kern/46092: pmap_kenter_pa: mapping already present

[manu%netbsd.org@localhost]

>Number:         46092
>Category:       kern
>Synopsis:       pmap_kenter_pa: mapping already present
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sat Feb 25 05:50:00 +0000 2012
>Originator:     Emmanuel Dreyfus
>Release:        NetBSD-6.0_BETA
>Organization:
>Environment:
NetBSD bacasable.net.espci.fr 6.0_BETA NetBSD 6.0_BETA (XEN3_DOMU-EA) #0: Wed 
Feb 22 07:14:15 CET 2012  root@mai:/usr/src/sys/arch/i386/compile/XEN3_DOMU-EA 
i386
>Description:
An i386 Xen domU regularly complains that "pmap_kenter_pa: mapping already 
present". That was reported some time ago on mailing lists, and was commented:

By Matt Thomas <matt%3am-software.com@localhost>
> It's a bug.  The KVA used by pmap_kenter_pa should not be currently 
> mapped. I'd change it to a KASSERT and then fix it.

By "J. Hannken-Illjes" <hannken%eis.cs.tu-bs.de@localhost>
> It is a bug that should finally get its PR :-)
>
> pmap_pdp_ctor() abuses pmap_kenter_pa() to change the protection of an
> already existing mapping.  According to rmind this is because on x86
> pmap_protect() does not work for pmap_kernel().
>How-To-Repeat:
Building the tree on NetBSD-6.0/i386 domU gets the warning
>Fix: