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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. It applies to the state machine for a previously delivered virtual interrupt or synthetic notification.
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 evidence.
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. |
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
| Control | Interpretation | Hold constant |
|---|---|---|
| Single producer and consumer | If it disappears with serialized ownership, the queue, handler, acknowledgement, or delivery race is implicated. | Preserve message type, partition, target VP, and queue capacity. |
| Fresh channel generation | 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 test. |
| Controlled stall or burst | 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
Keep the hexadecimal result 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.
Technical references
- Microsoft Open Specifications: HRESULT values — used to interpret this result.
- Microsoft TLFS: inter-partition communication — used to interpret this result.
- Microsoft TLFS: HV_MESSAGE — used to interpret this result.
- Microsoft: Hyper-V architecture — used to interpret this result.
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