Filtering coherency protocol transactions
First Claim
Patent Images
1. An apparatus comprising:
- a filter comprising;
interface circuitry to intercept coherency protocol transactions exchanged between a first master device and an interconnect for managing coherency between a first cache comprised by said first master device and at least one other cache or a second master device; and
filtering circuitry to filter the coherency protocol transactions in dependence on memory access permission data defining which regions of an address space the first master device is allowed to access;
wherein in response to an outgoing coherency protocol transaction issued from said first master device to said interconnect after a lookup in the first cache by the first master device, the filtering circuitry is configured to block the outgoing coherency protocol transaction when a memory access permission violation is detected for the outgoing coherency protocol transaction in dependence on the memory access permission data; and
wherein the filtering circuitry is configured to detect said memory access permission violation when the outgoing coherency protocol transaction is a read transaction capable of causing data to be stored in said first cache in a shareable modifiable coherency state in which coherency is to be maintained between the data in said first cache and said at least one other cache or the second master device, and the first master device is allowed to modify the data without issuing a further coherency protocol transaction to said interconnect, and the memory access permission data specifies that the first master device is;
prohibited from writing data to a region of the address space including a target address specified by the outgoing coherency protocol transaction; and
permitted to read data from said region of the address space including the target address specified by the outgoing coherency protocol transaction.
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Abstract
A filter comprises interface circuitry, to intercept coherency protocol transactions exchanged between a master device comprising a first cache and an interconnect for managing coherency between the first cache and at least one other cache or other master device. The filter has filtering circuitry for filtering the coherency protocol transactions in dependence on memory access permission data defining which regions of an address space the master device is allowed to access.
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Citations
25 Claims
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1. An apparatus comprising:
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a filter comprising; interface circuitry to intercept coherency protocol transactions exchanged between a first master device and an interconnect for managing coherency between a first cache comprised by said first master device and at least one other cache or a second master device; and filtering circuitry to filter the coherency protocol transactions in dependence on memory access permission data defining which regions of an address space the first master device is allowed to access; wherein in response to an outgoing coherency protocol transaction issued from said first master device to said interconnect after a lookup in the first cache by the first master device, the filtering circuitry is configured to block the outgoing coherency protocol transaction when a memory access permission violation is detected for the outgoing coherency protocol transaction in dependence on the memory access permission data; and wherein the filtering circuitry is configured to detect said memory access permission violation when the outgoing coherency protocol transaction is a read transaction capable of causing data to be stored in said first cache in a shareable modifiable coherency state in which coherency is to be maintained between the data in said first cache and said at least one other cache or the second master device, and the first master device is allowed to modify the data without issuing a further coherency protocol transaction to said interconnect, and the memory access permission data specifies that the first master device is; prohibited from writing data to a region of the address space including a target address specified by the outgoing coherency protocol transaction; and permitted to read data from said region of the address space including the target address specified by the outgoing coherency protocol transaction. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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25. A data processing method comprising:
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intercepting coherency protocol transactions exchanged between a first master device and an interconnect for managing coherency between a first cache comprised by said first master device and at least one other cache or a second master device; and
filtering the coherency protocol transactions in dependence on memory access permission data defining which regions of an address space the first master device is allowed to access;wherein the filtering comprises blocking an outgoing coherency protocol transaction issued from said first master device to said interconnect, when a memory access permission violation is detected for the outgoing coherency protocol transaction in dependence on the memory access permission data; wherein said memory access permission violation is detected when the outgoing coherency protocol transaction is a read transaction capable of causing data to be stored in said first cache in a shareable modifiable coherency state in which coherency is to be maintained between the data in said first cache and said at least one other cache or the second master device, and the first master device is allowed to modify the data without issuing a further coherency protocol transaction to said interconnect, and the memory access permission data specifies that the first master device is; prohibited from writing data to a region of the address space including a target address specified by the outgoing coherency protocol transaction; and permitted to read data from said region of the address space including the target address specified by the outgoing coherency protocol transaction.
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Specification