[openib-general] Default of MSI on when MSI support is configured into the kernel

[Roland Dreier]

    Robert> Is there any reason that we cannot just change the mtcha
    Robert> driver to use MSI by default when CONFIG_PCI_MSI is
    Robert> configured in the kernel ?  People that don't support or
    Robert> want to use MSI can always disable it when the build their
    Robert> kernel, or override the values when they do the modprobe.

It seems that at least the latest Fedora kernels for x86-64 turns on
CONFIG_PCI_MSI, which means that turning MSI on would break things on
Opteron systems using AMD-8131 PCI-X bridges.  I think having the
default be safe but possibly not maximum peformance is better than
being broken on some systems.  It should be possible to extend the
interrupt test in the latest driver to set MSI automatically.
Eventually I may code this up, or someone industrious can do it sooner.

 - R.