Date: Thu, 9 Apr 2015 09:19:43 -0700 From: Adrian Chadd <adrian@freebsd.org> To: =?UTF-8?Q?Pierre=2DYves_P=C3=A9neau?= <Pierre-Yves.Peneau@lip6.fr> Cc: FreeBSD Questions <freebsd-questions@freebsd.org> Subject: Re: How FreeBSD manage more than 4GB on 32 bits architecture Message-ID: <CAJ-Vmo=e1F1rHRW82r5uwJ5f-vOhZ1qKMbSsM4E0aomzQ=4=UQ@mail.gmail.com> In-Reply-To: <55269509.1080103@asim.lip6.fr> References: <5526408F.1090005@asim.lip6.fr> <20150409114941.692910293a8120de4dafd400@yahoo.es> <20150409114906.6dd4379c@archlinux> <55264DC5.9070606@asim.lip6.fr> <55267A63.4040503@qeng-ho.org> <55269509.1080103@asim.lip6.fr>
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Hi! This sounds... very exciting. I'd start by taking a look at how PAE works - you may be able to reuse all those pieces and just implement more than the 4 bits of physical address space. The interesting bits of PAE aren't just the extension of the physical addresses, but all the management of mapping things into virtual address space as required. I haven't looked at the MIPS side of things though. IIRC, on MIPS32 we only implement up to what the direct map KSEG supports, so a little PAE ish work would be required there to make things work right. So, I'd start by looking at how PAE on i386 works. I think there's a little bit of KVA exhaustion going on in -HEAD with i386 PAE that can be fixed with a little bit of attention. The rest of the basic PAE stuff should still work fine. Then if you need it for MIPS, you'll need to sketch out how you expect PAE to work on MIPS, and then make up a project for that. :) -adrian
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