Subject: Re: remplacing page mappings behind uvm
To: YAMAMOTO Takashi <>
From: Manuel Bouyer <>
List: tech-kern
Date: 12/01/2007 14:44:49
On Sat, Dec 01, 2007 at 10:23:40PM +0900, YAMAMOTO Takashi wrote:
> i think the easiest fix for the problem which started this thread
> is making libxc (back) to use non-anonymous mapping.
> as far as you mmap a valid object (either kernfs file or device,
> i prefer the latter), uvm_unmap calls pmap_remove for you.

I agree that we should have a valid object (at last a valid map entry,
which, as things are now, probably means a valid object). But I'm not sure
at all that mmaping a device to get the object at mmap time rather than
ioctl time makes things easiers. This doesn't fix the problems with the
ioctl, and introduce some more issues (like, we can't provide physical
addresses to udv_attach() or udv_fault() because these are not physical
adresses, and we don't even have them at the time of mmap).

And this issue also needs to be solved in netbsd-4, I want to keep
binary compatibility here.

Manuel Bouyer <>
     NetBSD: 26 ans d'experience feront toujours la difference