kern/60243: pmap_reference() is superfluous

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>Number:         60243
>Category:       kern
>Synopsis:       pmap_reference() is superfluous
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          change-request
>Submitter-Id:   net
>Arrival-Date:   Sat May 09 14:10:00 +0000 2026
>Originator:     Jason Thorpe
>Release:        NetBSD 11 (and 10, and 9, and 8, and ...)
>Organization:
Pmap Debuggers International
>Environment:
N/A
>Description:
The pmap_reference() function in the pmap(9) API is superfluous.  In practice, it's only actually used in MI code for kernel sub-maps, and the kernel pmap is never deleted.  The x86 pmap also uses it internally for mod/ref attribute gathering, but this is internal logic that could be private to that pmap.

Because of this superfluous API, all pmap implementations are required to maintain a reference count that is essentially unused.

>How-To-Repeat:
N/A
>Fix:
G/C it from the general pmap API.