Followup to: <Pine.LNX.4.44.0305090856500.9705-100000@home.transmeta.com>
By author: Linus Torvalds <torvalds@transmeta.com>
In newsgroup: linux.dev.kernel
>
> It actually does have some cost in that form, namely the fact that the
> kernel 1:1 mapping needs to be 4MB-aligned in order to take advantage of
> large-pte support. So we'd have to move the kernel to something like
> 0xc0400000 (and preferably higher, to make sure there is a nice hole in
> between - say 0xc1000000), which in turn has a cost of verifying that
> nothing assumes the current lay-out (we've had the 1/2/3GB TASK_SIZE
> patches floating around, but they've never had "odd sizes").
>
> There's another cost, which is that right now we share the pgd with the
> kernel fixmaps, and this would mean that we'd have a new one. That's just
> a single page, though.
>
> But it might "just work", and it would be interesting to see what the
> patch would look like. Hint hint.
>
Another option would be to put it in the "user" part of the address
space at 0xbffff000 (and move the %esp base value.) That would have
the nice side benefit that stuff like UML or whatever who wanted to
map something over the vsyscall could do so. Downside: each process
needs a PTE for this.
-hpa
-- <hpa@transmeta.com> at work, <hpa@zytor.com> in private! "Unix gives you enough rope to shoot yourself in the foot." Architectures needed: ia64 m68k mips64 ppc ppc64 s390 s390x sh v850 x86-64 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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