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diff --git a/sys/amd64/amd64/pmap.c b/sys/amd64/amd64/pmap.c
--- a/sys/amd64/amd64/pmap.c
+++ b/sys/amd64/amd64/pmap.c
@@ -1276,7 +1276,7 @@
static void pmap_update_pde_invalidate(pmap_t, vm_offset_t va, pd_entry_t pde);
static vm_page_t _pmap_allocpte(pmap_t pmap, vm_pindex_t ptepindex,
- struct rwlock **lockp, vm_offset_t va);
+ struct rwlock **lockp, vm_offset_t va, bool first_level);
static pd_entry_t *pmap_alloc_pde(pmap_t pmap, vm_offset_t va, vm_page_t *pdpgp,
struct rwlock **lockp);
static vm_page_t pmap_allocpte(pmap_t pmap, vm_offset_t va,
@@ -4167,8 +4167,8 @@
pml5index = pmap_pml5e_index(va);
pml5 = &pmap->pm_pmltop[pml5index];
if ((*pml5 & PG_V) == 0) {
- if (_pmap_allocpte(pmap, pmap_pml5e_pindex(va), lockp, va) ==
- NULL)
+ if (_pmap_allocpte(pmap, pmap_pml5e_pindex(va), lockp, va,
+ false) == NULL)
return (NULL);
allocated = true;
} else {
@@ -4204,8 +4204,8 @@
if ((*pml4 & PG_V) == 0) {
/* Have to allocate a new pdp, recurse */
- if (_pmap_allocpte(pmap, pmap_pml4e_pindex(va), lockp, va) ==
- NULL) {
+ if (_pmap_allocpte(pmap, pmap_pml4e_pindex(va), lockp, va,
+ false) == NULL) {
if (pmap_is_la57(pmap))
pmap_allocpte_free_unref(pmap, va,
pmap_pml5e(pmap, va));
@@ -4231,12 +4231,11 @@
* This routine is called if the desired page table page does not exist.
*
* If page table page allocation fails, this routine may sleep before
- * returning NULL. It sleeps only if a lock pointer was given.
- *
- * Note: If a page allocation fails at page table level two, three, or four,
- * up to three pages may be held during the wait, only to be released
- * afterwards. This conservative approach is easily argued to avoid
- * race conditions.
+ * returning NULL. It sleeps only if a lock pointer was given. Sleep
+ * occurs right before returning from the first recursion level, which
+ * is indicated by the first_level parameter. This way, we never sleep
+ * with a page table page having ref_count == 0, otherwise the page could
+ * be freed under us.
*
* The ptepindexes, i.e. page indices, of the page table pages encountered
* while translating virtual address va are defined as follows:
@@ -4272,7 +4271,7 @@
*/
static vm_page_t
_pmap_allocpte(pmap_t pmap, vm_pindex_t ptepindex, struct rwlock **lockp,
- vm_offset_t va __unused)
+ vm_offset_t va __unused, bool first_level)
{
vm_pindex_t pml5index, pml4index;
pml5_entry_t *pml5, *pml5u;
@@ -4293,21 +4292,8 @@
* Allocate a page table page.
*/
if ((m = vm_page_alloc(NULL, ptepindex, VM_ALLOC_NOOBJ |
- VM_ALLOC_WIRED | VM_ALLOC_ZERO)) == NULL) {
- if (lockp != NULL) {
- RELEASE_PV_LIST_LOCK(lockp);
- PMAP_UNLOCK(pmap);
- PMAP_ASSERT_NOT_IN_DI();
- vm_wait(NULL);
- PMAP_LOCK(pmap);
- }
-
- /*
- * Indicate the need to retry. While waiting, the page table
- * page may have been allocated.
- */
- return (NULL);
- }
+ VM_ALLOC_WIRED | VM_ALLOC_ZERO)) == NULL)
+ goto wait;
if ((m->flags & PG_ZERO) == 0)
pmap_zero_page(m);
@@ -4339,7 +4325,7 @@
if (pml4 == NULL) {
vm_page_unwire_noq(m);
vm_page_free_zero(m);
- return (NULL);
+ goto wait;
}
KASSERT((*pml4 & PG_V) == 0,
("pmap %p va %#lx pml4 %#lx", pmap, va, *pml4));
@@ -4367,7 +4353,7 @@
if (pdp == NULL) {
vm_page_unwire_noq(m);
vm_page_free_zero(m);
- return (NULL);
+ goto wait;
}
KASSERT((*pdp & PG_V) == 0,
("pmap %p va %#lx pdp %#lx", pmap, va, *pdp));
@@ -4378,17 +4364,17 @@
if (pdp == NULL) {
vm_page_unwire_noq(m);
vm_page_free_zero(m);
- return (NULL);
+ goto wait;
}
if ((*pdp & PG_V) == 0) {
/* Have to allocate a new pd, recurse */
if (_pmap_allocpte(pmap, pmap_pdpe_pindex(va),
- lockp, va) == NULL) {
+ lockp, va, false) == NULL) {
pmap_allocpte_free_unref(pmap, va,
pmap_pml4e(pmap, va));
vm_page_unwire_noq(m);
vm_page_free_zero(m);
- return (NULL);
+ goto wait;
}
} else {
/* Add reference to the pd page */
@@ -4405,8 +4391,22 @@
}
pmap_resident_count_inc(pmap, 1);
-
return (m);
+
+wait:
+ if (first_level && lockp != NULL) {
+ RELEASE_PV_LIST_LOCK(lockp);
+ PMAP_UNLOCK(pmap);
+ PMAP_ASSERT_NOT_IN_DI();
+ vm_wait(NULL);
+ PMAP_LOCK(pmap);
+ }
+
+ /*
+ * Indicate the need to retry. While waiting, the page table
+ * page may have been allocated.
+ */
+ return (NULL);
}
static pd_entry_t *
@@ -4433,7 +4433,7 @@
} else if (va < VM_MAXUSER_ADDRESS) {
/* Allocate a pd page. */
pdpindex = pmap_pde_pindex(va) >> NPDPEPGSHIFT;
- pdpg = _pmap_allocpte(pmap, NUPDE + pdpindex, lockp, va);
+ pdpg = _pmap_allocpte(pmap, NUPDE + pdpindex, lockp, va, true);
if (pdpg == NULL) {
if (lockp != NULL)
goto retry;
@@ -4494,7 +4494,7 @@
* Here if the pte page isn't mapped, or if it has been
* deallocated.
*/
- m = _pmap_allocpte(pmap, ptepindex, lockp, va);
+ m = _pmap_allocpte(pmap, ptepindex, lockp, va, true);
if (m == NULL && lockp != NULL)
goto retry;
}
@@ -6514,7 +6514,7 @@
pml4e = pmap_pml4e(pmap, va);
if (pml4e == NULL || (*pml4e & PG_V) == 0) {
mp = _pmap_allocpte(pmap, pmap_pml4e_pindex(va),
- NULL, va);
+ NULL, va, true);
if (mp == NULL)
goto allocf;
pdpe = (pdp_entry_t *)PHYS_TO_DMAP(VM_PAGE_TO_PHYS(mp));
@@ -6535,7 +6535,7 @@
pde = pmap_pde(pmap, va);
if (pde == NULL) {
mp = _pmap_allocpte(pmap, pmap_pdpe_pindex(va),
- NULL, va);
+ NULL, va, true);
if (mp == NULL)
goto allocf;
pde = (pd_entry_t *)PHYS_TO_DMAP(VM_PAGE_TO_PHYS(mp));
@@ -6690,7 +6690,7 @@
*/
nosleep = (flags & PMAP_ENTER_NOSLEEP) != 0;
mpte = _pmap_allocpte(pmap, pmap_pde_pindex(va),
- nosleep ? NULL : &lock, va);
+ nosleep ? NULL : &lock, va, true);
if (mpte == NULL && nosleep) {
rv = KERN_RESOURCE_SHORTAGE;
goto out;
@@ -7174,7 +7174,7 @@
* pointer, because we don't intend to sleep.
*/
mpte = _pmap_allocpte(pmap, ptepindex, NULL,
- va);
+ va, true);
if (mpte == NULL)
return (mpte);
}
@@ -7503,8 +7503,8 @@
pdpe = pmap_pdpe(dst_pmap, addr);
if (pdpe == NULL) {
if (_pmap_allocpte(dst_pmap,
- pmap_pml4e_pindex(addr), NULL, addr) ==
- NULL)
+ pmap_pml4e_pindex(addr), NULL, addr,
+ true) == NULL)
break;
pdpe = pmap_pdpe(dst_pmap, addr);
} else {

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