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Index: sys/amd64/amd64/pmap.c
===================================================================
--- sys/amd64/amd64/pmap.c
+++ sys/amd64/amd64/pmap.c
@@ -614,10 +614,12 @@
static void free_pv_chunk(struct pv_chunk *pc);
static void free_pv_entry(pmap_t pmap, pv_entry_t pv);
-static pv_entry_t get_pv_entry(pmap_t pmap, struct rwlock **lockp);
+static pv_entry_t get_pv_entry(pmap_t pmap, vm_offset_t va,
+ struct rwlock **lockp);
static int popcnt_pc_map_pq(uint64_t *map);
-static vm_page_t reclaim_pv_chunk(pmap_t locked_pmap, struct rwlock **lockp);
-static void reserve_pv_entries(pmap_t pmap, int needed,
+static vm_page_t reclaim_pv_chunk(pmap_t locked_pmap, vm_offset_t skip_va,
+ struct rwlock **lockp);
+static void reserve_pv_entries(pmap_t pmap, vm_offset_t skip_va, int needed,
struct rwlock **lockp);
static void pmap_pv_demote_pde(pmap_t pmap, vm_offset_t va, vm_paddr_t pa,
struct rwlock **lockp);
@@ -3174,7 +3176,9 @@
/*
* We are in a serious low memory condition. Resort to
* drastic measures to free some pages so we can allocate
- * another pv entry chunk.
+ * another pv entry chunk. Do not free a PV entry for skip_va from
+ * the specified pmap since the caller may be attempting to update
+ * the corresponding page table entry.
*
* Returns NULL if PV entries were reclaimed from the specified pmap.
*
@@ -3183,7 +3187,7 @@
* exacerbating the shortage of free pv entries.
*/
static vm_page_t
-reclaim_pv_chunk(pmap_t locked_pmap, struct rwlock **lockp)
+reclaim_pv_chunk(pmap_t locked_pmap, vm_offset_t skip_va, struct rwlock **lockp)
{
struct pv_chunk *pc, *pc_marker, *pc_marker_end;
struct pv_chunk_header pc_marker_b, pc_marker_end_b;
@@ -3287,6 +3291,8 @@
bit = bsfq(inuse);
pv = &pc->pc_pventry[field * 64 + bit];
va = pv->pv_va;
+ if (pmap == locked_pmap && va == skip_va)
+ continue;
pde = pmap_pde(pmap, va);
if ((*pde & PG_PS) != 0)
continue;
@@ -3428,15 +3434,15 @@
}
/*
- * Returns a new PV entry, allocating a new PV chunk from the system when
- * needed. If this PV chunk allocation fails and a PV list lock pointer was
- * given, a PV chunk is reclaimed from an arbitrary pmap. Otherwise, NULL is
- * returned.
+ * Returns a new PV entry for the specified virtual address, allocating a new
+ * PV chunk from the system when needed. If this PV chunk allocation fails
+ * and a PV list lock pointer was given, a PV chunk is reclaimed from an
+ * arbitrary pmap. Otherwise, NULL is returned.
*
* The given PV list lock may be released.
*/
static pv_entry_t
-get_pv_entry(pmap_t pmap, struct rwlock **lockp)
+get_pv_entry(pmap_t pmap, vm_offset_t va, struct rwlock **lockp)
{
int bit, field;
pv_entry_t pv;
@@ -3456,6 +3462,7 @@
}
if (field < _NPCM) {
pv = &pc->pc_pventry[field * 64 + bit];
+ pv->pv_va = va;
pc->pc_map[field] &= ~(1ul << bit);
/* If this was the last item, move it to tail */
if (pc->pc_map[0] == 0 && pc->pc_map[1] == 0 &&
@@ -3477,7 +3484,7 @@
PV_STAT(pc_chunk_tryfail++);
return (NULL);
}
- m = reclaim_pv_chunk(pmap, lockp);
+ m = reclaim_pv_chunk(pmap, va, lockp);
if (m == NULL)
goto retry;
}
@@ -3493,6 +3500,7 @@
TAILQ_INSERT_TAIL(&pv_chunks, pc, pc_lru);
mtx_unlock(&pv_chunks_mutex);
pv = &pc->pc_pventry[0];
+ pv->pv_va = va;
TAILQ_INSERT_HEAD(&pmap->pm_pvchunk, pc, pc_list);
PV_STAT(atomic_add_long(&pv_entry_count, 1));
PV_STAT(atomic_add_int(&pv_entry_spare, _NPCPV - 1));
@@ -3530,12 +3538,15 @@
/*
* Ensure that the number of spare PV entries in the specified pmap meets or
- * exceeds the given count, "needed".
+ * exceeds the given count, "needed". If it becomes necessary to reclaim a PV
+ * chunk in order to satisfy the reservation, do not reclaim a PV entry for
+ * skip_va.
*
* The given PV list lock may be released.
*/
static void
-reserve_pv_entries(pmap_t pmap, int needed, struct rwlock **lockp)
+reserve_pv_entries(pmap_t pmap, vm_offset_t skip_va, int needed,
+ struct rwlock **lockp)
{
struct pch new_tail;
struct pv_chunk *pc;
@@ -3572,7 +3583,7 @@
m = vm_page_alloc(NULL, 0, VM_ALLOC_NORMAL | VM_ALLOC_NOOBJ |
VM_ALLOC_WIRED);
if (m == NULL) {
- m = reclaim_pv_chunk(pmap, lockp);
+ m = reclaim_pv_chunk(pmap, skip_va, lockp);
if (m == NULL)
goto retry;
}
@@ -3754,8 +3765,7 @@
PMAP_LOCK_ASSERT(pmap, MA_OWNED);
/* Pass NULL instead of the lock pointer to disable reclamation. */
- if ((pv = get_pv_entry(pmap, NULL)) != NULL) {
- pv->pv_va = va;
+ if ((pv = get_pv_entry(pmap, va, NULL)) != NULL) {
CHANGE_PV_LIST_LOCK_TO_VM_PAGE(lockp, m);
TAILQ_INSERT_TAIL(&m->md.pv_list, pv, pv_next);
m->md.pv_gen++;
@@ -3779,10 +3789,9 @@
PMAP_LOCK_ASSERT(pmap, MA_OWNED);
/* Pass NULL instead of the lock pointer to disable reclamation. */
- if ((pv = get_pv_entry(pmap, (flags & PMAP_ENTER_NORECLAIM) != 0 ?
+ if ((pv = get_pv_entry(pmap, va, (flags & PMAP_ENTER_NORECLAIM) != 0 ?
NULL : lockp)) == NULL)
return (false);
- pv->pv_va = va;
pa = pde & PG_PS_FRAME;
CHANGE_PV_LIST_LOCK_TO_PHYS(lockp, pa);
pvh = pa_to_pvh(pa);
@@ -3918,7 +3927,7 @@
* PV entry for the 2MB page mapping that is being demoted.
*/
if ((oldpde & PG_MANAGED) != 0)
- reserve_pv_entries(pmap, NPTEPG - 1, lockp);
+ reserve_pv_entries(pmap, va, NPTEPG - 1, lockp);
/*
* Demote the mapping. This pmap is locked. The old PDE has
@@ -4873,8 +4882,7 @@
* 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;
+ pv = get_pv_entry(pmap, va, &lock);
CHANGE_PV_LIST_LOCK_TO_PHYS(&lock, pa);
TAILQ_INSERT_TAIL(&m->md.pv_list, pv, pv_next);
m->md.pv_gen++;

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