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

Michael Ellerman michael at ellerman.id.au
Wed Jun 13 15:18:07 EST 2012

On Tue, 2012-06-05 at 12:47 +1000, Anton Blanchard wrote:
> Hi,
> > On Mon, 2012-06-04 at 16:43 +1000, Michael Ellerman wrote:
> > > 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.


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