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[src/trunk]: src/sys/arch/x86/x86 in pmap_get_ptp(), if we need to allocate m...
details: https://anonhg.NetBSD.org/src/rev/32bd1379ca7c
branches: trunk
changeset: 822236:32bd1379ca7c
user: chs <chs%NetBSD.org@localhost>
date: Thu Mar 09 00:21:55 2017 +0000
description:
in pmap_get_ptp(), if we need to allocate multiple new ptp levels
and succeed in allocating some pages but fail to get them all,
free any ptps we did allocate before returning.
also, only consume kernel-reserve pages if pmap_enter()
is called without PMAP_CANFAIL set, to help avoid deadlocking
during high memory pressure.
diffstat:
sys/arch/x86/x86/pmap.c | 132 +++++++++++++++++++++++++++++------------------
1 files changed, 80 insertions(+), 52 deletions(-)
diffs (247 lines):
diff -r 8ebacdc01fec -r 32bd1379ca7c sys/arch/x86/x86/pmap.c
--- a/sys/arch/x86/x86/pmap.c Thu Mar 09 00:18:23 2017 +0000
+++ b/sys/arch/x86/x86/pmap.c Thu Mar 09 00:21:55 2017 +0000
@@ -1,4 +1,4 @@
-/* $NetBSD: pmap.c,v 1.241 2017/03/05 08:36:35 maxv Exp $ */
+/* $NetBSD: pmap.c,v 1.242 2017/03/09 00:21:55 chs Exp $ */
/*-
* Copyright (c) 2008, 2010, 2016, 2017 The NetBSD Foundation, Inc.
@@ -171,7 +171,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: pmap.c,v 1.241 2017/03/05 08:36:35 maxv Exp $");
+__KERNEL_RCSID(0, "$NetBSD: pmap.c,v 1.242 2017/03/09 00:21:55 chs Exp $");
#include "opt_user_ldt.h"
#include "opt_lockdebug.h"
@@ -551,7 +551,7 @@
#endif
static struct vm_page *pmap_get_ptp(struct pmap *, vaddr_t,
- pd_entry_t * const *);
+ pd_entry_t * const *, int);
static struct vm_page *pmap_find_ptp(struct pmap *, vaddr_t, paddr_t, int);
static void pmap_freepage(struct pmap *, struct vm_page *, int);
static void pmap_free_ptp(struct pmap *, struct vm_page *, vaddr_t,
@@ -1966,51 +1966,61 @@
*/
static struct vm_page *
-pmap_get_ptp(struct pmap *pmap, vaddr_t va, pd_entry_t * const *pdes)
+pmap_get_ptp(struct pmap *pmap, vaddr_t va, pd_entry_t * const *pdes, int flags)
{
- struct vm_page *ptp, *pptp;
- int i;
+ struct vm_page *ptp;
+ struct {
+ struct vm_page *pg;
+ bool new;
+ } pt[PTP_LEVELS + 1];
+ int i, aflags;
unsigned long index;
pd_entry_t *pva;
- paddr_t ppa, pa;
+ paddr_t pa;
struct uvm_object *obj;
+ voff_t off;
KASSERT(pmap != pmap_kernel());
KASSERT(mutex_owned(pmap->pm_lock));
KASSERT(kpreempt_disabled());
- ptp = NULL;
- pa = (paddr_t)-1;
+ /*
+ * Loop through all page table levels allocating a page
+ * for any level where we don't already have one.
+ */
+ memset(pt, 0, sizeof(pt));
+ aflags = ((flags & PMAP_CANFAIL) ? 0 : UVM_PGA_USERESERVE) |
+ UVM_PGA_ZERO;
+ for (i = PTP_LEVELS; i > 1; i--) {
+ obj = &pmap->pm_obj[i - 2];
+ off = ptp_va2o(va, i - 1);
+
+ PMAP_SUBOBJ_LOCK(pmap, i - 2);
+ pt[i].pg = uvm_pagelookup(obj, off);
+ if (pt[i].pg == NULL) {
+ pt[i].pg = uvm_pagealloc(obj, off, NULL, aflags);
+ pt[i].new = true;
+ }
+ PMAP_SUBOBJ_UNLOCK(pmap, i - 2);
+
+ if (pt[i].pg == NULL)
+ goto fail;
+ }
/*
- * Loop through all page table levels seeing if we need to
- * add a new page to that level.
+ * Now that we have all the pages looked up or allocated,
+ * loop through again installing any new ones into the tree.
*/
for (i = PTP_LEVELS; i > 1; i--) {
- /*
- * Save values from previous round.
- */
- pptp = ptp;
- ppa = pa;
-
index = pl_i(va, i);
pva = pdes[i - 2];
if (pmap_valid_entry(pva[index])) {
- ppa = pmap_pte2pa(pva[index]);
- ptp = NULL;
+ KASSERT(!pt[i].new);
continue;
}
- obj = &pmap->pm_obj[i-2];
- PMAP_SUBOBJ_LOCK(pmap, i - 2);
- ptp = uvm_pagealloc(obj, ptp_va2o(va, i - 1), NULL,
- UVM_PGA_USERESERVE|UVM_PGA_ZERO);
- PMAP_SUBOBJ_UNLOCK(pmap, i - 2);
-
- if (ptp == NULL)
- return NULL;
-
+ ptp = pt[i].pg;
ptp->flags &= ~PG_BUSY; /* never busy */
ptp->wire_count = 1;
pmap->pm_ptphint[i - 2] = ptp;
@@ -2019,6 +2029,7 @@
(pmap_pa2pte(pa) | PG_u | PG_RW | PG_V));
#if defined(XEN) && defined(__x86_64__)
if (i == PTP_LEVELS) {
+
/*
* Update the per-cpu PD on all cpus the current
* pmap is active on
@@ -2028,31 +2039,37 @@
#endif
pmap_pte_flush();
pmap_stats_update(pmap, 1, 0);
+
/*
* If we're not in the top level, increase the
* wire count of the parent page.
*/
if (i < PTP_LEVELS) {
- if (pptp == NULL) {
- pptp = pmap_find_ptp(pmap, va, ppa, i);
- KASSERT(pptp != NULL);
- }
- pptp->wire_count++;
+ pt[i + 1].pg->wire_count++;
}
}
+ ptp = pt[2].pg;
+ KASSERT(ptp != NULL);
+ pmap->pm_ptphint[0] = ptp;
+ return ptp;
/*
- * PTP is not NULL if we just allocated a new PTP. If it is
- * still NULL, we must look up the existing one.
+ * Allocation of a ptp failed, free any others that we just allocated.
*/
- if (ptp == NULL) {
- ptp = pmap_find_ptp(pmap, va, ppa, 1);
- KASSERTMSG(ptp != NULL, "pmap_get_ptp: va %" PRIxVADDR
- "ppa %" PRIxPADDR "\n", va, ppa);
+fail:
+ for (i = PTP_LEVELS; i > 1; i--) {
+ if (pt[i].pg == NULL) {
+ break;
+ }
+ if (!pt[i].new) {
+ continue;
+ }
+ obj = &pmap->pm_obj[i - 2];
+ PMAP_SUBOBJ_LOCK(pmap, i - 2);
+ uvm_pagefree(pt[i].pg);
+ PMAP_SUBOBJ_UNLOCK(pmap, i - 2);
}
-
- pmap->pm_ptphint[0] = ptp;
- return ptp;
+ return NULL;
}
/*
@@ -2309,6 +2326,22 @@
}
/*
+ * pmap_check_ptps: verify that none of the pmap's page table objects
+ * have any pages allocated to them.
+ */
+
+static inline void
+pmap_check_ptps(struct pmap *pmap)
+{
+ int i;
+
+ for (i = 0; i < PTP_LEVELS - 1; i++) {
+ KASSERT(pmap->pm_obj[i].uo_npages == 0);
+ KASSERT(TAILQ_EMPTY(&pmap->pm_obj[i].memq));
+ }
+}
+
+/*
* pmap_destroy: drop reference count on pmap. free pmap if
* reference count goes to zero.
*/
@@ -2327,6 +2360,7 @@
*/
l = curlwp;
if (__predict_false(l->l_md.md_gc_pmap == pmap)) {
+ pmap_check_ptps(pmap);
if (uvmexp.free < uvmexp.freetarg) {
pmap_update(pmap);
} else {
@@ -2387,15 +2421,6 @@
pmap_free_ptps(pmap->pm_gc_ptp);
- /*
- * destroyed pmap shouldn't have remaining PTPs
- */
-
- for (i = 0; i < PTP_LEVELS - 1; i++) {
- KASSERT(pmap->pm_obj[i].uo_npages == 0);
- KASSERT(TAILQ_EMPTY(&pmap->pm_obj[i].memq));
- }
-
pool_cache_put(&pmap_pdp_cache, pmap->pm_pdir);
#ifdef USER_LDT
@@ -2424,6 +2449,8 @@
#ifdef XEN
kcpuset_destroy(pmap->pm_xen_ptp_cpus);
#endif
+
+ pmap_check_ptps(pmap);
pool_cache_put(&pmap_cache, pmap);
}
@@ -4086,7 +4113,7 @@
if (pmap == pmap_kernel()) {
ptp = NULL;
} else {
- ptp = pmap_get_ptp(pmap, va, pdes);
+ ptp = pmap_get_ptp(pmap, va, pdes, flags);
if (ptp == NULL) {
pmap_unmap_ptes(pmap, pmap2);
if (flags & PMAP_CANFAIL) {
@@ -4506,6 +4533,7 @@
l->l_md.md_gc_pmap = NULL;
pmap_tlb_shootdown(pmap, (vaddr_t)-1LL, 0, TLBSHOOT_UPDATE);
}
+
/*
* Initiate any pending TLB shootdowns. Wait for them to
* complete before returning control to the caller.
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