Method for providing remote access redirect capability in a channel adapter of a system area network
View Patent ↗A method for providing remote access redirect in a host channel adapter of a system area network are provided. The method provides a mechanism by which a host channel adapter, in response to receiving a marker message, places selected channel(s) of the host channel adapter in a remote access redirect (RAR) mode of operation. During the RAR mode of operation, memory access messages received by the host channel adapter that are destined for portions of an application memory space marked as being protected are converted to RAR receive messages and redirected to a queue pair associated with an operating system rather than the queue pair for the application. The operating system is responsible for serializing access to application memory pages outside of the host channel adapter. The mechanisms of the present invention may be used to perform a checkpoint data integrity operation.
1. A computer implemented method, in a system area network endnode, for modifying the operation of a host channel adapter, the computer implemented method comprising:
receiving a marker message in the host channel adapter, wherein the marker message is an immediate marker message that is interpreted by the host channel adapter;
determining, in the host channel adapter, a type of the marker message, wherein the type of the marker message is one of a remote access redirect mode enable marker message, a remote access redirect mode disable marker message, a pause sending-receiving marker message, and a resume sending-receiving marker message, wherein the host channel adapter remains in the remote access redirect mode of operation until a remote access redirect mode disable marker message is received; and
responsive to determining that the type of the marker message is the remote access redirect mode enable marker message, placing the host channel adapter in a remote access redirect mode of operation, wherein the remote access redirect mode of operation converts memory access messages into receive messages, and wherein the remote access redirect mode of operation further causes access requests to the protected portions of system memory to be redirected to software running in a host system, wherein the access requests are redirected to software running in the host system by converting the access requests to receive work requests that are posted to a queue pair associated with the software, and wherein the queue pair associated with the software is a different queue pair than a queue pair associated with an application with which the channel communicates.
2. The computer implemented method of claim 1 , wherein the host channel adapter pauses sending-receiving of messages over a channel until a resume sending-receiving marker message associated with the channel is received.
3. The computer implemented method of claim 1 , wherein the software running in the host system is an operating system.
4. The computer implemented method of claim 3 , wherein upon receiving an access request to a protected portion of system memory, the operating system performs a copy-on-write remap of the protected portion.
5. The computer implemented method of claim 4 , wherein the operating system updates a translation table in the host channel adapter responsive to performing the copy-on-write remap.