From: Christophe Leroy <christophe.leroy@csgroup.eu>
To: Michael Ellerman <mpe@ellerman.id.au>,
Ash Logan <ash@heyquark.com>,
"benh@kernel.crashing.org" <benh@kernel.crashing.org>,
"paulus@samba.org" <paulus@samba.org>
Cc: "linkmauve@linkmauve.fr" <linkmauve@linkmauve.fr>,
"linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"amd-gfx@lists.freedesktop.org" <amd-gfx@lists.freedesktop.org>,
"linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>,
"j.ne@posteo.net" <j.ne@posteo.net>
Subject: Re: [RFC] Upstreaming Linux for Nintendo Wii U
Date: Fri, 11 Feb 2022 13:11:41 +0000 [thread overview]
Message-ID: <41c696de-0e04-61e1-610c-73e9440c5c19@csgroup.eu> (raw)
In-Reply-To: <87ee49sktb.fsf@mpe.ellerman.id.au>
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 ?
Thanks
Christophe
next prev parent reply other threads:[~2022-02-11 13:11 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-07 23:34 [RFC] Upstreaming Linux for Nintendo Wii U Ash Logan
2022-02-11 11:29 ` Michael Ellerman
2022-02-11 13:11 ` Christophe Leroy [this message]
2022-02-13 23:26 ` Ash Logan
2022-02-13 23:23 ` Ash Logan
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