Control status register access to enable domain reconfiguration

• US 20040221036A1
• Filed: 05/01/2003
• Published: 11/04/2004
• Est. Priority Date: 05/01/2003
• Status: Active Grant

• Current Assignee: Oracle America, Inc. (Oracle Corporation)
• Original Assignee: Sun Microsystems Incorporated (Oracle Corporation)
• Inventors: Smith, Brian L.
• Granted Patent: US 7,409,722 B2
• Time in Patent Office: Days
• US Class Current: 709/225
• CPC Class Codes: G06F 9/468 Specific access rights for resources, e.g. using capability register

Abstract

A method and mechanism for enabling access to a protected register in a client. A system including multiple clients, such as components and devices, is coupled to a service processor which is configured to manage the system. Clients which are managed by the service processor include control and status registers which are protected from access by unauthorized entities. Access rights for particular registers may be restricted to only the service processor. Clients include a timer which the service processor periodically updates. In the event communication is lost between the service processor and a client, the timer is not updated. In response to detecting the timer was not updated, the client is configured to alter the access rights of the register in order to permit an alternate entity to access the protected register. The service processor may then utilize the alternate entity as a proxy in order to transfer the client state to another client and configure the affected client out of the system.

Claims

1. A method for use in a system including registers with limited access rights, said method comprising:

configuring access rights to a client register, wherein said access rights indicate the register is only accessible by one or more authorized entities including a first master;

conveying an indication from said first master to said client, wherein a timer of said client is configured to be updated in response to said indication;

detecting in said client a first condition, said first condition comprising said timer has not been updated within a first period of time; and

altering said access rights to permit access by a previously unauthorized second master, wherein said altering is in response to said detecting.

2. The method as recited in claim 1, further comprising:

said second master attempting to access said client register; and

said client allowing said second master to access said register in response to detecting said access rights indicate said second master is permitted to access said register.

3. The method as recited in claim 2, wherein allowing said second master to access said register is in further response to detecting said first condition.

4. The method as recited in claim 2, further comprising:

conveying an error indication from said client to said first master in response to said detecting; and

said first master utilizing said second master as a proxy to access said client register in response to detecting said error indication.

5. The method as recited in claim 4, further comprising reconfiguring said system to exclude said client.

6. The method as recited in claim 5, wherein said reconfiguring includes transferring state from said client to an alternate client.

7. The method as recited in claim 1, wherein said first master comprises a service processor.

8. A system comprising:

a first master; and

a plurality of clients coupled to said first master, wherein each of said clients include a timer configured to be updated responsive to an indication received from the first master;

wherein a first client of said clients includes a register with access rights indicating access is only permitted by one or more authorized entities including the first master, and wherein in response to detecting a timer of said first client has not been updated within a first period of time, said first client is configured to alter said access rights to permit access by a previously unauthorized second master.

9. The system as recited in claim 8, wherein said first master comprises a service processor, said second master is configured to attempt to access said client register responsive to an indication received from the service processor, and said client is configured to allow said second master to access said register in response to detecting said access rights indicate said second master is permitted to access said register.

10. The system as recited in claim 9, wherein said client is configured to allow said second master to access said register in further response to detecting said timer has not been updated within a first period of time.

11. The system as recited in claim 9, wherein the client is further configured to convey an error indication from said client to said first master in response to said detecting, and said first master is configured to utilize said second master as a proxy to access said client register in response to detecting said error indication.

12. The system as recited in claim 11, wherein the first master is configured to use said proxy to reconfigure the client out of the system.

13. The system as recited in claim 12, wherein said first master is further configured to use said proxy to transfer state from the client to an alternate client prior to reconfiguring the client out of the system.

14. The system as recited in claim 8, wherein said first master is coupled to each of said clients via a service processor bus.

15. The system as recited in claim 14, wherein each of said clients are coupled to an operations bus.

20. The client as recited in claim 12, wherein the control unit is configured to distinguish the first master from the second master via a bus master ID received with an attempted access to the register.

16. A client comprising:

one or more components accessible by an external first master; and

a control unit including a register configured for access by only one or more authorized entities including the first master;

wherein the client includes a timer corresponding to the register, wherein the timer is configured to be updated in response to an indication received from the service processor, and wherein in response to detecting the timer has not been updated within a first period of time, said control unit is configured to alter the access rights of the register to permit access by a previously unauthorized second master.

17. The client as recited in claim 16, wherein the control unit is configured to allow the second master to access the register in response to detecting the access rights indicate the second master is permitted to access said register.

18. The client as recited in claim 17, wherein the control unit is configured to allow the second master to access the register in further response to detecting that the timer has not been updated within a first period of time.

19. The client as recited in claim 16, wherein the control unit is further configured to convey an error indication to the first master in response to said detecting.

21. A method for use in a system including registers with limited access rights, said method comprising:

receiving a command to update a timer within a first client, said command being configured to prevent said timer from expiring;

detecting a first command from a first master, said first command being configured to access a register corresponding to said client, wherein access rights corresponding to said register indicate the register is only accessible by said first command if said timer has expired; and

denying access to said register by said first command in response to detecting said timer has not expired.

22. The method of claim 21, further comprising conveying an error signal indicating an unauthorized access by said first master has been attempted.

23. A system comprising:

a first master; and

a client coupled to said first master, wherein said client includes;

a timer configured to be updated responsive to an indication received from the first master; and

a register with access rights indicating access is only permitted by one or more authorized entities including the first master;

wherein in response to detecting a first command from a second master, said first command being configured to access said register, said client is configured to;

deny access to said register by said first command in response to detecting said timer has not expired.

24. The system of claim 23, wherein said client is further configured to convey an error signal to said first master indicating an unauthorized access by said second master has been attempted.

25. A client comprising:

a timer configured to be updated responsive to an indication received from the first master; and

a register with access rights indicating access is only permitted by one or more authorized entities including the first master;

wherein in response to detecting a first command from a second master, said first command being configured to access said register, said client is configured to;

deny access to said register by said first command in response to detecting said timer has not expired.

26. The client of claim 25, wherein said client is further configured to convey an error signal to said first master indicating an unauthorized access by said second master has been attempted.