limit number of LPs the hypervisor uses
hypervisorrootproc	int	1..N	Number of root-partition VPs (dedicated-scheduler mode)
hypervisorrootprocpercore	int	SMT units	Root VPs per physical core
hypervisoriommupolicy	enum	Default, Enable, Disable	IOMMU usage policy
hypervisorloadoptions	string	token list	Free-form tokens (mirrored in Hypervisorloadoptions registry value)
hypervisorscheduler	enum	Classic=1, Core=2, Root=3 (also 4=legacy root, seen in winhvr)	Hypervisor scheduler type
hypervisorusevapic	bool	Yes/No	Use virtual APIC (mirrors HypervisorUseVapic reg value)
hypervisorperfmon	enum	System, Hypervisor	Owner of PMU hardware (mirrors reg value)
hypervisordisableslat	bool	Yes/No	Disable SLAT (EPT/NPT) — forces shadow paging, debug-only
hypervisoruselargevtlb	bool	Yes/No	Use large virtual-TLB
hypervisorenforcedcodeintegrity	bool	Yes/No	Enforce HV-level code integrity
hypervisordisabledfss	bool	Yes/No	BCD counterpart of the DisableDynamicFairShareScheduler reg value

Values for hypervisorscheduler are reported back to the root partition via WinHvGetSystemInformation(SystemHypervisorInformation) as a uint32. The root scheduler is selected via value 4.

3. Group Policy / MDM Policies

3.1. HKLM\SOFTWARE\Policies\Microsoft\Windows\HyperV

Read by vmms.exe via Vml::VmRegistryKey::Open. The only Hyper-V-specific policy key (everything else under Policies\Microsoft\Windows\* is consumed by ntoskrnl / rpcrt4 / vmcompute, not Hyper-V role itself).

ValueName	Type	Purpose
RequireSecureDeviceAssignment	REG_DWORD	Block DDA of devices that are not DMA-remap-secure. Error: "Device is not compliant with HyperV\RequireSecureDeviceAssignment group policy."
RequireSupportedDeviceAssignment	REG_DWORD	Block DDA of devices not on the supported/allow-list. Error: "Device is not compliant with HyperV\RequireSupportedDeviceAssignment group policy."

3.2. HKLM\SOFTWARE\Policies\Microsoft\Windows\CredentialsDelegation

Read by both vmms.exe and Microsoft.Virtualization.Client.dll. vmms also writes here (CredSSP SPN allow-lists under subkeys 1..N).

• Client reads RestrictedRemoteAdministration (REG_DWORD).
• vmms.SmbPolicyManager adds the VM-host SPN to AllowFreshCredentials and AllowFreshCredentialsWhenNTLMOnly for CredSSP live-migration.

3.3. Not present

• No HKLM\SOFTWARE\Policies\Microsoft\Windows\WindowsUpdate references in Hyper-V binaries (hits belong to ntoskrnl / rpcrt4).
• No HKLM\SOFTWARE\Microsoft\PolicyManager (MDM bridge) references. Hyper-V is classic-GPO-only.

4. WMI Schema (root\virtualization\v2)

Sources: WindowsVirtualization.V2.mof (4405 lines), WindowsHyperVCluster.V2.mof (2230 lines, root\HyperVCluster\v2), HgsClientWmi.mof (HGS client). Provider: VmmsWmiInstanceAndMethodProvider (in-process inside vmms.exe).

Association classes (e.g. Msvm_HostedService, Msvm_ElementSettingData) intentionally omitted — they just link instances and carry no config surface.

4.1. Core VM / Compute System

Msvm_ComputerSystem (extends CIM_ComputerSystem) — a live or stored VM.

• OnTimeInMilliseconds (uint64) — uptime since start
• ProcessID (uint32) — worker (vmwp) PID
• TimeOfLastConfigurationChange (datetime)
• NumberOfNumaNodes (uint16)
• ReplicationState / ReplicationHealth / ReplicationMode (uint16, ValueMaps)
• LastSuccessfulBackupTime (datetime)
• EnhancedSessionModeState (uint16, {2,3,6})
• HwThreadsPerCoreRealized (uint32)
• ManagementVtlImageVersion / ManagementVtlImageFileName (string)
• Methods: RequestStateChange, RequestReplicationStateChange, InjectNonMaskableInterrupt, InjectNonMaskableInterruptEx(Vtl), RequestCustomRestore

Msvm_PlannedComputerSystem — staging VM during import/migration.

• AssignedNumaNodeList[] (uint16, Indexed), OnTimeInMilliseconds (uint64)

Msvm_VirtualSystemSettingData — editable VM settings blob.

• Identity: BIOSGUID, BIOSSerialNumber, BaseBoardSerialNumber, ChassisSerialNumber, ChassisAssetTag, VirtualSystemIdentifier
• Arch/gen: Architecture {"x64","arm64"}, VirtualSystemSubType {Microsoft:Hyper-V:SubType:1|2}, Version
• Boot: BootOrder[] (MAX 4), BootSourceOrder[], BootPciExpress + BootPciExpressInstanceFilter, NetworkBootPreferredProtocol {IPv4,IPv6}, SecureBootEnabled + SecureBootTemplateId, PauseAfterBootFailure, BIOSNumLock
• Memory/MMIO: LowMmioGapSize, HighMmioGapSize, HighMmioGapBase, EnableHibernation
• Debug: DebugChannelId, DebugPort, DebugPortEnabled {Off|On|OnAutoAssigned}
• Snapshots/state: UserSnapshotType {2,3,4,5}, IsAutomaticSnapshot, AutomaticSnapshotsEnabled, IsSaved, IncrementalBackupEnabled, GuestStateDataRoot, GuestStateFile, SourceGuestStateFile
• NUMA/SLIT: VirtualNumaEnabled, NumaNodeTopologyArray[], VirtualSlitType {None|Firmware|Measured|FirmwareFallbackMeasured}
• VTL2: Vtl2AddressRangeBase, Vtl2AddressRangeSize, Vtl2MmioAddressRangeSize, Vtl2AddressSpaceConfigurationMode {Default|ConfigurableSizePlacement|ExplicitPlacement}
• Isolation: GuestStateIsolationEnabled, GuestStateIsolationType {0,1,2,3,16,18,19}, GuestStateIsolationMode {0,1,2}
• Misc: AdditionalRecoveryInformation, AllowFullSCSICommandSet, TurnOffOnGuestRestart, ConsoleMode {Default|COM1|COM2|None}, EnhancedSessionTransportType {0,1}, AutomaticCriticalErrorAction {None|"Pause Resume"}, AutomaticCriticalErrorActionTimeout (interval), LockOnDisconnect, GuestControlledCacheTypes, ClusterWideNodeCapabilitiesValidationMode {Default|Override}, VMBusMessageRedirection {0,1}, WorkerJobObjectName, MemoryHostingJobObjectName, FirmwareFile + FirmwareParameters[], WatchdogEnabled, GuestFeatureSet (uint64), ManagementVtlUpdatePolicy, AllowReducedFcRedundancy

Msvm_SummaryInformation / Msvm_SummaryInformationBase — UI-listing view (Name, State, CPU%, Memory, Uptime).

4.2. Processor & Memory

Msvm_Processor (CIM_Processor) — virtual CPU.

Msvm_ProcessorSettingData (CIM_ResourceAllocationSettingData):

• Topology: HwThreadsPerCore, MaxProcessorsPerNumaNode, MaxNumaNodesPerSocket, MaxProcessorCountPerL3, MaxClusterCountPerSocket, EnableSocketTopology
• Features/compat: LimitCPUID, LimitProcessorFeatures, LimitProcessorFeaturesMode {DefaultMinimumFeatures|ClusterNodeCommonFeatures}, ProcessorFeatureSet, CpuBrandString, EnlightenmentSet
• Host protection/nested: EnableHostResourceProtection, ExposeVirtualizationExtensions, ExtendedVirtualizationExtensions {HardwareIsolation}, MaxHwIsolatedGuests
• Hierarchical: EnableHierarchicalVirtualization, MaxHierarchicalPartitions, MaxHierarchicalVps
• Perfmon: EnablePerfmonPmu, EnablePerfmonArchPmu, EnablePerfmonLbr, EnablePerfmonPebs, EnablePerfmonIpt
• Diagnostic buffers: PartitionDiagnosticBufferCount, PartitionDiagnosticBufferSizeInPages
• APIC / paging: ApicMode {0..3}, EnableLegacyApicMode, EnablePageShattering {0,1,2}, AllowACountMCount, HideHypervisorPresent, DisableSpeculationControls
• CPU groups / caps: CpuGroupId, PerfCpuFreqCapMhz, L3CacheWays, L3ProcessorDistributionPolicy {SmallToLarge|LargeToSmall|EvenSmallToLarge|EvenLargeToSmall}, PhysicalAddressWidth

Msvm_ProcessorPool (CIM_ResourcePool) — method CalculatePossibleReserve(ProcessorCount).

Msvm_NumaNode, Msvm_NumaNodeTopology, Msvm_ElementAllocatedFromNumaNode.

Msvm_Memory (CIM_Memory) — VM memory device.

Msvm_MemorySettingData (CIM_ResourceAllocationSettingData):

• DynamicMemoryEnabled, TargetMemoryBuffer
• IsVirtualized, SwapFilesInUse
• MaxMemoryBlocksPerNumaNode
• SGX: SgxEnabled, SgxSize, SgxLaunchControlMode {0,1,2}, SgxLaunchControlDefault
• Pages: HugePagesEnabled, BackingType {0,1,2}, BackingPageSize {0,1,2}, EnableHotHint, EnableColdHint, EnableEpf, EnablePrivateCompressionStore
• Crypto/tracking: MemoryEncryptionPolicy {0,1,2}, MemoryAccessTrackingPolicy, MemoryAccessTrackingState

4.3. Storage

Msvm_VirtualHardDiskSettingData — VHD/VHDX template.

• Type {2,3,4} (Fixed/Dynamic/Differencing)
• Format {2,3,4} (Unknown/VHD/VHDX)
• Path, ParentPath, ParentIdentifier, ParentTimestamp
• MaxInternalSize, BlockSize, LogicalSectorSize, PhysicalSectorSize
• VirtualDiskId
• IsPmemCompatible, PmemAddressAbstractionType, DataAlignment

Msvm_VirtualHardDiskState — read-only: FileSize, InUse, MinInternalSize, PhysicalSectorSize, Alignment, FragmentationPercentage, Timestamp.

Msvm_VHDSetInformation (.vhds AVHDX sets) — Path, SnapshotIdList[], AllPaths[].

Msvm_VHDSnapshotInformation — FilePath, SnapshotId, SnapshotPath, ParentPathsList[], CreationTime, ResilientChangeTrackingId.

Msvm_ImageManagementService — methods: CreateVirtualHardDisk, GetVirtualHardDiskSettingData, GetVirtualHardDiskState, ResizeVirtualHardDisk, MergeVirtualHardDisk, OptimizeVirtualHardDisk, AttachVirtualHardDisk, GetVHDSnapshotInformation.

Msvm_StorageJob (CIM_ConcreteJob), Msvm_MountedStorageImage, Msvm_DiskDrive, Msvm_DVDDrive, Msvm_DisketteDrive, Msvm_LogicalDisk, Msvm_StorageAllocationSettingData, Msvm_SCSIProtocolController, Msvm_IDEController, Msvm_DisketteController, Msvm_PersistentMemoryController, Msvm_StorageSettingData, Msvm_VirtualLogicalUnitSettingData.

4.4. Networking — vSwitch / vNIC

Msvm_VirtualEthernetSwitch — vSwitch instance. MaxVMQOffloads (uint32), MaxIOVOffloads (uint32, read-only).

Msvm_VirtualEthernetSwitchSettingData — IOVPreferred=FALSE, ExtensionOrder[], BandwidthReservationMode {0..3}, PacketDirectEnabled, TeamingEnabled, AllowNetLbfoTeams, BypassExtensionStack, RequiredExtensionIds[].

Msvm_VirtualEthernetSwitchManagementService — methods: DefineSystem, DestroySystem, ModifySystemSettings, AddResourceSettings, ModifyResourceSettings, RemoveResourceSettings, AddFeatureSettings, ModifyFeatureSettings, RemoveFeatureSettings.

Msvm_VirtualEthernetSwitchManagementCapabilities — IOVSupport, IOVSupportReasons[], AsynchronousMethodsSupported[].

Msvm_EthernetSwitchPort — VMQOffloadUsage, IOVOffloadUsage.

Msvm_EthernetPortAllocationSettingData — vNIC binding: EnabledState, LastKnownSwitchName, RequiredFeatures[], TestReplicaPoolID, TestReplicaSwitchName, CompartmentGuid, PortName.

Msvm_ExternalEthernetPort / InternalEthernetPort / EmulatedEthernetPort / SyntheticEthernetPort — port flavors.

Msvm_SyntheticEthernetPortSettingData, Msvm_EmulatedEthernetPortSettingData — NIC RASDs.

Per-port feature settings (VFP extensions):

Class	Key properties
Msvm_EthernetSwitchPortAclSettingData	Name, Direction, Applicability, AclType, Action, LocalAddress, RemoteAddress, PrefixLength
Msvm_EthernetSwitchPortExtendedAclSettingData	Name, Direction, Action, LocalIP/RemoteIP/LocalPort/RemotePort/Protocol (default "ANY"), Weight, Stateful, IdleSessionTimeout=255, IsolationID
Msvm_EthernetSwitchPortSecuritySettingData	AllowMacSpoofing, EnableDhcpGuard, EnableRouterGuard, MonitorMode, MonitorSession, AllowIeeePriorityTag, VirtualSubnetId (max 16777215), AllowTeaming, TeamName, TeamNumber, StormLimit, DynamicIPAddressLimit, EnableFixSpeed10G
Msvm_EthernetSwitchPortOffloadSettingData	IPSecOffloadLimit=512, VMQOffloadWeight=100, IOVOffloadWeight, IOVQueuePairsRequested=1, IOVInterruptModeration {Default
Msvm_EthernetSwitchPortRdmaSettingData	RdmaOffloadWeight
Msvm_EthernetSwitchPortTeamMappingSettingData	NetAdapterName, NetAdapterDeviceId, DisableOnFailover
Msvm_EthernetSwitchPortVlanSettingData	OperationMode {1,2,3}, AccessVlanId, NativeVlanId, PvlanMode {1,2,3}, PrimaryVlanId, SecondaryVlanId, PruneVlanIdArray[], TrunkVlanIdArray[], SecondaryVlanIdArray[]
Msvm_EthernetSwitchPortIsolationSettingData	isolation config
Msvm_EthernetSwitchPortBandwidthSettingData	bandwidth
Msvm_EthernetSwitchPortRoutingDomainSettingData	NV-GRE routing
Msvm_EthernetSwitchPortProfileSettingData	port profile

Switch-level features: Msvm_VirtualEthernetSwitchBandwidthSettingData, Msvm_VirtualEthernetSwitchNicTeamingSettingData, Msvm_EthernetSwitchHardwareOffloadSettingData.

Extensions: Msvm_EthernetSwitchExtension, Msvm_InstalledEthernetSwitchExtension.

Live metrics: Msvm_EthernetSwitchPortOffloadData, Msvm_EthernetSwitchPortBandwidthData.

Fibre Channel: Msvm_VirtualFcSwitch / Msvm_VirtualFcSwitchSettingData, Msvm_ExternalFcPort / SyntheticFcPort / FcSwitchPort, Msvm_FcPortAllocationSettingData, Msvm_SyntheticFcPortSettingData.

4.5. Security / Shielding / TPM

Msvm_SecuritySettingData (all Required, Read): TpmEnabled, KsdEnabled, ShieldingRequested, DataProtectionRequested, EncryptStateAndVmMigrationTraffic, VirtualizationBasedSecurityOptOut, BindToHostTpm, AppContainerLaunchOptOut.

Msvm_SecurityElement — runtime: Shielded, EncryptStateAndVmMigrationTrafficEnabled.

Msvm_SecurityService — methods: ModifySecuritySettings, SetSecurityPolicy, SetKeyProtector, GetKeyProtector, RestoreLastKnownGoodKeyProtector.

Msvm_TPM — virtual TPM device.

MSFT_HgsClientConfiguration (HGS client, MSFT_ prefix): Mode {0,1,2}, IsHostGuarded, KeyProtectionServerUrl, AttestationServerUrl, AttestationOperationMode, AttestationStatus, AttestationSubstatus, FallbackKeyProtectionServerUrl[], FallbackAttestationServerUrl[], LastKeyProtectionServerUrl, LastAttestationServerUrl. Methods: Get, IsHostTrusted, SetByChangeToLocalMode, SetBySecureHostingServiceMode.

MSFT_HgsGuardian — Name, SigningCertificate[], EncryptionCertificate[], EncryptionCertificateSignature, EncryptionCertificateSignatureAlgorithm, HasPrivateSigningKey, GuardianMetadataVersion. Methods: NewByAcceptCertificates, NewByCertificateThumbprints, NewByGenerateCertificates, Import, Export, Remove.

MSFT_HgsKeyProtector — Owner, Guardians[], RawData[]. Methods: NewByGuardians, Grant, Revoke, ConvertToByRawBytes.

MSFT_HgsKeyProtectorOperations — UnwrapKeyProtector, CreateKeyProtector, EncryptDataWithKeyProtector, DecryptDataWithKeyProtector.

4.6. Devices — DDA / GPU / Flex-IO

Msvm_AssignableDeviceService, Msvm_AssignableDeviceDismountSettingData, Msvm_PciExpress, Msvm_PciExpressSettingData.

Msvm_GpuPartition — DeviceInstancePath, PartitionId, PartitionVfLuid, CurrentCompute / Decode / Encode / VRAM, SupportsOutgoingLiveMigration.

Msvm_PartitionableGpu — host GPU: ValidPartitionCounts[], PartitionCount, TotalVRAM, AvailableVRAM, SupportsIncomingLiveMigration, Min/Max/OptimalPartitionVRAM, …Encode, …Decode, …Compute.

Msvm_GpuPartitionSettingData — per-VM: Min/Max/OptimalPartitionVRAM, …Encode, …Decode, …Compute, VirtualSystemIdentifiers[], NumaAwarePlacement.

Msvm_FlexIoDevice, Msvm_FlexIoDeviceSettingData — generic PCIe flex-IO.

Msvm_SyntheticDisplayController, Msvm_SyntheticDisplayControllerSettingData, Msvm_S3DisplayController, Msvm_Synthetic3DDisplayController, Msvm_Synthetic3DService, Msvm_Synth3dVideoPool, Msvm_PhysicalGPUInfo, Msvm_Physical3dGraphicsProcessor — video/RemoteFX.

Msvm_Keyboard / Ps2Mouse / SyntheticKeyboard / SyntheticMouse.

Msvm_SerialController, Msvm_SerialPort, Msvm_SerialPortSettingData.

Msvm_Battery, Msvm_BatterySettingData.

Msvm_TerminalService, Msvm_TerminalServiceSettingData, Msvm_TerminalConnection, Msvm_InteractiveSessionACE — VMConnect plumbing.

4.7. Integration Services (Guest components)

Each IC is a pair (component + SettingData):

• HeartbeatComponent + SettingData
• KvpExchangeComponent + SettingData, plus Msvm_KvpExchangeDataItem (Name/Data/Source) for host↔︎guest KVP
• ShutdownComponent + SettingData
• TimeSyncComponent + SettingData
• VssComponent + SettingData, plus Msvm_VssService
• RdvComponent + SettingData (RDP / Enhanced Session)
• GuestServiceInterfaceComponent + SettingData
• Msvm_GuestService, Msvm_GuestCommunicationService, Msvm_GuestFileService (Copy-VMFile), Msvm_CopyFileToGuestSettingData, Msvm_CopyFileToGuestJob
• Msvm_GuestClusterInformation — embedded guest cluster state
• Msvm_GuestNetworkAdapterConfiguration — IP/DNS/VLAN info for in-guest NIC

4.8. Migration / Replication / Snapshots

• Msvm_VirtualSystemMigrationService — live migration. Methods: MigrateVirtualSystemToHost, MigrateVirtualSystemToHostEx, CheckCapabilities
• Msvm_VirtualSystemMigrationServiceSettingData — host config (enabled, auth type Kerberos/CredSSP, max simultaneous)
• Msvm_VirtualSystemMigrationSettingData — per-migration (destination, transfer type, network list)
• Msvm_VirtualSystemMigrationNetworkSettingData — SubnetNumber, PrefixLength, Metric, Tags
• Msvm_VirtualSystemMigrationCapabilities, Msvm_MigrationJob, Msvm_MoveUnmanagedVhd
• Msvm_ReplicationService, Msvm_ReplicationRelationship, Msvm_ReplicationSettingData, Msvm_ReplicationServiceSettingData, Msvm_ReplicationAuthorizationSettingData, Msvm_ReplicationStatistics, Msvm_ReplicationProvider
• Msvm_FailoverNetworkAdapterSettingData — IP injection on failover
• Msvm_VirtualSystemSnapshotService, Msvm_VirtualSystemSnapshotSettingData, Msvm_VirtualSystemReferencePointService, Msvm_VirtualSystemReferencePoint, Msvm_VirtualSystemReferencePointSettingData, Msvm_DiskMergeSettingData

4.9. Collections (VM Groups)

• Msvm_CollectionManagementService, Msvm_VirtualSystemCollection, Msvm_ManagementCollection, Msvm_CollectionSettingData
• Msvm_CollectionSnapshotService, Msvm_SnapshotCollection, Msvm_CollectionSnapshotExportSettingData
• Msvm_CollectionReferencePointService, Msvm_ReferencePointCollection, Msvm_CollectionReferencePointSettingData, Msvm_CollectionReferencePointExportSettingData, Msvm_CollectionReferencePointExportJob
• Cluster-only: Msvm_CollectionReplicationService, Msvm_CollectionReplicationSettingData, Msvm_CollectionReplicationStatistics, Msvm_CollectionRecoveryPoint, Msvm_SharedDiskSetReplicationRelationship

4.10. Management / Host Service

Msvm_VirtualSystemManagementService — main VMMS façade. Methods: DefineSystem, DestroySystem, ModifySystemSettings, AddResourceSettings, ModifyResourceSettings, RemoveResourceSettings, ExportSystemDefinition, ImportSystemDefinition, ValidatePlannedSystem, RealizePlannedSystem, UpdateVirtualMachine, ConvertVirtualHardDisk, CopyFileToGuest, SetDebugPort, InstantiateVirtualSystem.

Msvm_VirtualSystemManagementServiceSettingData — host defaults: DefaultExternalDataRoot, DefaultVirtualHardDiskPath, MaximumStorageMigrations, AuthorizationManager, NumaSpanningEnabled.

Msvm_VirtualSystemManagementCapabilities, Msvm_VirtualSystemCapabilities.

Msvm_MetricService, Msvm_BaseMetricDefinition, Msvm_BaseMetricValue, Msvm_AggregationMetricDefinition, Msvm_AggregationMetricValue, Msvm_MetricServiceSettingData — resource metering.

Msvm_ConcreteJob — generic async job: PercentComplete, JobStatus, ErrorCode, ErrorSummaryDescription, ErrorDescription.

Msvm_VirtualSystemExportSettingData, Msvm_SystemExportSettingData, Msvm_VirtualSystemUpgradeSettingData.

Msvm_CompatibilityVector — versioning vector for import.

Msvm_BootSourceSettingData, Msvm_BootSourceComponent — Gen2 boot entries.

Msvm_BIOSElement, Msvm_SystemBIOS — Gen1 BIOS.

4.11. Cluster-specific (root\HyperVCluster\v2)

• Msvm_ClusterV2ElementConformsToProfile
• Duplicates of core classes (ComputerSystem / ConcreteJob / VSSettingData) in cluster scope
• Msvm_FailoverIndication (CIM_ProcessIndication) — failover event
• Msvm_CollectionReplicationService / SettingData — group replication
• Msvm_SharedDiskSetReplicationRelationship — shared-VHDX replication
• Msvm_CollectionRecoveryPoint, Msvm_RecoveryPointOfVirtualSystemCollection

5. Client-Side Settings (UI preferences)

Source: Microsoft.Virtualization.Client.Settings.dll.

The only user-scoped settings class is Microsoft.Virtualization.Client.Settings.SettingsConfigurationOptions (extends .NET ApplicationSettingsBase, singleton Instance). Values persist via the standard .NET user-settings mechanism to:

%LOCALAPPDATA%\Microsoft_Corporation\...\user.config

Persisted preferences:

SettingName	Type	Default	Purpose
ShowSettingsSummary	bool	true	Show the summary panel in Hyper-V Manager's Settings dialog
ShowSettingsHighlights	bool	true	Highlight changed settings in the Settings dialog

That's it for persisted client state. Everything else in this assembly (BiosData, FirmwareData, MemoryData, ProcessorData, NetworkAdapterData, HardDriveData, SecurityData, ReplicationPrimaryData, NetworkSwitchData, FibreChannelPortData, MacAddressRangeData, PhysicalGPUData, etc.) are in-memory UI models backed by WMI Msvm_* on the host via IUpdatable.Put() — not persistent client-side preferences.

UI SettingId categories (referenced by UIFactory.LoadImage, map UI pages to WMI classes):

Memory, FloppyDrive, IdeDvdDrive, ScsiDvdDrive, HardDrive, SharedDrive, VhdDefaultPath, PhysicalGPUManagement, IdeController, ScsiController, Synth3dVideoAdapter, VMNameAndNotes, NetworkAdapterEmulated, NetworkAdapterSynthetic, FibreChannelPort, FcWorldWideNameRange, NetworkSwitch, FibreChannelSan, SerialPort, AddHardware, AddNetworkSwitch, NetworkSwitchExtension, AddFibreChannelSan, OnServiceStart, OnServiceStop, NUMASpanning, VirtualMachineMove, StorageMove, VMConnectKeyboardOption, VMConnectReleaseKey, VMConnectUseEnhancedMode, EnhancedModePolicy, EnableConfirmations, VMSnapshotDefaultSetting, VMSecondLevelPagingPath, IntegrationComponents, Processor, ProcessorCompatibility, ProcessorVNuma, Bios, Firmware, FirmwareBootEntryFile, FirmwareBootEntryUnknown, VirtualMachineDefaultPath, MacAddressRange, RecoveryServerConfiguration, ReplicationPrimary, ReplicationRecovery, ReplicationRecoveryConverted, Security, LegacySecurity, KeyStorageDrive.

6. Environment Variables

No Hyper-V-specific HYPERV_* env vars were found. Usage is limited to standard system variables.

6.1. Native (Win32 GetEnvironmentVariableW)

Variable	Consumers	Purpose
ProgramData	vmcompute.dll, containerdevicemanagement.dll, vmuidevices.dll, vmdynmem.dll, vmsynthstor.dll, vmchipset.dll, VmSynthNic.dll, vsconfig.dll (wrapped as Vml::GetEnvironmentVariableW)	Locate %ProgramData%\Microsoft\Windows\Hyper-V for VM configs, saved state, default VHD directory
USERPROFILE	hvc.exe	Default location for per-user .hvc profile/config file

6.2. Managed (Environment.GetEnvironmentVariable)

Variable	Consumers	Purpose
COMPUTERNAME	Microsoft.Virtualization.Client.Management.dll, Microsoft.HyperV.PowerShell.Cmdlets.dll	Identify local host in connection resolution (Server.LocalHost, IsLocalhostName, ServerNames.Resolve); also used in ServerConnectionException messages
appdata	Microsoft.Virtualization.Client.Common.dll (GetStorageDirectory)	Location for Hyper-V Manager user settings (%APPDATA%\Microsoft\Windows\Hyper-V\...)
VM_CONFIGURATION_ID	Microsoft.Virtualization.Client.VMBrowser.dll	When launched from VMConnect / shell integration, overrides target VM instance ID
VM_CONFIGURATION_SERVER	Microsoft.Virtualization.Client.VMBrowser.dll (m_EnvironmentConfigServerName)	Overrides Hyper-V server name to connect to in VM Browser

No getenv() / _wgetenv() calls in Hyper-V code (the fegetenv matches in HyperVSysprepProvider.dll are FP-environment, not env-vars).

7. Configuration Files (INI / JSON / Other)

No INI files and no on-disk JSON config files are consumed by Hyper-V core binaries. Format is mostly XML plus proprietary binary containers.

7.1. INI / Private Profile API

Only hvc.exe (Hyper-V console connection tool) uses GetPrivateProfileStringW / WritePrivateProfileStringW.

• File path: built from %USERPROFILE%\…\<ConfigFileName>
• Purpose: per-user defaults for hvc sessions — serial port pipe names, last-used VM GUIDs

7.2. XML files

File	Consumer	Purpose
ServerManager\ComponentConfiguration\Hyper-V.xml	ConfigureHyperV.exe	Server Manager role-configuration template (features, sub-services, prerequisites); read at role install
<GuestStateDataRoot>\Virtual Machines\<VMID>.xml	vmms.exe	Legacy pre-v8 per-VM configuration (one XML per VM under the VM's data root)
<datapath>\UndoLog Configuration\<id>.xml	vmms.exe	Transactional undo log for VMMS config mutations
<path>\config.xml	vmms.exe	Per-switch / per-feature configuration file
*_ir.xml	vmms.exe	Import-recovery XML written during VM import/export
*.xml (wildcard scan)	vmms.exe	VMMS enumerates all *.xml under directory on startup (legacy VM discovery)

7.3. Binary / native container formats

Extension	Consumer	Purpose
.vmcx	VMImport.exe, vmms.exe	v8+ VM configuration (binary "virtual machine configuration"; replaced .xml)
.vmgs	vmms.exe	Virtual Machine Guest State — encrypted Gen2 firmware/TPM state for shielded VMs; bound to Msvm_VirtualSystemSettingData.GuestStateFile / .SourceGuestStateFile / .GuestStateDataRoot
.vmrs	vmcompute.exe (HCS)	Virtual Machine Runtime State — memory/runtime snapshot; format Bugcheck_<GUID>.vmrs on crash
.vhd / .vhdx / .vhds / .avhdx	vmms.exe, Msvm_VirtualHardDiskSettingData	VHD formats (dynamic, differencing, shared-set)

7.4. JSON / feature-flagged config

• HcsSchema — referenced as a Wil feature flag (Feature_Vmms_HcsSchema) in Microsoft.Virtualization.Client.Wizards.dll with isAlwaysDisabled = true / isAlwaysEnabled = false. It's a feature toggle that enables the HCS JSON schema path in VMMS; there is no literal HcsSchema.json file on disk. When enabled, vmcompute consumes an in-memory JSON document built via the HCS API.
• No references found to virtualization.cfg or Hyper-V.config filenames.
• NetNat.mof, WindowsVirtualizationUninstall.mof, rootporterr.mof are WMI MOFs, not runtime config files.

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