[openib-general] IB stack configured for kernel only support?

[Roland Dreier]

    Stan>  Will the openIB 2.6.x stack support a 'kernel only'
    Stan> configuration suitable to be run from a ramdisk (initrd)
    Stan> boot environment?  Specifically, IB startup has no
    Stan> dependencies on 'root' filesystem inodes.Will user-mode IB
    Stan> be supported in such a manner that it can be enabled/loaded
    Stan> 'after'  the kernel IB stack has been started?Case in point,
    Stan> an openSSI (www.openSSI.org) kernel creates an ICS
    Stan> (Internode Communication Subsystem) channel during the
    Stan> ramdisk (initrd) phase of kernel boot. This ICS channel is
    Stan> expected to persist thru the mounting of the root filesystem
    Stan> until kernel shutdown. For Infiniband ICS support, the
    Stan> kernel IB stack is started with connections established
    Stan> during the ramdisk (initrd) phase of system booting. If the
    Stan> user-mode IB stack requires a 'root' inode (/dev?) for ioctl
    Stan> access to kernel IB layers, then the user-mode startup must
    Stan> be delayed until the 'root' filesystem is actually
    Stan> mounted.

The kernel piece of the OpenIB stack works with no dependecies on
userspace, if it is linked into the kernel.  Obviously if modules need
to be loaded then module-init-tools and possibly hotplug and others
need to be running.  However it's pretty standard to load modules from
an initrd so even a modular stack should work.

Userspace access has not been implemented yet but it will definitely
be possible to start it after the kernel IB layer is running.

 - R.