On 29.10.20 11:49, Renato Mancuso wrote:
> Hi Jan, Andrea,
> 
> Thanks for looping me in on this topic!
> 
> Just a not that I in my version I don't just recreate the root page, but
> the entire page table tree to be NC for the SMMU. That immediately gave
> me a stable system on the ZCU102. I have tested that even with a
> dynamically recolored root cell. I haven't tested with colored
> DMA-capable inmates, but I'll do that soon as I have just added support
> to boot colored Linux inmates. I keep SMMU and CPU tables in sync by
> duplicating any change in map/unmap operations at cell creation time.

That recreation is what we do for VT-d vs. VT-x as well because tables
are incompatible (at least in the VT-d version we support). On AMD, that
is not needed, and I thought that the ARM tables were designed to enable
the same. How does Linux handle this?

> 
> @Jan, when I started working on my current repo, I did it to quickly
> port JH to a dev board I quickly needed to work on (the NXP S32V234). It
> just so happened that I branched out quite a bit. I am quite happy if
> some of my effort helps with upstream dev. I just don't have too many
> cycles at the moment to propose well thought out patches. I am actually
> looking forward to having this conversation in a few weeks.

Understood, but "quickly" is relative in such complex topics. The more
people can look at a common code base and share thoughts, the better and
really quicker is the result. As you may know, the SMMU implementation
of NXP had a long out-of-tree history as well, unfortunately.

Same applies to the coloring topic, so I'm also looking forward to get
central traction on that soon, hopefully.

Jan

-- 
Siemens AG, T RDA IOT
Corporate Competence Center Embedded Linux

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