Messages in this thread | | | Date | Mon, 14 Feb 2022 10:26:47 +1100 | Subject | Re: [RFC] Upstreaming Linux for Nintendo Wii U | From | Ash Logan <> |
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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@heyquark.com> 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
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