Memory management

A host data processing system configured to provide a virtual operating environment for one or more guest data processing systems, the host data processing system comprising:

• a memory management unit configured to initiate a transaction for translation of a guest system memory address to a host system physical address in response to a transaction request from a device overseen by a guest system for access to system memory according to that guest system memory address;
• a transaction buffer configured to store identification information relating to each transaction including at least data identifying the device which requested the transaction;
• error handling logic configured, for a stalled transaction, being a transaction incurring an error condition which is potentially resolvable by the guest system overseeing the device which requested the transaction, to:
• (i) store identification information relating to that transaction including at least data identifying the device which requested the transaction;
• (ii) provide information indicative of the translation error condition to the guest system overseeing the device which requested the transaction;
• and
• (iii) defer continued handling of the stalled transaction until a subsequent command is received from that guest system relating to the stalled transaction;
• a detector configured to detect initiation of a closure process relating to a guest system;
• and
• cancellation logic, responsive to initiation of the closure process, configured to initiate cancellation of any currently stalled transactions for devices overseen by that guest system for which a command has not yet been received from that guest system.

A host data processing system operable to provide a virtual operating environment for one or more guest data processing systems, the host data processing system comprising:

• means for initiating a transaction for translation of a guest system memory address to a host system physical address in response to a transaction request from a device overseen by a guest system for access to system memory according to that guest system memory address;
• means for storing identification information relating to each transaction including at least data identifying the device which requested the transaction;
• means operable in respect of a stalled transaction, being a transaction incurring an error condition which is potentially resolvable by the guest system overseeing the device which requested the transaction, for:
• (i) storing identification information relating to that transaction including at least data identifying the device which requested the transaction;
• (ii) providing information indicative of the translation error condition to the guest system overseeing the device which requested the transaction;
• and
• (iii) deferring continued handling of the stalled transaction until a subsequent command is received from that guest system relating to the stalled transaction;
• means for detecting initiation of a closure process relating to a guest system;
• and
• means, responsive to initiation of the closure process, for initiating cancellation of any currently stalled transactions for devices overseen by that guest system for which a command has not yet been received from that guest system.