Author: alc
Date: Sun Dec 29 05:36:01 2019
New Revision: 356168
URL: https://svnweb.freebsd.org/changeset/base/356168
Log:
Correctly implement PMAP_ENTER_NOREPLACE in pmap_enter_{l2,pde}() on kernel
mappings.
Reduce code duplication by defining a function, pmap_abort_ptp(), for
handling a common error case.
Simplify error handling in pmap_enter_quick_locked().
Reviewed by: kib
Tested by: pho
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D22890
Modified:
head/sys/i386/i386/pmap.c
Modified: head/sys/i386/i386/pmap.c
==============================================================================
--- head/sys/i386/i386/pmap.c Sun Dec 29 04:58:27 2019 (r356167)
+++ head/sys/i386/i386/pmap.c Sun Dec 29 05:36:01 2019 (r356168)
@@ -314,6 +314,7 @@ static pv_entry_t pmap_pvh_remove(struct md_page *pvh,
vm_offset_t va);
static int pmap_pvh_wired_mappings(struct md_page *pvh, int count);
+static void pmap_abort_ptp(pmap_t pmap, vm_offset_t va, vm_page_t mpte);
static boolean_t pmap_demote_pde(pmap_t pmap, pd_entry_t *pde, vm_offset_t va);
static bool pmap_enter_4mpage(pmap_t pmap, vm_offset_t va, vm_page_t m,
vm_prot_t prot);
@@ -2008,6 +2009,27 @@ pmap_unuse_pt(pmap_t pmap, vm_offset_t va, struct spgl
}
/*
+ * Release a page table page reference after a failed attempt to create a
+ * mapping.
+ */
+static void
+pmap_abort_ptp(pmap_t pmap, vm_offset_t va, vm_page_t mpte)
+{
+ struct spglist free;
+
+ SLIST_INIT(&free);
+ if (pmap_unwire_ptp(pmap, mpte, &free)) {
+ /*
+ * Although "va" was never mapped, paging-structure caches
+ * could nonetheless have entries that refer to the freed
+ * page table pages. Invalidate those entries.
+ */
+ pmap_invalidate_page_int(pmap, va);
+ vm_page_free_pages_toq(&free, true);
+ }
+}
+
+/*
* Initialize the pmap for the swapper process.
*/
static void
@@ -3895,6 +3917,24 @@ pmap_enter_4mpage(pmap_t pmap, vm_offset_t va, vm_page
}
/*
+ * Returns true if every page table entry in the page table page that maps
+ * the specified kernel virtual address is zero.
+ */
+static bool
+pmap_every_pte_zero(vm_offset_t va)
+{
+ pt_entry_t *pt_end, *pte;
+
+ KASSERT((va & PDRMASK) == 0, ("va is misaligned"));
+ pte = vtopte(va);
+ for (pt_end = pte + NPTEPG; pte < pt_end; pte++) {
+ if (*pte != 0)
+ return (false);
+ }
+ return (true);
+}
+
+/*
* Tries to create the specified 2 or 4 MB page mapping. Returns KERN_SUCCESS
* if the mapping was created, and either KERN_FAILURE or
* KERN_RESOURCE_SHORTAGE otherwise. Returns KERN_FAILURE if
@@ -3921,7 +3961,9 @@ pmap_enter_pde(pmap_t pmap, vm_offset_t va, pd_entry_t
pde = pmap_pde(pmap, va);
oldpde = *pde;
if ((oldpde & PG_V) != 0) {
- if ((flags & PMAP_ENTER_NOREPLACE) != 0) {
+ if ((flags & PMAP_ENTER_NOREPLACE) != 0 && (pmap !=
+ kernel_pmap || (oldpde & PG_PS) != 0 ||
+ !pmap_every_pte_zero(va))) {
CTR2(KTR_PMAP, "pmap_enter_pde: failure for va %#lx"
" in pmap %p", va, pmap);
return (KERN_FAILURE);
@@ -3940,8 +3982,14 @@ pmap_enter_pde(pmap_t pmap, vm_offset_t va, pd_entry_t
if (pmap_remove_ptes(pmap, va, va + NBPDR, &free))
pmap_invalidate_all_int(pmap);
}
- vm_page_free_pages_toq(&free, true);
- if (pmap == kernel_pmap) {
+ if (pmap != kernel_pmap) {
+ vm_page_free_pages_toq(&free, true);
+ KASSERT(*pde == 0, ("pmap_enter_pde: non-zero pde %p",
+ pde));
+ } else {
+ KASSERT(SLIST_EMPTY(&free),
+ ("pmap_enter_pde: freed kernel page table page"));
+
/*
* Both pmap_remove_pde() and pmap_remove_ptes() will
* leave the kernel page table page zero filled.
@@ -3949,9 +3997,7 @@ pmap_enter_pde(pmap_t pmap, vm_offset_t va, pd_entry_t
mt = PHYS_TO_VM_PAGE(*pde & PG_FRAME);
if (pmap_insert_pt_page(pmap, mt, false))
panic("pmap_enter_pde: trie insert failed");
- } else
- KASSERT(*pde == 0, ("pmap_enter_pde: non-zero pde %p",
- pde));
+ }
}
if ((newpde & PG_MANAGED) != 0) {
/*
@@ -3982,8 +4028,8 @@ pmap_enter_pde(pmap_t pmap, vm_offset_t va, pd_entry_t
pde_store(pde, newpde);
pmap_pde_mappings++;
- CTR2(KTR_PMAP, "pmap_enter_pde: success for va %#lx"
- " in pmap %p", va, pmap);
+ CTR2(KTR_PMAP, "pmap_enter_pde: success for va %#lx in pmap %p",
+ va, pmap);
return (KERN_SUCCESS);
}
@@ -4055,7 +4101,6 @@ pmap_enter_quick_locked(pmap_t pmap, vm_offset_t va, v
vm_prot_t prot, vm_page_t mpte)
{
pt_entry_t newpte, *pte;
- struct spglist free;
KASSERT(pmap != kernel_pmap || va < kmi.clean_sva ||
va >= kmi.clean_eva || (m->oflags & VPO_UNMANAGED) != 0,
@@ -4106,12 +4151,10 @@ pmap_enter_quick_locked(pmap_t pmap, vm_offset_t va, v
sched_pin();
pte = pmap_pte_quick(pmap, va);
if (*pte) {
- if (mpte != NULL) {
+ if (mpte != NULL)
mpte->ref_count--;
- mpte = NULL;
- }
sched_unpin();
- return (mpte);
+ return (NULL);
}
/*
@@ -4119,17 +4162,10 @@ pmap_enter_quick_locked(pmap_t pmap, vm_offset_t va, v
*/
if ((m->oflags & VPO_UNMANAGED) == 0 &&
!pmap_try_insert_pv_entry(pmap, va, m)) {
- if (mpte != NULL) {
- SLIST_INIT(&free);
- if (pmap_unwire_ptp(pmap, mpte, &free)) {
- pmap_invalidate_page_int(pmap, va);
- vm_page_free_pages_toq(&free, true);
- }
-
- mpte = NULL;
- }
+ if (mpte != NULL)
+ pmap_abort_ptp(pmap, va, mpte);
sched_unpin();
- return (mpte);
+ return (NULL);
}
/*
@@ -4351,7 +4387,6 @@ static void
__CONCAT(PMTYPE, copy)(pmap_t dst_pmap, pmap_t src_pmap, vm_offset_t dst_addr,
vm_size_t len, vm_offset_t src_addr)
{
- struct spglist free;
pt_entry_t *src_pte, *dst_pte, ptetemp;
pd_entry_t srcptepaddr;
vm_page_t dstmpte, srcmpte;
@@ -4432,14 +4467,7 @@ __CONCAT(PMTYPE, copy)(pmap_t dst_pmap, pmap_t src_pma
PG_A);
dst_pmap->pm_stats.resident_count++;
} else {
- SLIST_INIT(&free);
- if (pmap_unwire_ptp(dst_pmap, dstmpte,
- &free)) {
- pmap_invalidate_page_int(
- dst_pmap, addr);
- vm_page_free_pages_toq(&free,
- true);
- }
+ pmap_abort_ptp(dst_pmap, addr, dstmpte);
goto out;
}
if (dstmpte->ref_count >= srcmpte->ref_count)
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