Snooping With Access Permissions

The data processing apparatus according to claim 6, wherein:

• the receive circuitry is further adapted to receive a snoop response from the target;
• and
• the processing circuitry is further adapted:
• if the snoop response contains the data, to cause the transmit circuitry to forward the data to the requester, and
• otherwise, to cause the transmit circuitry to transmit a request for the data from a main memory and in response to receiving the data from the main memory, to forward the data to the requester.

A data processing apparatus, further comprising:

• receive circuitry to receive a request to access data at an access address from a requester;
• processing circuitry to generate a forwarding snoop request, wherein the forwarding snoop request causes a target to forward the data to the requester;
• and
• transmit circuitry to send the forwarding snoop request to the target
• permission obtaining circuitry to obtain, for one or more address ranges, an access permission of the target, wherein
• the forwarding snoop request is capable of indicating one or more access permissions of the target in relation to the data;
• the permission obtaining circuitry is adapted, in response to receiving the request to access data, to obtain a permission corresponding to one of the one or more address ranges that encompasses the access address range as the one or more access permissions, and
• wherein the processing circuitry is further adapted to generate the forwarding snoop request comprising the one or more access permissions.

A method comprising:

• receiving a request to access data at an access address from a requester;
• generating a forwarding snoop request, wherein the forwarding snoop request causes a target to forward the data to the requester;
• sending the forwarding snoop request to the target,
• obtaining, for one or more address ranges, an access permission of the target, wherein
• the forwarding snoop request is capable of indicating one or more access permissions of the target in relation to the data;
• in response to receiving the request to access data, a permission corresponding to one of the one or more address ranges that encompasses the access address range is obtained as the one or more access permissions;
• and
• the forwarding snoop request is generated to contain the one or more access permissions.

A data processing apparatus comprising:

• receive circuitry to receive a forwarding snoop request from a home node to provide data at an access address to a requester;
• permission obtaining circuitry to obtain, for one or more address ranges, an access permission of a target of the forwarding snoop request;
• and
• transmit circuitry to transmit an outgoing snoop request to the target of the forwarding snoop request,
• wherein the permission obtaining circuitry is adapted, in response to receiving the request to access data, to obtain a permission corresponding to one of the one or more address ranges that encompasses the access address range as the one or more access permissions, and
• wherein a type of the outgoing snoop request is based on the corresponding permission.

A method comprising:

• receiving a forwarding snoop request from a home node to provide data at an access address to a requester;
• storing, for one or more address ranges, an access permission of a target of the forwarding snoop request;
• transmitting an outgoing snoop request to the target of the forwarding snoop request;
• determining, in response to receiving the request to access data, one of the one or more address ranges that encompasses the access address range;
• and
• acquiring a corresponding permission as the one or more access permissions,
• wherein a type of the outgoing snoop request is based on the corresponding permission.

A data processing apparatus comprising:

• receive circuitry to receive a forwarding snoop request from a home node to provide data at an access address to a requester, wherein the forwarding snoop request is capable of indicating one or more access permissions of the data processing apparatus in relation to the data;
• cache circuitry to store the data together with associated modification indicator;
• and
• transmit circuitry to transmit a snoop response based on the one or more access permissions and the modification indicator.

A method comprising:

• receiving a forwarding snoop request from a home node to provide data at an access address to a requester, wherein the forwarding snoop request is capable of indicating one or more access permissions of a data processing apparatus in relation to the data;
• storing the data together with associated modification indicator;
• and
• transmitting a snoop response based on the one or more access permissions and the modification indicator.