Agilex™ 5 ES Device Errata and User Guidelines

ID 825514
Date 12/09/2024
Public
Document Table of Contents

3.5.5. 2675030: Multiple Events reported to Event queue for a single transaction

Description

To avoid a synchronization deadlock, when a synchronization occurs, invalidated translations in the TBU might discard their translation and fetch a translation again.

Affected versions treat translation faults as invalidated. As a result, a transaction that faults in the TCU reports an event, and returns a fault response to the TBU might have its fault response discarded by the TBU and a new translation fetched from the TCU.

This new translation request can:

  • Fault in the same manner, causing a repeated event to be reported
  • Fault in a different manner, causing two different events to be reported for the same transaction
  • Succeed, causing an event to be recorded for a transaction that has translated successfully

It is possible, but unlikely, that this sequence can occur multiple times.

Conditions

The issue can occur when:

  • The event queue is enabled
  • A transaction encounters a fault during translation that results in an event being reported
  • That transaction has an ordering requirement in the TBU to be issued behind, or responded after, a second transaction
  • A synchronization request arrives at the TBU from the TCU

Impact

The software that reads the content of the event queue might encounter events that relate to a transaction for which it has already read an event from the queue. The result of this depends on the behavior of the software.

Workaround

No workaround is required

Category

Category C