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Index: sys/amd64/amd64/pmap.c
===================================================================
--- sys/amd64/amd64/pmap.c
+++ sys/amd64/amd64/pmap.c
@@ -4829,6 +4829,7 @@
panic("pmap_enter: invalid page directory va=%#lx", va);
origpte = *pte;
+ pv = NULL;
/*
* Is the specified virtual address already mapped?
@@ -4870,6 +4871,43 @@
goto unchanged;
goto validate;
}
+
+ /*
+ * The physical page has changed. Temporarily invalidate
+ * the mapping. This ensures that all threads sharing the
+ * pmap keep a consistent view of the mapping, which is
+ * necessary for the correct handling of COW faults. It
+ * also permits reuse of the old mapping's PV entry,
+ * avoiding an allocation.
+ *
+ * For consistency, handle unmanaged mappings the same way.
+ */
+ origpte = pte_load_clear(pte);
+ KASSERT((origpte & PG_FRAME) == opa,
+ ("pmap_enter: unexpected pa update for %#lx", va));
+ if ((origpte & PG_MANAGED) != 0) {
+ om = PHYS_TO_VM_PAGE(opa);
+
+ /*
+ * The pmap lock is sufficient to synchronize with
+ * concurrent calls to pmap_page_test_mappings() and
+ * pmap_ts_referenced().
+ */
+ if ((origpte & (PG_M | PG_RW)) == (PG_M | PG_RW))
+ vm_page_dirty(om);
+ if ((origpte & PG_A) != 0)
+ vm_page_aflag_set(om, PGA_REFERENCED);
+ CHANGE_PV_LIST_LOCK_TO_PHYS(&lock, opa);
+ pv = pmap_pvh_remove(&om->md, pmap, va);
+ if ((om->aflags & PGA_WRITEABLE) != 0 &&
+ TAILQ_EMPTY(&om->md.pv_list) &&
+ ((om->flags & PG_FICTITIOUS) != 0 ||
+ TAILQ_EMPTY(&pa_to_pvh(opa)->pv_list)))
+ vm_page_aflag_clear(om, PGA_WRITEABLE);
+ }
+ if ((origpte & PG_A) != 0)
+ pmap_invalidate_page(pmap, va);
+ origpte = 0;
} else {
/*
* Increment the counters.
@@ -4883,8 +4921,10 @@
* Enter on the PV list if part of our managed memory.
*/
if ((newpte & PG_MANAGED) != 0) {
- pv = get_pv_entry(pmap, &lock);
- pv->pv_va = va;
+ if (pv == NULL) {
+ pv = get_pv_entry(pmap, &lock);
+ pv->pv_va = va;
+ }
CHANGE_PV_LIST_LOCK_TO_PHYS(&lock, pa);
TAILQ_INSERT_TAIL(&m->md.pv_list, pv, pv_next);
m->md.pv_gen++;
@@ -4898,25 +4938,10 @@
if ((origpte & PG_V) != 0) {
validate:
origpte = pte_load_store(pte, newpte);
- opa = origpte & PG_FRAME;
- if (opa != pa) {
- if ((origpte & PG_MANAGED) != 0) {
- om = PHYS_TO_VM_PAGE(opa);
- if ((origpte & (PG_M | PG_RW)) == (PG_M |
- PG_RW))
- vm_page_dirty(om);
- if ((origpte & PG_A) != 0)
- vm_page_aflag_set(om, PGA_REFERENCED);
- CHANGE_PV_LIST_LOCK_TO_PHYS(&lock, opa);
- pmap_pvh_free(&om->md, pmap, va);
- if ((om->aflags & PGA_WRITEABLE) != 0 &&
- TAILQ_EMPTY(&om->md.pv_list) &&
- ((om->flags & PG_FICTITIOUS) != 0 ||
- TAILQ_EMPTY(&pa_to_pvh(opa)->pv_list)))
- vm_page_aflag_clear(om, PGA_WRITEABLE);
- }
- } else if ((newpte & PG_M) == 0 && (origpte & (PG_M |
- PG_RW)) == (PG_M | PG_RW)) {
+ KASSERT((origpte & PG_FRAME) == pa,
+ ("pmap_enter: unexpected pa update for %#lx", va));
+ if ((newpte & PG_M) == 0 && (origpte & (PG_M | PG_RW)) ==
+ (PG_M | PG_RW)) {
if ((origpte & PG_MANAGED) != 0)
vm_page_dirty(m);

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