Architecture and method for sharing TLB entries through process IDS

• US 5,754,818 A
• Filed: 03/22/1996
• Issued: 05/19/1998
• Est. Priority Date: 03/22/1996
• Status: Expired due to Term

• Current Assignee: Oracle America, Inc. (Oracle Corporation)
• Original Assignee: Sun Microsystems Incorporated (Oracle Corporation)
• Inventors: Mohamed, Ahmed Hassan
• Primary Examiner(s): Hafiz, Tariq R.
• Assistant Examiner(s): Verbrugge, Kevin
• Application Number:
  US08/620,464
• Time in Patent Office: 788 Days
• Field of Search: 395/415, 395/416, 395/417, 395/471, 395/483, 395/677, 395/678, 395/418, 395/419, 395/420
• US Class Current: 711/207
• CPC Class Codes: G06F 12/1036 for multiple virtual address spaces, e.g. segmentation G06F12/1045 takes precedence

Abstract

An address translation control circuit which operates in connection with a processor and a translation look-aside buffer ("TLB") to perform virtual-to-physical address translations through shared entries of the TLB. The address translation control circuit comprises a primary context storage element, a group context storage element, a context matching circuit, a comparing unit and a logic unit. The context matching circuit is coupled to primary and group context storage elements to receive their context numbers and reads a context identification number and a context select bit value from a chosen translation entry of the TLB. Concurrently, the comparing unit compares the virtual address contained in that entry with the virtual address requested for translation by the processor. The logic unit receives the outputs from the context matching circuit and the comparing unit and signals operating system software whether an appropriate translation has been found in the TLB.

Claims

1. An address translation control circuit configured to operate in connection with a processor and a translation look-aside buffer that includes a translation table having at least one translation table entry including a pre-stored virtual address and a context identification number and also configured to translate a requested virtual address from the processor into a physical address, the address translation control circuit comprising:

a plurality of context storage elements, wherein a first context number is contained in a first context storage element and a second context number is contained in a second context storage element; and

circuitry coupled to said plurality of context storage elements, said circuitry being configured to output a translation Hit signal to indicate that the translation look-aside buffer is currently storing the physical address when said context identification number is equivalent to a selected context number being one of said first and second context numbers and the pre-stored virtual address is equivalent to the requested virtual address.

2. The address translation control circuit according to claim 1, wherein said circuitry of the address translation control circuit includes

a context matching circuit configured to (i) receive said first and second context numbers and said context identification number and (ii) output at least one context matching signal indicating whether said context identification number is equivalent to a selected context number being one of said first and second context numbers;

a comparing unit configured to (i) compare the requested virtual address with the pre-stored virtual address and (ii) output a comparison signal indicating whether the pre-stored virtual address is equivalent to the requested virtual address; and

a logic unit coupled to said context matching circuit and said comparing unit, said logic unit is configured to output said translation Hit signal if said context matching signal indicates that said context identification number is equivalent to said selected context number and said comparison signal indicates that the pre-stored virtual address is equivalent to the requested virtual address.

3. The address translation control circuit according to claim 2, wherein said context matching circuit of said circuitry includes

a multiplexing unit configured to receive as inputs said first context number, said second context number and a context select bit from the at least one translation table entry;

and

a second comparing unit configured to receive and compare an output of said multiplexing unit with the context identification number from the at least one translation table entry.

4. The address translation control circuit according to claim 2, wherein said context matching circuit of said circuitry includes

a first comparing unit configured to (i) receive and compare said first context number with said context identification number and (ii) output a first comparing signal indicating whether said first context number is equivalent to said context identification number;

a first matching logic gate configured to (i) receive as inputs said first comparing signal and a context select bit and (ii) output a first context matching signal to said logic unit; and

a second comparing unit configured to (i) receive and compare said second context number with said context identification number and (ii) output a second comparing signal indicating whether said second context number is equivalent to said context identification number;

an inverter configured to receive and complement said context select bit; and

a second matching logic gate configured to (i) receive as inputs said second comparing signal and said complement of said context select bit and (ii) output a second context matching signal to said logic unit.

5. The address translation control circuit according to claim 4, wherein said logic unit of said circuitry includes

a first logic gate configured to (i) receive as inputs said first and second context matching signals and (ii) produce a first logic output signal if one of said first and second context matching signals is active;

and

a second logic gate configured to (i) receive as inputs said first logic output signal and said comparison signal and (ii) output said translation Hit signal if said first logic output signal is indicating that said context identification number is equivalent to one of said first and second context numbers and said comparison signal is indicating that the pre-stored virtual address is equivalent to the requested virtual address.

6. The address translation control circuit according to claim 4, wherein said logic unit of said circuitry includes

a first logic gate configured to (i) receive as inputs said first and second context matching signals and a global bit from the at least one translation table entry and (ii) produce a first logic output signal indicating that one of a plurality of conditions exists, whereas said plurality of conditions include said context identification number being equivalent to said selected context number and a translation associated with the requested virtual address is context independent;

and

a second logic gate configured to (i) receive as inputs said first logic output signal and said comparison signal and (ii) output said translation Hit signal if said first logic output signal is indicating that one of said plurality of conditions exists and said comparison signal is indicating that the pre-stored virtual address is equivalent to the requested virtual address.

7. An address translation control circuit configured to operate in connection with a processor and a translation look-aside buffer that includes a translation table having at least one translation table entry including a pre-stored virtual address and a context identification number and also configured to translate a requested virtual address from the processor into a physical address, the address translation control circuit comprising:

a primary context storage element configured to store a first context number;

a group context storage element configured to store a second context number;

a context matching circuit configured to receive said first context number from said primary context storage element, said second context number from said group context storage element and said context identification number from the at least one translation table entry and to output at least one context matching signal indicating whether said context identification number is equivalent to a selected context number being one of said first and second context numbers;

a comparing unit configured to compare the pre-stored virtual address with the requested virtual address and to output a comparison signal indicating whether the pre-stored virtual address is equivalent to the requested virtual address; and

a logic unit coupled to said context matching circuit and said comparing unit, said logic unit being configured to output a translation Hit signal if said context matching signal indicates that said context identification number is equivalent to said selected context number and said comparison signal indicates that the pre-stored virtual address is equivalent to the requested virtual address.

8. A computer system comprising:

a bus; and

a processing unit coupled to said bus, said processing unit including

a processor configured to issue a request to translate a requested virtual address into a physical address, and

a memory management unit coupled to said processor, said memory management unit including

a translation look-aside buffer including a translation table, said translation table having at least one translation table entry including a pre-stored virtual address and a context identification number, and

an address translation control circuit configured to (i) receive a first context number, a second context number and said context identification number and (ii) output a translation Hit signal to indicate that the translation look-aside buffer is currently storing the physical address when said context identification number is equivalent to a selected context number being one of said first and second context numbers and the pre-stored virtual address is equivalent to the requested virtual address.

9. The computer system according to claim 8, wherein said address translation control circuit of said memory management unit includes

a plurality of context storage elements, wherein said first context number is contained in a first context storage element and said second context number is contained in a second context storage element;

and

circuitry coupled to said plurality of context storage elements, said circuitry being configured to output said translation Hit signal.

10. The computer system according to claim 9, wherein said circuitry of said address translation control circuit includes

a context matching circuit configured to receive said first and second context numbers and said context identification number and to output at least one context matching signal indicating whether said context identification number is equivalent to a selected context number being one of said first and second context numbers;

a comparing unit configured to compare the pre-stored virtual address with the requested virtual address and to output a comparison signal indicating whether the pre-stored virtual address is equivalent to the requested virtual address; and

a logic unit coupled to said context matching circuit and said comparing unit, said logic unit is configured to output a translation Hit signal if said context matching signal indicates that said context identification number is equivalent to said selected context number and said comparison signal indicates that the pre-stored virtual address is equivalent to the requested virtual address.

11. The computer system according to claim 10, wherein said at least one context matching signal from said context matching circuit is active if said selected context number is equivalent to said context identification number.

12. The computer system according to claim 11, wherein said comparison signal from said comparing unit is active if said requested virtual address from the processor is equivalent to said pre-stored virtual address.

13. The computer system according to claim 12, wherein said logic unit of said address translation control circuit includes

a first logic gate configured to (i) receive as inputs said first and second context matching signals and (ii) produce a first logic output signal to indicate that one of said first and second context matching signals is active;

and

a second logic gate configured to (i) receive as inputs said first logic output signal and said comparison signal and (ii) output said translation Hit signal if said first logic output signal indicates that said context identification number is equivalent to one of said first and second context numbers and said comparison signal indicates that the pre-stored virtual address is equivalent to the requested virtual address.

14. The computer system according to claim 10, wherein said logic unit of said address translation control circuit includes

a first logic gate configured to (i) receive as inputs said first and second context matching signals and a global bit from the at least one translation table entry and (ii) produce a first logic output signal indicating that one of a plurality of conditions exists, whereas said plurality of conditions include said context identification number being equivalent to said selected context number and a translation associated with the requested virtual address is context independent;

and

a second logic gate configured to (i) receive as inputs said first logic output signal and said comparison signal and (ii) output said translation Hit signal whether said first logic output signal indicates that one of said plurality of conditions exists and said comparison signal indicates that the pre-stored virtual address is equivalent to the requested virtual address.

15. The computer system according to claim 10, wherein said context matching circuit of said address translation control circuit includes

a multiplexing unit configured to receive as inputs said first context number, said second context number and a context select bit from the at least one translation table entry;

and

a second comparing unit configured to receive and compare an output of said multiplexing unit with the context identification number from the at least one translation table entry.

16. The computer system according to claim 10, wherein said context matching circuit of said address translation control circuitry includes

a first comparing unit configured to (i) receive and compare said first context number with said context identification number and (ii) output a first comparing signal indicating whether said first context number is equivalent to said context identification number;

a first matching logic gate configured to (i) receive as inputs said first comparing signal and a context select bit and (ii) output a first context matching signal to said logic unit; and

a second comparing unit configured to (i) receive and compare said second context number with said context identification number and (ii) output a second comparing signal indicating whether said second context number is equivalent to said context identification number;

an inverter configured to receive and complement said context select bit; and

a second matching logic gate configured to (i) receive as inputs said second comparing signal and said complement of said context select bit and (ii) output a second context matching signal to said logic unit.

17. A computer system comprising:

a bus; and

a processing unit coupled to said bus, said processing unit including

a processor requesting translation of a requested virtual address, and

a memory management unit coupled to said processor, said memory management unit including

a translation look-aside buffer including a translation table, said translation table having at least one translation table entry including a pre-stored virtual address and a context identification number, and

an address translation control circuitry, said address translation control circuit including

a primary context storage element configured to contain a first context number,

a group context storage element configured to contain a second context number,

a context matching circuit configured to receive said first context number from said primary context storage element, said second context number from said group context storage element and said context identification number from the at least one translation table entry and to output at least one context matching signal indicating whether said context identification number is equivalent to a selected context number being one of said first and second context numbers,

a comparing unit configured to compare the pre-stored virtual address with the requested virtual address and to output a comparison signal indicating whether the pre-stored virtual address is equivalent to the requested virtual address, and

a logic unit coupled to said context matching circuit and said comparing unit, said logic unit being configured to output a translation Hit signal if said context matching signal indicates that said context identification number is equivalent to said selected context number and said comparison signal indicates that the pre-stored virtual address is equivalent to the requested virtual address.

18. A method for translating a virtual address from an electronic device to a physical address through the use of a translation look-aside buffer, the method comprising the steps of:

loading a first context number into a primary context storage element;

loading a second context number into a group context storage element;

obtaining a tag portion of a translation table entry of a translation table of the translation look-aside buffer associated with the virtual address, said tag portion including a context select bit, a context identification number and a pre-stored virtual address;

selecting one of said first and second context numbers;

comparing said one of said first and second context numbers to said context identification number;

comparing said pre-stored virtual address to the virtual address;

transmitting a translation Hit signal, provided (i) said one of said first and second context numbers is equivalent to said context identification number and (ii) said pre-stored virtual address is equivalent to the virtual address.

19. The method according to claim 18 further comprising the step of

transmitting a translation Miss signal, provided (i) said one of said first and second context numbers is not equivalent to said stored context number or (ii) said stored virtual address is not equivalent to the virtual address.

20. The method according to claim 18, wherein said selecting step includes the steps of

determining a state of said context select bit;

and

selecting said second context number if said context select bit is active and alternatively selecting said first context number if said context select bit is inactive.