[ofa-general] MTHCA driver for Linux

[Roland Dreier]

 > If I keep ib_mthca driver in kernel while shutting down the DomU, the next
 > start of the DomU resets the machine.
 > 
 > Trivial fix is possible: either to rmmod ib_mthca before shutting down the
 > DomU or set .shutdown section to the same value as the .remove section in
 > pci_driver structure.
 > 
 > Are you willing apply a patch that sets .shutdown in the mainline of IB driver
 > in Linux? Or is it something that should be fixed by Xen guys?

I would like to understand the underlying problem before blindly
setting the .shutdown method of the ib_mthca PCI driver section.  The
mthca driver should be able to handle the hardware being in an
arbitrary state when it is reloaded -- that is why it resets the
adapter very early during initialization.  Do you have any idea what
is going wrong in the case where the machine resets?

Very few other PCI drivers have a .shutdown method, and I don't know
of any that just duplicate the .remove method.  So rather than just
having a bandaid for mthca that probably leaves the same problem for
every other driver, I would prefer to understand the problem first,
and if it is indeed something specific to mthca, then fix the
underlying issue in mthca with a simpler shutdown method.

I guess one way to debug this would be to delete operations from
mthca_remove_one() one by one (starting from the end of the function),
and each time try restarting your domU after doing rmmod ib_mthca.
When you reach the really necessary thing, then you'll see the reset.

 - R.