Author: kib
Date: Fri May 31 18:53:04 2019
New Revision: 348476
URL: https://svnweb.freebsd.org/changeset/base/348476
Log:
Simplify flow of pmap_demote_pde_locked() and add more comprehensive
debugging checks.
In particular,
- Move the code to handle failure to allocate page table page into
a helper.
- After the previous item is done, it is possible to distinguish !PG_A
case and case of missed page, in the control flow.
- Make the variable to indicate that in-kernel mapping is demoted.
- Assert that missed page table page can only happen for in-kernel
mapping when demoting direct map.
- If DIAGNOSTIC is enabled, and the page table page should be already
filled, check all ptes instead of only first one.
Reviewed by: alc, markj
Tested by: pho (previous version)
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D20266
Modified:
head/sys/amd64/amd64/pmap.c
Modified: head/sys/amd64/amd64/pmap.c
==============================================================================
--- head/sys/amd64/amd64/pmap.c Fri May 31 18:46:35 2019 (r348475)
+++ head/sys/amd64/amd64/pmap.c Fri May 31 18:53:04 2019 (r348476)
@@ -4490,6 +4490,50 @@ pmap_demote_pde(pmap_t pmap, pd_entry_t *pde, vm_offse
return (rv);
}
+static void
+pmap_demote_pde_check(pt_entry_t *firstpte __unused, pt_entry_t newpte
__unused)
+{
+#ifdef INVARIANTS
+#ifdef DIAGNOSTIC
+ pt_entry_t *xpte, *ypte;
+
+ for (xpte = firstpte; xpte < firstpte + NPTEPG;
+ xpte++, newpte += PAGE_SIZE) {
+ if ((*xpte & PG_FRAME) != (newpte & PG_FRAME)) {
+ printf("pmap_demote_pde: xpte %zd and newpte map "
+ "different pages: found %#lx, expected %#lx\n",
+ xpte - firstpte, *xpte, newpte);
+ printf("page table dump\n");
+ for (ypte = firstpte; ypte < firstpte + NPTEPG; ypte++)
+ printf("%zd %#lx\n", ypte - firstpte, *ypte);
+ panic("firstpte");
+ }
+ }
+#else
+ KASSERT((*firstpte & PG_FRAME) == (newpte & PG_FRAME),
+ ("pmap_demote_pde: firstpte and newpte map different physical"
+ " addresses"));
+#endif
+#endif
+}
+
+static void
+pmap_demote_pde_abort(pmap_t pmap, vm_offset_t va, pd_entry_t *pde,
+ pd_entry_t oldpde, struct rwlock **lockp)
+{
+ struct spglist free;
+ vm_offset_t sva;
+
+ SLIST_INIT(&free);
+ sva = trunc_2mpage(va);
+ pmap_remove_pde(pmap, pde, sva, &free, lockp);
+ if ((oldpde & pmap_global_bit(pmap)) == 0)
+ pmap_invalidate_pde_page(pmap, sva, oldpde);
+ vm_page_free_pages_toq(&free, true);
+ CTR2(KTR_PMAP, "pmap_demote_pde: failure for va %#lx in pmap %p",
+ va, pmap);
+}
+
static boolean_t
pmap_demote_pde_locked(pmap_t pmap, pd_entry_t *pde, vm_offset_t va,
struct rwlock **lockp)
@@ -4499,12 +4543,11 @@ pmap_demote_pde_locked(pmap_t pmap, pd_entry_t *pde, v
pt_entry_t PG_A, PG_G, PG_M, PG_PKU_MASK, PG_RW, PG_V;
vm_paddr_t mptepa;
vm_page_t mpte;
- struct spglist free;
- vm_offset_t sva;
int PG_PTE_CACHE;
+ bool in_kernel;
- PG_G = pmap_global_bit(pmap);
PG_A = pmap_accessed_bit(pmap);
+ PG_G = pmap_global_bit(pmap);
PG_M = pmap_modified_bit(pmap);
PG_RW = pmap_rw_bit(pmap);
PG_V = pmap_valid_bit(pmap);
@@ -4512,42 +4555,59 @@ pmap_demote_pde_locked(pmap_t pmap, pd_entry_t *pde, v
PG_PKU_MASK = pmap_pku_mask_bit(pmap);
PMAP_LOCK_ASSERT(pmap, MA_OWNED);
+ in_kernel = va >= VM_MAXUSER_ADDRESS;
oldpde = *pde;
KASSERT((oldpde & (PG_PS | PG_V)) == (PG_PS | PG_V),
("pmap_demote_pde: oldpde is missing PG_PS and/or PG_V"));
- if ((oldpde & PG_A) == 0 || (mpte = pmap_remove_pt_page(pmap, va)) ==
- NULL) {
+
+ /*
+ * Invalidate the 2MB page mapping and return "failure" if the
+ * mapping was never accessed.
+ */
+ if ((oldpde & PG_A) == 0) {
+ pmap_demote_pde_abort(pmap, va, pde, oldpde, lockp);
+ return (FALSE);
+ }
+
+ mpte = pmap_remove_pt_page(pmap, va);
+ if (mpte == NULL) {
KASSERT((oldpde & PG_W) == 0,
("pmap_demote_pde: page table page for a wired mapping"
" is missing"));
/*
- * Invalidate the 2MB page mapping and return "failure" if the
- * mapping was never accessed or the allocation of the new
- * page table page fails. If the 2MB page mapping belongs to
- * the direct map region of the kernel's address space, then
- * the page allocation request specifies the highest possible
- * priority (VM_ALLOC_INTERRUPT). Otherwise, the priority is
- * normal. Page table pages are preallocated for every other
- * part of the kernel address space, so the direct map region
- * is the only part of the kernel address space that must be
- * handled here.
+ * If the page table page is missing and the mapping
+ * is for a kernel address, the mapping must belong to
+ * the direct map. Page table pages are preallocated
+ * for every other part of the kernel address space,
+ * so the direct map region is the only part of the
+ * kernel address space that must be handled here.
*/
- if ((oldpde & PG_A) == 0 || (mpte = vm_page_alloc(NULL,
- pmap_pde_pindex(va), (va >= DMAP_MIN_ADDRESS && va <
- DMAP_MAX_ADDRESS ? VM_ALLOC_INTERRUPT : VM_ALLOC_NORMAL) |
- VM_ALLOC_NOOBJ | VM_ALLOC_WIRED)) == NULL) {
- SLIST_INIT(&free);
- sva = trunc_2mpage(va);
- pmap_remove_pde(pmap, pde, sva, &free, lockp);
- if ((oldpde & PG_G) == 0)
- pmap_invalidate_pde_page(pmap, sva, oldpde);
- vm_page_free_pages_toq(&free, true);
- CTR2(KTR_PMAP, "pmap_demote_pde: failure for va %#lx"
- " in pmap %p", va, pmap);
+ KASSERT(!in_kernel || (va >= DMAP_MIN_ADDRESS &&
+ va < DMAP_MAX_ADDRESS),
+ ("pmap_demote_pde: No saved mpte for va %#lx", va));
+
+ /*
+ * If the 2MB page mapping belongs to the direct map
+ * region of the kernel's address space, then the page
+ * allocation request specifies the highest possible
+ * priority (VM_ALLOC_INTERRUPT). Otherwise, the
+ * priority is normal.
+ */
+ mpte = vm_page_alloc(NULL, pmap_pde_pindex(va),
+ (in_kernel ? VM_ALLOC_INTERRUPT : VM_ALLOC_NORMAL) |
+ VM_ALLOC_NOOBJ | VM_ALLOC_WIRED);
+
+ /*
+ * If the allocation of the new page table page fails,
+ * invalidate the 2MB page mapping and return "failure".
+ */
+ if (mpte == NULL) {
+ pmap_demote_pde_abort(pmap, va, pde, oldpde, lockp);
return (FALSE);
}
- if (va < VM_MAXUSER_ADDRESS) {
+
+ if (!in_kernel) {
mpte->wire_count = NPTEPG;
pmap_resident_count_inc(pmap, 1);
}
@@ -4569,9 +4629,7 @@ pmap_demote_pde_locked(pmap_t pmap, pd_entry_t *pde, v
if ((oldpde & PG_PROMOTED) == 0)
pmap_fill_ptp(firstpte, newpte);
- KASSERT((*firstpte & PG_FRAME) == (newpte & PG_FRAME),
- ("pmap_demote_pde: firstpte and newpte map different physical"
- " addresses"));
+ pmap_demote_pde_check(firstpte, newpte);
/*
* If the mapping has changed attributes, update the page table
@@ -4606,7 +4664,7 @@ pmap_demote_pde_locked(pmap_t pmap, pd_entry_t *pde, v
/*
* Invalidate a stale recursive mapping of the page table page.
*/
- if (va >= VM_MAXUSER_ADDRESS)
+ if (in_kernel)
pmap_invalidate_page(pmap, (vm_offset_t)vtopte(va));
/*
@@ -4616,8 +4674,8 @@ pmap_demote_pde_locked(pmap_t pmap, pd_entry_t *pde, v
pmap_pv_demote_pde(pmap, va, oldpde & PG_PS_FRAME, lockp);
atomic_add_long(&pmap_pde_demotions, 1);
- CTR2(KTR_PMAP, "pmap_demote_pde: success for va %#lx"
- " in pmap %p", va, pmap);
+ CTR2(KTR_PMAP, "pmap_demote_pde: success for va %#lx in pmap %p",
+ va, pmap);
return (TRUE);
}
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