System for synchronizing logical clock in logical partition of host processor with external time source by combining clock adjustment value with specific value of partition

An apparatus for synchronizing logical and physical clocks in a logically partitioned data processing system having at least one logical partition, and having a hypervisor, said apparatus comprising:

• a) a host processor, having a host clock;
• b) a logical clock in said at least one logical partition, said logical clock having a value created by arithmetically combining said host clock with a value specific to said logical partition;
• c) an external time source connected to said host processor;
• d) means for detecting a need for synchronization condition between the external time source and said host clock;
• e) means for insulating said at least one logical partition from host clock synchronization during host clock synchronization after said detecting of said need for synchronization;
• f) means for synchronizing said host clock with said external time source;
• g) means for modifying said logical clock, by calculating a clock adjustment value and applying said clock adjustment value to said value specific to said logical partition by arithmetically combining said clock adjustment value with said value specific to said logical partition, so that logical clock consistency is maintained despite said host clock synchronization;
• and
• h) synchronizing the logical clock with the external time source after said host clock has been synchronized with said external time source if the logical partition is executing in a mode having access to the external time source.

A method for synchronizing a logical clock in a logical partition executing on a host processor having a host clock, and controlled by a hypervisor, with an external time source connected to the host processor, said logical clock having a value created by arithmetically combining said host clock with a value specific to said logical partition, said method comprising the steps, performed by said hypervisor, of:

• a) detecting a synchronization check indicating an out-of-synchronization condition between the external time source and the host clock;
• b) insulating the logical partition from host clock synchronization after said detecting of said synchronization check, said step of insulating further comprising the steps of:
• i) preventing a user dispatch within the logical partition during said host clock synchronization;
• ii) setting a control to intercept a timer facility instruction;
• iii) setting a creep mode indicator for said host clock, said creep mode indicator causing a simulation of any store clock instruction during said host clock synchronization by incrementing, by a small positive value, a last host clock value on each said store clock instruction;
• and
• iv) setting a dummy value of a clock comparator, said dummy value being chosen to prevent a clock comparator interruption from occurring during said host clock synchronization;
• c) synchronizing the host clock with the external time source;
• d) calculating a clock adjustment value for use by said hypervisor in maintaining clock consistency;
• e) applying said clock adjustment value to said value specific to said logical partition by arithmetically combining said clock adjustment value with said value specific to said logical partition;
• and
• f) setting a notification to synchronize the logical clock with the host clock and the external time source, after said synchronizing of the host clock with the external time source, if the logical partition is executing in a mode having access to the external time source.

An apparatus for synchronizing logical and physical clocks in a logically partitioned data processing system having at least one logical partition and having a hypervisor, said apparatus comprising:

• a) a host processor having a host clock;
• b) a logical clock in said at least one logical partition, said logical clock having a value created by arithmetically combining said host clock with a value specific to said logical partition;
• c) an external time source connected to said host processor;
• d) means for detecting a synchronization check between the external time source and said host clock;
• e) means for insulating said at least one logical partition from host clock synchronization during host clock synchronization after said detecting of said synchronization check, said means for insulating further comprising:
• i) means for preventing a user dispatch within said at least one logical partition during said host clock synchronization;
• ii) means for intercepting and simulating execution of a timer instruction, said simulation providing function equivalence to said timer instruction, said means for intercepting and simulating execution comprising a creep mode indicator means for adjusting a host clock value associated with said host clock, said creep mode indicator means, when set, causing a simulation of any store clock instruction during said host clock synchronization by incrementing, by a small positive value, a last host clock value on each said store clock instruction;
• and
• iii) a dummy clock comparator, said dummy clock comparator being chosen to prevent a clock comparator interruption from occurring during said host clock synchronization;
• f) means for synchronizing said host clock with said external time source;
• and
• g) means for modifying said logical clock by calculating a clock adjustment value and applying said clock adjustment value to said value specific to said logical partition by arithmetically combining said clock adjustment value with said value specific to said logical partition so that logical clock consistency is maintained despite said host clock synchronization.

A method for synchronizing a logical clock in a logical partition executing on a host processor having a host clock with an external time source connected to the host processor, said logical clock having e value created by arithmetically combining a host clock value with a value specific to said logical partition, said method comprising the steps of:

• synchronizing said host clock with said external time source, said host clock having an initial value before synchronization with said external time source and a final value after synchronization with said external time source;
• calculating a clock adjustment value as a function of the difference between said initial and final host clock values;
• and
• applying said clock adjustment value to said logical partition by arithmetically combining said clock adjustment value with said value specific to said logical partition;
• and
• synchronizing said logical clock with said external time source after said host clock has been synchronized with said external time source if said logical partition is executing in a mode having access to said external tame source.

Apparatus for synchronizing a logical clock in a logical partition executing on e host processor having a host clock with an external time source connected to the host processor, said logical clock having a value created by arithmetically combining a host clock value with a value specific to said logical partition, said apparatus comprising:

• means for synchronizing said host clock with said external time source, said host clock having an initial value before synchronization with said external time source and a final value after synchronization with said external time source;
• means for calculating a clock adjustment value as a function of the difference between said initial and final host clock values;
• and
• means for applying said clock adjustment value to said logical partition by arithmetically combining said clock adjustment value with said value specific to said logical partition;
• and
• means for synchronizing said logical clock with said external time source after said host clock has been synchronized with said external time source if said logical partition is executing in a mode having access to said external time source.