Introduce dummy pagers for 'special' subsystems using UVM objects.

Some pmaps (x86, hppa) and the buffer cache rely on UVM objects to allocate
and manipulate pages.  These objects should not be manipulated by uvm_fault()
and do not currently require the same locking enforcement.

Use the dummy pagers to explicitly document which UVM functions are meant to
manipulate UVM objects (uobj) that do not need the upcoming `vmobjlock' and
instead still rely on the KERNEL_LOCK().

Tested by many as part of a larger diff.

ok kettenis@, beck@

1 files changed, 3 insertions, 3 deletions

diff --git a/sys/arch/i386/i386/pmap.c b/sys/arch/i386/i386/pmap.c
index a11178c8b63..b5521e15775 100644
--- a/sys/arch/i386/i386/pmap.c
+++ b/sys/arch/i386/i386/pmap.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: pmap.c,v 1.214 2021/06/16 09:02:21 mpi Exp $	*/
+/*	$OpenBSD: pmap.c,v 1.215 2021/09/05 11:44:46 mpi Exp $	*/
 /*	$NetBSD: pmap.c,v 1.91 2000/06/02 17:46:37 thorpej Exp $	*/
 
 /*
@@ -963,7 +963,7 @@ pmap_bootstrap(vaddr_t kva_start)
 	kpm = pmap_kernel();
 	mtx_init(&kpm->pm_mtx, -1); /* must not be used */
 	mtx_init(&kpm->pm_apte_mtx, IPL_VM);
-	uvm_obj_init(&kpm->pm_obj, NULL, 1);
+	uvm_obj_init(&kpm->pm_obj, &pmap_pager, 1);
 	bzero(&kpm->pm_list, sizeof(kpm->pm_list));  /* pm_list not used */
 	kpm->pm_pdir = (vaddr_t)(proc0.p_addr->u_pcb.pcb_cr3 + KERNBASE);
 	kpm->pm_pdirpa = proc0.p_addr->u_pcb.pcb_cr3;
@@ -1348,7 +1348,7 @@ pmap_create(void)
 	mtx_init(&pmap->pm_apte_mtx, IPL_VM);
 
 	/* init uvm_object */
-	uvm_obj_init(&pmap->pm_obj, NULL, 1);
+	uvm_obj_init(&pmap->pm_obj, &pmap_pager, 1);
 	pmap->pm_stats.wired_count = 0;
 	pmap->pm_stats.resident_count = 1;	/* count the PDP allocd below */
 	pmap->pm_ptphint = NULL;