Re: [net-2.6 PATCH] ixgbe: add IntMode module parameter

[David Miller <davem@davemloft.net>]

From: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Date: Sun, 18 Apr 2010 22:03:59 -0700

> This patch adds the IntMode module parameter to ixgbe to allow
> user selection of interrupt mode (MSI-X, MSI, legacy) on driver
> load.  To work around the errata described above, ixgbe needs to
> be able to disable MSI-X for affected configurations.

This is not how we handle situations like this.

Here is one acceptable way to handle this:

Turn MSI/MSI-X off for every system that uses this PCI-E
complex chipset.  Add a whitelist that allows enabling.

Here is another:

Turn MSI/MSI-X on by default and have blacklists.

Anything that requires unusual user interactions, such as specifying
special module parameters, for correct operations is absolutely
unacceptable.

I don't want to hear how difficult it is to determine whether a
system will hit this bug or not.  If it's hard, just turn MSI
off unconditionally with this chipset until you can detect things
properly.