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WHV_E_INSUFFICIENT_BUFFER
WHV_E_INSUFFICIENT_BUFFER is HRESULT 0x80370301 in the Windows Hypervisor Platform query contract area of the Windows virtualization stack. The built-in message names the immediate result; the useful custom context is the exact boundary: a caller-provided output buffer used by a Windows Hypervisor Platform property, capability, register, or state query. Record the first returning operation and host-side event before a management layer retries or translates it.
Locate the failing boundary
The API could identify the requested data, but the byte capacity supplied by the caller cannot hold the complete result. This is normally a sizing contract at the WHP boundary rather than hypervisor-pool exhaustion.
This result is on the public Windows Hypervisor Platform surface. A WHP partition is created, configured through properties, and then set up before virtual processors and GPA mappings are used. Keep the exact WHv* function, selector, structure size, and Windows build with it, because that API contract is more precise than the final application message.
Neighboring result: Keep it separate from ERROR_HV_INSUFFICIENT_BUFFER and ERROR_HV_INSUFFICIENT_BUFFERS: those are hypervisor-facility results, while this result belongs to the user-mode Windows Hypervisor Platform HRESULT surface.
Build an incident record
| Evidence | Why it changes the diagnosis |
|---|---|
| Returning WHv* function | Record the exact function and query/property selector; different structures have different version and size rules. |
| Input and returned sizes | Preserve allocated bytes, structure Size fields, element counts, and any required-size value returned by the API. |
| Header/runtime version | Record the SDK definitions used to compile and the Windows build that supplied WinHvPlatform.dll. |
| Retry behavior | Show whether a correctly resized, zero-initialized buffer succeeds without changing the partition. |
Preserve identifiers and counts without dumping guest secrets or unrelated memory. Useful this result timestamps include the last successful operation, first failure, any automatic retry, and the object-generation change that followed.
Run narrow checks
- Validate every count-to-byte conversion for overflow before allocation.
- Use the API-defined size or count returned by the first call when a two-call pattern is supported.
- Zero reserved fields and pass the structure version expected by the target Windows build.
- Retry only after resizing; recreating the partition does not repair a caller buffer contract.
Run this result checks in a minimal WHP harness before changing the VM. Keep the exact function, enum selector, byte count, structure layout, architecture, and Windows build; recreate the partition only when the tested contract requires a new generation.
Interpret three controls
Across these controls for it, preserve a caller-provided output buffer used by a Windows Hypervisor Platform property, capability, register, or state query as the boundary under test.
| Control | Interpretation | Hold constant |
|---|---|---|
| Direct call versus wrapper — it | Call the same WHP function from a minimal native harness. If it disappears, inspect binding, enum, packing, or size conversion in the wrapper. | Keep the Windows build, selector, property data, and partition state fixed for it. |
| Known older selector — it | Use a documented older capability or property through the same path. A success narrows it to selector/version negotiation rather than general WHP availability. | Change only the selector and matching value structure. |
| Second supported Windows build — it | If it follows one runtime build, compare capability discovery and API availability before changing VM configuration. | Use the same executable, architecture, and request bytes in the result comparison. |
Keep neighboring states separate
Do not reboot Windows or recreate the VM as the first response to it. In the case, a reboot can erase caller selector, structure, size, and runtime-capability evidence while leaving the programming error unchanged.
Prove the correction
A correct fix makes the same query return S_OK with all requested fields present and no truncation, on both the original and a boundary-size test. Repeat the original operation under the original supported conditions and retain one deliberate negative control. A management command succeeding on a different object is not sufficient to close this incident.
Technical references
These sources define the HRESULT and the public WHP contract used for it; the exact called function and property/size rules remain decisive.
- Microsoft Win32 metadata: winerror.h — used to interpret the boundary.
- Microsoft: Windows Hypervisor Platform API — used to interpret the boundary.
- Microsoft: WHvCreatePartition — used to interpret the boundary.
- Microsoft: WHvSetupPartition — used to interpret the boundary.
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