Subject: Re: Generic IOMMU pooled allocator

From: Sowmini Varadhan <[email-masked]>
Date: Sun, 22 Mar 2015 18:07:08 -0400

On (03/23/15 09:02), Benjamin Herrenschmidt wrote:
> > How does this relate to the ARM implementation? There is currently
> > an effort going on to make that one shared with ARM64 and possibly
> > x86. Has anyone looked at both the PowerPC and ARM ways of doing the
> > allocation to see if we could pick one of the two to work on
> > all architectures?
> 
> What I see in ARM is horribly complex, I can't quite make sense of it
> in a couple of minutes of looking at it, and doesn't seem to address the
> basic issue we are addressing here which is the splitting of the iommu
> table lock.

Amen to that.. I thought it was just me :-)

I plan to go through the code to see if/where the armd iommu code
does its locking and achieves its parallelism, but the mapping
between the sparc/powerpc approach and armd is not immediately obvious
to me.

--Sowmini