Date: Fri, 12 Dec 1997 19:43:11 -0500 (EST) From: "John S. Dyson" <dyson@freebsd.org> To: tlambert@primenet.com (Terry Lambert) Cc: jasone@canonware.com, jkh@time.cdrom.com, freebsd-hackers@freebsd.org Subject: Re: Beginning SPARC port Message-ID: <199712130043.TAA03452@dyson.iquest.net> In-Reply-To: <199712130002.RAA17704@usr04.primenet.com> from Terry Lambert at "Dec 13, 97 00:02:15 am"
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Terry Lambert said: > > The biggest challenge I think you will face in this phase is in > getting the VM running, and then keeping it in sync (this is where > I had problems in a PPC port I've since shelved). You will need > to get a commitment from John Dyson on working with you on this, > either to act as an information source and to get notification of > changes, or to "freeze" the VM for everything but bug fixes for > the duration of the porting process (this is what finally made me > shelve the PPC port -- I was running PPCBug firmware, so I couldn't > even leverage the NetBSD code). > You have my commitment for support, I cannot suggest to freeze the VM code due to SMP though. From the VM side, one approach might be to start with the X86 pmap. As a very rough first pass, emulate something similar to the X86 pt structure. You can do the walk of the pagetable structure when TLB exceptions occur. I don't have a Sparc manual yet, but it is likely that if you want a referenced bit, you have to emulate it. If you don't want to emulate it, I can add about 20 or so lines of code to the upper level VM so that it isn't needed for now. (Actually, it is likely that the referenced bit managment isn't needed, for a 1st pass -- get it working -- port.) I wouldn't try to make the port "perfect" in the first pass, but once it is sort-of running, it will be easier for more people to work on it. If I can get a box for a coupla K or so, I might be able to eventually help with more active coding. In any event, I'll try to be quickly available to describe code and answer questions. -- John dyson@freebsd.org jdyson@nc.com
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