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ERROR_HV_NOT_ACKNOWLEDGED
ERROR_HV_NOT_ACKNOWLEDGED is HRESULT 0xC0350014 in the virtual interrupt acknowledgement state area of the Windows virtualization stack. The built-in message names the immediate result; the useful custom context is the exact boundary: the state machine for a previously delivered virtual interrupt or synthetic notification. Record the first returning operation and host-side event before a management layer retries or translates it.
What the code establishes
The next transition was attempted while the prior interrupt remained outstanding. The useful evidence is the delivery sequence, target VP, interrupt identity, and acknowledgement boundary—not general VM network health.
This result belongs to the hypervisor facility rather than the higher-level VM management UI. The TLFS and WHP documentation provide the surrounding partition, message, memory, and virtual-processor model, but the first low-level operation and any nested status remain the authoritative incident boundary.
Neighboring result: ERROR_HV_ACKNOWLEDGED is the opposite ordering fault: there the prior interrupt is already acknowledged. Both indicate state-machine misuse, but at different edges.
Evidence that should survive remediation
| Evidence | Why it changes the diagnosis |
|---|---|
| Interrupt identity | Record vector, synthetic source, target partition and virtual processor. |
| Sequence numbers | Keep delivery, observation, service, end-of-interrupt, and acknowledgement timestamps. |
| VP execution state | Capture whether the target VP was running, suspended, intercepted, or being reset. |
| Concurrent producers | Identify threads or components capable of delivering or acknowledging the same source. |
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.
Controlled diagnostic sequence
- Serialize transitions for one interrupt source and target VP.
- Confirm acknowledgement is issued only after the guest or virtualization stack consumes the prior delivery.
- Instrument duplicate delivery and lost-ack paths separately.
- Reset the test state explicitly between runs; do not rely on a VM restart to hide ordering defects.
Exercise this result with bounded producers and a fully instrumented consumer. Preserve message ordering, queue generation, handler ownership, target VP, and acknowledgement timestamps while changing only one concurrency condition.
Read the comparison tests
Across these controls for it, preserve the state machine for a previously delivered virtual interrupt or synthetic notification as the boundary under test.
| Control | Interpretation | Hold constant |
|---|---|---|
| Single producer and consumer — this result | If it disappears with serialized ownership, the queue, handler, acknowledgement, or delivery race is implicated. | Preserve message type, partition, target VP, and queue capacity for it. |
| Fresh channel generation — it | A new queue or handler generation changing it points to stale registration, backlog, or incomplete teardown. | Keep payload, producer order, and host build unchanged in the result test. |
| Controlled stall or burst — it | Deliberately slow the consumer or bound the producer rate. The threshold at which it appears identifies backpressure versus lifecycle failure. | Record queue depth, oldest-item age, and acknowledgement timing. |
Avoid the wrong recovery
A VM or service restart can empty queues and replace handler generations, temporarily hiding it. Before clearing the result channel, capture depth, oldest item, owner, delivery sequence, and acknowledgement state.
Keep the hexadecimal it value and any nested hypervisor status. Higher layers can map distinct resource, buffer, message, or state failures to the same generic start or migration message.
Acceptance test
The sequence is corrected when every delivery has exactly one later acknowledgement and stress testing produces neither NOT_ACKNOWLEDGED nor ACKNOWLEDGED. 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 it and the public Hyper-V architecture surrounding the internal state. They do not create a public user-mode VID API for the named object.
- Microsoft Open Specifications: HRESULT values — used to interpret the boundary.
- Microsoft TLFS: inter-partition communication — used to interpret the boundary.
- Microsoft TLFS: HV_MESSAGE — used to interpret the boundary.
- Microsoft: Hyper-V architecture — used to interpret the boundary.
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