From: "H. Peter Anvin" <hpa@zytor.com>
To: linux-kernel@vger.kernel.org
Subject: Re: [PATCH] i386 uaccess to fixmap pages
Date: 9 May 2003 20:26:40 -0700 [thread overview]
Message-ID: <b9hrhg$5v7$1@cesium.transmeta.com> (raw)
In-Reply-To: Pine.LNX.4.44.0305090856500.9705-100000@home.transmeta.com
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
next prev parent reply other threads:[~2003-05-10 3:14 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-05-09 2:03 [PATCH] i386 uaccess to fixmap pages Roland McGrath
2003-05-09 4:31 ` Andrew Morton
2003-05-09 8:55 ` Roland McGrath
2003-05-09 9:19 ` Andrew Morton
2003-05-09 9:40 ` Roland McGrath
2003-05-09 10:43 ` Roland McGrath
2003-05-09 11:42 ` Dave Jones
2003-05-09 11:55 ` Alan Cox
2003-05-09 12:40 ` Jamie Lokier
2003-05-09 16:06 ` Linus Torvalds
2003-05-09 16:38 ` Dave Hansen
2003-05-09 15:55 ` Martin J. Bligh
2003-05-09 18:20 ` William Lee Irwin III
2003-05-09 16:48 ` Linus Torvalds
2003-05-09 17:16 ` Dave Hansen
2003-05-10 3:26 ` H. Peter Anvin [this message]
2003-05-10 15:31 ` Jamie Lokier
2003-05-10 17:23 ` Ulrich Drepper
2003-05-10 19:23 ` H. Peter Anvin
2003-05-10 20:52 ` Jamie Lokier
2003-05-09 17:28 Chuck Ebbert
2003-05-09 17:49 ` Linus Torvalds
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