Hi Christophe,
On 12/2/22 00:11, Christophe Leroy wrote:
Hi Ash,
Le 11/02/2022 à 12:29, Michael Ellerman a écrit :
Ash Logan <ash@xxxxxxxxxxxx> writes:
- Like the Wii before it, the Wii U has a small amount of RAM at address
zero, a gap, then a large amount of RAM at a higher address. Instead of
the "map everything and reserve the gap" approach of the Wii, we loop
over each memblock and map only true RAM[9]. This seems to work, but as
far as I can tell is unique amongst powerpc32 platforms, so it's worth
pointing out. (Note: I've been told this doesn't work anymore after some
KUAP changes[10], so this point might be moot; haven't investigated)
We'd need more detail on that I guess. Currently all the 32-bit
platforms use the flat memory model, which assumes RAM is a single
contiguous block. Though that doesn't mean it all has to be used or
mapped, like the Wii does. To properly support your layout you should be
using sparsemem, but it's possible that's more trouble than it's worth,
I'm not sure. How far apart are the low and high blocks of RAM, and what
are their sizes?
Can you provide details on what's happening with KUAP changes ?
You are pointing to series https://lkml.org/lkml/2021/6/3/204
Does it work when CONFIG_PPC_KUAP is not selected or doesn't it work
either ?
Are you able to bisect which commit of that series is the culprit ?
Emmanuel told me about this during their work on 5.13 which I wasn't
involved in, and now can't remember any of the details, so I guess I
don't actually have any more information.
I'm working on getting a baseline setup for 5.15 (just udbg and the
like), so if there is an issue I should soon find out about it and will
get back to you.
Thanks
Christophe
Thanks,
Ash
