On Mon, Feb 02, 2026 at 07:26:06PM +0000, Stanislav Kinsburskii wrote: > Query the hypervisor for integrated scheduler support and use it if > configured. > > Microsoft Hypervisor originally provided two schedulers: root and core. The
Microsoft Hypervisor provides three schedulers: root, classic (with or without SMT) and core. The latter two are hypervisor based. > root scheduler allows the root partition to schedule guest vCPUs across > physical cores, supporting both time slicing and CPU affinity (e.g., via > cgroups). In contrast, the core scheduler delegates vCPU-to-physical-core > scheduling entirely to the hypervisor. > > Direct virtualization introduces a new privileged guest partition type - L1 Level-1 Virtualization Host. > Virtual Host (L1VH) — which can create child partitions from its own > resources. These child partitions are effectively siblings, scheduled by > the hypervisor's core scheduler. This prevents the L1VH parent from setting > affinity or time slicing for its own processes or guest VPs. While cgroups, > CFS, and cpuset controllers can still be used, their effectiveness is > unpredictable, as the core scheduler swaps vCPUs according to its own logic > (typically round-robin across all allocated physical CPUs). As a result, > the system may appear to "steal" time from the L1VH and its children. > > To address this, Microsoft Hypervisor introduces the integrated scheduler. > This allows an L1VH partition to schedule its own vCPUs and those of its > guests across its "physical" cores, effectively emulating root scheduler > behavior within the L1VH, while retaining core scheduler behavior for the > rest of the system. > > The integrated scheduler is controlled by the root partition and gated by > the vmm_enable_integrated_scheduler capability bit. If set, the hypervisor > supports the integrated scheduler. The L1VH partition must then check if it > is enabled by querying the corresponding extended partition property. If > this property is true, the L1VH partition must use the root scheduler > logic; otherwise, it must use the core scheduler. This requirement makes > reading VMM capabilities in L1VH partition a requirement too. > > Signed-off-by: Andreea Pintilie <[email protected]> > Signed-off-by: Stanislav Kinsburskii <[email protected]> > --- [...] > +++ b/include/hyperv/hvhdk_mini.h > @@ -87,6 +87,9 @@ enum hv_partition_property_code { > HV_PARTITION_PROPERTY_PRIVILEGE_FLAGS = 0x00010000, > HV_PARTITION_PROPERTY_SYNTHETIC_PROC_FEATURES = 0x00010001, > > + /* Integrated scheduling properties */ > + HV_PARTITION_PROPERTY_INTEGRATED_SCHEDULER_ENABLED = 0x00020005, The internal name is "HvPartitionPropertyHierarchicalIntegratedSchedulerEnabled". You missed the "Hierarchical" part in the property code name. Wei > + > /* Resource properties */ > HV_PARTITION_PROPERTY_GPA_PAGE_ACCESS_TRACKING = 0x00050005, > HV_PARTITION_PROPERTY_UNIMPLEMENTED_MSR_ACTION = 0x00050017, > @@ -102,7 +105,7 @@ enum hv_partition_property_code { > }; > > #define HV_PARTITION_VMM_CAPABILITIES_BANK_COUNT 1 > -#define HV_PARTITION_VMM_CAPABILITIES_RESERVED_BITFIELD_COUNT 59 > +#define HV_PARTITION_VMM_CAPABILITIES_RESERVED_BITFIELD_COUNT 57 > > struct hv_partition_property_vmm_capabilities { > u16 bank_count; > @@ -119,6 +122,8 @@ struct hv_partition_property_vmm_capabilities { > u64 reservedbit3: 1; > #endif > u64 assignable_synthetic_proc_features: 1; > + u64 reservedbit5: 1; > + u64 vmm_enable_integrated_scheduler : 1; > u64 reserved0: > HV_PARTITION_VMM_CAPABILITIES_RESERVED_BITFIELD_COUNT; > } __packed; > }; > > >
