Msvm_CompatibilityVector class

Article
01/07/2021

References the compatibility info for a virtual machine (VM) (when run on a VM computer system) or a host (when run on a host computer system).

The following syntax is simplified from MOF code and includes all inherited properties.

Syntax

[Dynamic, Provider("VmmsWmiInstanceAndMethodProvider"), AMENDMENT]
class Msvm_CompatibilityVector
{
  uint32 VectorId;
  uint32 CompareOperation;
  uint64 CompatibilityInfo;
};

Members

The Msvm_CompatibilityVector class has these types of members:

Properties

Properties

The Msvm_CompatibilityVector class has these properties.

CompareOperation

Data type: uint32
Access type: Read-only

Identifies the comparison operation that will return true if and only if two vectors are compatible. The VM's data is on the left hand side of the comparison, and the host's data is on the right hand side.

Equal (0)

Superset (1)

Subset (2)

Disjoint (3)

GreaterThan (4)

GreaterThanOrEqual (5)

LessThan (6)

LessThanOrEqual (7)

Multiple (8)

Divisible (9)

CompatibilityInfo

Data type: uint64
Access type: Read-only

The actual compatibility attribute data that is used for comparison.

VectorId

Data type: uint32
Access type: Read-only

Identifies a compatibility vector that represents a specific attribute. This property is used to match corresponding vectors between a host and a VM.

Remarks

The GetSystemCompatibilityVectors method of the Msvm_VirtualSystemMigrationService class returns an array of Msvm_CompatibilityVector instances for the host (if run on the host) or a VM (if run on the VM). Each Msvm_CompatibilityVector entry in the list describes a compatibility attribute vector. For a VM to be compatible with a host, all of its compatibility attributes must be compatible with the host s attributes.

Each Msvm_CompatibilityVector entry has these properties:

VectorId: Uniquely identifies the compatibility vector. This is used to match the vectors to compare between a host and a VM.
CompareOperation: Identifies the comparison operation that determines whether the vectors are compatible.
CompatibilityInfo: Contains the actual compatibility attribute; This is effectively the attribute payload (e.g. processor feature mask, cache line flush size, etc.)

The set of operations defined for CompareOperation just involve basic integer comparison and bitwise logic. This enables the actual contents of CompatibilityInfo to remain opaque. The set of operations include:

CompareOperation	Description	Pseudocode Comparison
VmCcEqual	VmAttr must equal HostAttr	If (VmAttr == HostAttr)
VmCcSuperSet	VmAttr must be a superset of HostAttr	If ((VmAttr & HostAttr) == HostAttr)
VmCcSubSet	VmAttr must be a subset of HostAttr	If ((VmAttr & HostAttr) == VmAttr)
VmCcDisjointSet	VmAttr must be a disjoint set from HostAttr	If ((VmAttr & HostAttr) == 0)
VmCcGreater	VmAttr must be greater than HostAttr	If (VmAttr > HostAttr)
VmCcGreaterEqual	VmAttr must be greater than or equal to HostAttr	If (VmAttr >= HostAttr)
VmCcLess	VmAttr must be less than HostAttr	If (VmAttr < HostAttr)
VmCcLessEqual	VmAttr must be less than or equal to HostAttr	If (VmAttr <= HostAttr)
VmCcMultiple	VmAttr must be a multiple of HostAttr	If ((VmAttr % HostAttr) == 0)
VmCcDivisor	VmAttr must be a divisor of HostAttr	If ((HostAttr % VmAttr) == 0)

SCVMM needs to do these steps to determine whether a VM is compatible with a host.

To determine whether a VM is compatible with a host

Iterate through all of the Msvm_CompatibilityVector elements for the VM.
For each Msvm_CompatibilityVector element, use the compatibility operation specified in CompareOperation to compare the VM s hardware compatibility vector with the corresponding compatibility vector for the host.
If the all of the Msvm_CompatibilityVector elements from the VM are deemed compatible, the VM is compatible with the host (from a processor feature perspective).

Requirements

Requirement	Value
Minimum supported client	Windows 8.1 [desktop apps only]
Minimum supported server	Windows Server 2012 R2 [desktop apps only]
Namespace	Root\Virtualization\V2
MOF	WindowsVirtualization.V2.mof
DLL	Vmms.exe