[src/netbsd-9]: src/sys/arch/x86/x86 Apply patch, requested by bouyer in tick...

[martin <martin%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/597ea7cab6a1
branches:  netbsd-9
changeset: 938167:597ea7cab6a1
user:      martin <martin%NetBSD.org@localhost>
date:      Thu Sep 03 13:45:24 2020 +0000

description:
Apply patch, requested by bouyer in ticket #1075:

        sys/arch/x86/x86/pmap.c (apply patch)

Fix double count on ptp entries in pmap_enter_gnt(), which causes a KASSERT
at pmap_destroy() time. Call pmap_free_ptp() if needed. We can have a 0 wire
count if we had an old mapping and grant map hypercall failed,
and this was the only page in this ptp.

while there remove ptp != NULL checks for gnt operations: we always have
a ptp here.

diffstat:

 sys/arch/x86/x86/pmap.c |  25 ++++++++++---------------
 1 files changed, 10 insertions(+), 15 deletions(-)

diffs (70 lines):

diff -r 1182635c531c -r 597ea7cab6a1 sys/arch/x86/x86/pmap.c
--- a/sys/arch/x86/x86/pmap.c   Thu Sep 03 13:38:29 2020 +0000
+++ b/sys/arch/x86/x86/pmap.c   Thu Sep 03 13:45:24 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: pmap.c,v 1.334.2.4 2020/09/02 12:40:06 martin Exp $    */
+/*     $NetBSD: pmap.c,v 1.334.2.5 2020/09/03 13:45:24 martin Exp $    */
 
 /*
  * Copyright (c) 2008, 2010, 2016, 2017 The NetBSD Foundation, Inc.
@@ -130,7 +130,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: pmap.c,v 1.334.2.4 2020/09/02 12:40:06 martin Exp $");
+__KERNEL_RCSID(0, "$NetBSD: pmap.c,v 1.334.2.5 2020/09/03 13:45:24 martin Exp $");
 
 #include "opt_user_ldt.h"
 #include "opt_lockdebug.h"
@@ -4559,28 +4559,21 @@
        if (__predict_false(op->status != GNTST_okay)) {
                printf("%s: GNTTABOP_map_grant_ref status: %d\n",
                    __func__, op->status);
-               if (ptp != NULL) {
-                       if (have_oldpa) {
-                               ptp->wire_count--;
-                       }
+               if (have_oldpa) {
+                       ptp->wire_count--;
                }
        } else {
                pgnt->pd_gnt_refs++;
-               if (ptp != NULL) {
-                       if (!have_oldpa) {
-                               ptp->wire_count++;
-                       }
+               if (!have_oldpa) {
+                       ptp->wire_count++;
                }
+               KASSERT(ptp->wire_count > 1);
        }
 
        /*
         * Update statistics and PTP's reference count.
         */
        pmap_stats_update_bypte(pmap, 0, opte);
-       if (ptp != NULL && !have_oldpa) {
-               ptp->wire_count++;
-       }
-       KASSERT(ptp == NULL || ptp->wire_count > 1);
 
        /*
         * If old page is pv-tracked, remove pv_entry from its list.
@@ -4599,6 +4592,8 @@
                old_pve = pmap_remove_pv(old_pp, ptp, va);
                old_pp->pp_attrs |= pmap_pte_to_pp_attrs(opte);
        }
+       if (ptp->wire_count <= 1)
+               pmap_free_ptp(pmap, ptp, va, ptes, pdes);
 
        pmap_unmap_ptes(pmap, pmap2);
 
@@ -4687,7 +4682,7 @@
                 * being used, free it!
                 */
 
-               if (ptp && ptp->wire_count <= 1)
+               if (ptp->wire_count <= 1)
                        pmap_free_ptp(pmap, ptp, va, ptes, pdes);
        }
        pmap_unmap_ptes(pmap, pmap2); /* unlock pmap */