Intel Provides Linux PCI Express NTB Support
Intel has provided Linux kernel support for PCI Express Non-Transparent Bridges (NTB). PCI-E NTB allows for interconnecting multiple systems using PCI Express.
Jon Mason, one of the Intel engineers working on the Linux PCI Express Non-Transparent Bridge support, has a fairly lengthy commit message on his patch that describes this PCI-E bridge:
A PCI-Express non-transparent bridge (NTB) is a point-to-point PCIe bus connecting 2 systems, providing electrical isolation between the two subsystems. A non-transparent bridge is functionally similar to a transparent bridge except that both sides of the bridge have their own independent address domains. The host on one side of the bridge will not have the visibility of the complete memory or I/O space on the other side of the bridge. To communicate across the non-transparent bridge, each NTB endpoint has one (or more) apertures exposed to the local system. Writes to these apertures are mirrored to memory on the remote system. Communications can also occur through the use of doorbell registers that initiate interrupts to the alternate domain, and scratch-pad registers accessible from both sides.This PCI Express technology isn't new, but is now finding its way to be supported by the mainline Linux kernel -- hopefully for the Linux 3.6 kernel.
A second patch by Jon Mason on Friday provides a virtual Ethernet device using the NTB transport API for sending and receiving data.
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