Re: [PATCH] powerpc: pseries: Round up MSI-X requests

On Tue, 2012-06-05 at 12:47 +1000, Anton Blanchard wrote:

Hi,

quoted

On Mon, 2012-06-04 at 16:43 +1000, Michael Ellerman wrote:

quoted

There is some chance this will result in breakage because the driver
asks for N - and assumes that is what was allocated - and the
device is configured for > N.

We can fix that. We can whack the configuration back with N, just know
that we have "allocated"  > N.

I think whacking config space is more likely to break something than
just configuring more than the driver asked for.

I agree we don't want to be giving back a larger value than requested.
There's only one place that can happen in theory and since firmware only
returns power of two values I dont think it will happen in practise.

Don't follow you here.

Even so do we want to do something like this (as yet untested)? If the
rounded up request fails we retry with the original request.

Yes we do. Had a chance to test it?

The pseries msi free code just sets our vectors to 0 so it doesn't need
to know how many were originally allocated.

Yep, looks like it will cope.

We only create virqs for what's in pdev->msi_list, which will be what
the driver originally asked for, and we free all those by walking the
list again. So the fact that firmware allocated a few extra for us is
OK, we have nothing extra to cleanup.

cheers