kern/60522: evbppc/RB800 hits MI pmap KASSERT failure

["rokuyama.rk%gmail.com@localhost via gnats" <gnats-admin%NetBSD.org@localhost>]

>Number:         60522
>Category:       kern
>Synopsis:       evbppc/RB800 hits MI pmap KASSERT failure
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sat Aug 01 03:55:00 +0000 2026
>Originator:     Rin Okuyama
>Release:        11.9.7
>Organization:
Internet Initiative Japan Inc.
>Environment:
NetBSD rb800.local 11.99.7 NetBSD 11.99.7 (RB800-$Revision: 1.41 $) #9: Sat Aug  1 11:40:53 JST 2026  rin@sakaizumii.local:/home/rin/src/sys/arch/evbppc/compile/RB800 evbppc
>Description:
On RB800 with option INSECURE enabled, a KASSERT in MI pmap fires:

```
# cd /usr/tests/dev/fss && atf-run
(snip)
tp-start: 1785555213.589886, t_fss, 1
tc-start: 1785555213.589970, basic
[ 136.6130204] panic: kernel diagnostic assertion "!VM_PAGEMD_PVLIST_EMPTY_P(mdpg)" failed: file "../../../../uvm/pmap/pmap.c", line 1330
[ 136.6348717] cpu0: Begin traceback...
[ 136.6348717] 0x00d3e9d0: at vpanic+0x154
[ 136.6432136] 0x00d3ea00: at kern_assert+0x60
[ 136.6432136] 0x00d3ea40: at pmap_pte_protect+0x210
[ 136.6538985] 0x00d3ea70: at pmap_pte_process+0x68
[ 136.6538985] 0x00d3eaa0: at pmap_protect+0x70
[ 136.6638310] 0x00d3eac0: at uvm_map_protect+0x268
[ 136.6638310] 0x00d3eb10: at kobj_affix+0x1f4
[ 136.6737622] 0x00d3eb30: at module_do_load+0x4ec
[ 136.6737622] 0x00d3ebf0: at module_autoload+0x108
[ 136.6846379] 0x00d3ec10: at spec_open+0x354
[ 136.6846379] 0x00d3ec90: at VOP_OPEN+0x4c
[ 136.6938266] 0x00d3ecc0: at vn_open+0x188
[ 136.6938266] 0x00d3ede0: at do_open+0xac
[ 136.6938266] 0x00d3ee40: at do_sys_openat+0x9c
[ 136.7052636] 0x00d3ee80: at sys_open+0x2c
[ 136.7052636] 0x00d3eeb0: at syscall+0x110
[ 136.7151053] 0x00d3ef20: user SC trap #5 by 0xfdbf84ac: srr1=0x2d030
[ 136.7242392]             r1=0xffff76d0 cr=0x20042242 xer=0 ctr=0xfdbf84a4
[ 136.7242392] cpu0: End traceback...
Stopped in pid 1211.1211 (fssconfig) at netbsd:cpu_Debugger+0xc:        tw
0, r1, r1
db>
```
>How-To-Repeat:
Described above.
>Fix:
N/A