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ERROR_HV_ACKNOWLEDGED
ERROR_HV_ACKNOWLEDGED is HRESULT 0xC0350016 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: a virtual interrupt or synthetic notification whose acknowledgement transition has already completed. Record the first returning operation and host-side event before a management layer retries or translates it.
Locate the failing boundary
The caller attempted an operation that assumes an outstanding interrupt, but the tracked delivery is already acknowledged. Common investigation targets are duplicate completion, stale tokens, and races between reset and acknowledgement.
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: Do not merge this with ERROR_HV_NOT_ACKNOWLEDGED. Here the state advanced too far or was consumed twice; there it had not advanced far enough.
Build an incident record
| Evidence | Why it changes the diagnosis |
|---|---|
| Acknowledgement token | Record the exact interrupt/source identity and any generation or sequence field. |
| First completion | Locate the thread and timestamp that performed the successful acknowledgement. |
| Second transition | Preserve the call stack and object generation that attempted to acknowledge or manipulate it again. |
| Reset boundary | Record VP reset, partition reset, migration, or teardown events that can invalidate old state. |
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
- Make acknowledgement ownership single-writer or atomically claimed.
- Discard tokens from an earlier VP or partition generation after reset.
- Run a race test between completion, cancellation, and teardown.
- Keep duplicate acknowledgement as a negative test rather than suppressing the HRESULT.
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.
Interpret three controls
Across these controls for it, preserve a virtual interrupt or synthetic notification whose acknowledgement transition has already completed 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. |
Keep neighboring states separate
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.
Prove the correction
A complete fix proves one-and-only-one acknowledgement per delivery and shows stale generations are rejected before reaching the hypervisor. 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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