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Index: sys/i386/i386/pmap.c
===================================================================
--- sys/i386/i386/pmap.c
+++ sys/i386/i386/pmap.c
@@ -3466,11 +3466,14 @@
PMAP_LOCK(pmap);
sched_pin();
- /*
- * In the case that a page table page is not
- * resident, we are creating it here.
- */
+ pde = pmap_pde(pmap, va);
if (va < VM_MAXUSER_ADDRESS) {
+ /*
+ * va is for UVA.
+ * In the case that a page table page is not resident,
+ * we are creating it here. pmap_allocpte() handles
+ * demotion.
+ */
mpte = pmap_allocpte(pmap, va, flags);
if (mpte == NULL) {
KASSERT((flags & PMAP_ENTER_NOSLEEP) != 0,
@@ -3480,19 +3483,28 @@
PMAP_UNLOCK(pmap);
return (KERN_RESOURCE_SHORTAGE);
}
+ } else {
+ /*
+ * va is for KVA, so pmap_demote_pde() will never fail
+ * to install a page table page. PG_V is also
+ * asserted by pmap_demote_pde().
+ */
+ KASSERT(pde != NULL && (*pde & PG_V) != 0,
+ ("KVA %#x invalid pde pdir %#jx", va,
+ (uintmax_t)pmap->pm_pdir[PTDPTDI]));
+ if ((*pde & PG_PS) != 0)
+ pmap_demote_pde(pmap, pde, va);
}
-
- pde = pmap_pde(pmap, va);
- if ((*pde & PG_PS) != 0)
- panic("pmap_enter: attempted pmap_enter on 4MB page");
pte = pmap_pte_quick(pmap, va);
/*
- * Page Directory table entry not valid, we need a new PT page
+ * Page Directory table entry is not valid, which should not
+ * happen. We should have either allocated the page table
+ * page or demoted the existing mapping above.
*/
if (pte == NULL) {
panic("pmap_enter: invalid page directory pdir=%#jx, va=%#x",
- (uintmax_t)pmap->pm_pdir[PTDPTDI], va);
+ (uintmax_t)pmap->pm_pdir[PTDPTDI], va);
}
pa = VM_PAGE_TO_PHYS(m);

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