mshv-ioctls: check capability before using extended property - #337
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The VMM capabilities extended property may return UnknownProperty on older MSHV versions that don't recognize the property code, in addition to AccessDenied. Handle both by returning a zeroed capabilities struct so callers can treat the query as unsupported. Signed-off-by: Muminul Islam <muislam@microsoft.com>
Recent hypervisor versions introduced a new class of hypercalls, HvGetPartitionPropertyEx / HvSetPartitionPropertyEx, that expose so-called "extended" partition properties which do not fit the fixed 64-bit layout of the classic HvGetPartitionProperty. One such property is AssignableSyntheticProcessorFeatures, which advertises the set of synthetic processor feature bits the hypervisor is willing to let the VMM configure on a guest partition. Whether the running hypervisor supports these extended properties (and the AssignableSyntheticProcessorFeatures property in particular) is itself surfaced through the VmmCapabilities partition property. Query that capability first and only fetch the extended property and set the matching synthetic feature bit when the hypervisor advertises support for it; otherwise fall back to the classic default mask. Signed-off-by: Muminul Islam <muislam@microsoft.com>
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With new addressable synthetic feature check fails to boot the VM on older MSHV where the property is not available. This PR checks capability before checking such feature.