From baea70e2d240e48edbd021981532b9d16f16589b Mon Sep 17 00:00:00 2001
From: jeff <jeff@FreeBSD.org>
Date: Mon, 5 Aug 2013 00:28:03 +0000
Subject:  - Introduce a specific function, pmap_remove_kernel_pde, for
 removing    huge pages in the kernel's address space.  This works around
 several    asserts from pmap_demote_pde_locked that did not apply and gave
 false    warnings.

Discovered by:	pho
Reviewed by:	alc
Sponsored by:	EMC / Isilon Storage Division
---
 sys/amd64/amd64/pmap.c | 41 +++++++++++++++++++++++++++++++++++++++--
 sys/i386/i386/pmap.c   | 41 +++++++++++++++++++++++++++++++++++++++--
 2 files changed, 78 insertions(+), 4 deletions(-)

diff --git a/sys/amd64/amd64/pmap.c b/sys/amd64/amd64/pmap.c
index d7e125b..46112b5 100644
--- a/sys/amd64/amd64/pmap.c
+++ b/sys/amd64/amd64/pmap.c
@@ -2795,6 +2795,44 @@ pmap_demote_pde_locked(pmap_t pmap, pd_entry_t *pde, vm_offset_t va,
 }
 
 /*
+ * pmap_remove_kernel_pde: Remove a kernel superpage mapping.
+ */
+static void
+pmap_remove_kernel_pde(pmap_t pmap, pd_entry_t *pde, vm_offset_t va)
+{
+	pd_entry_t newpde;
+	vm_paddr_t mptepa;
+	vm_page_t mpte;
+
+	PMAP_LOCK_ASSERT(pmap, MA_OWNED);
+	mpte = pmap_lookup_pt_page(pmap, va);
+	if (mpte == NULL)
+		panic("pmap_remove_kernel_pde: Missing pt page.");
+
+	pmap_remove_pt_page(pmap, mpte);
+	mptepa = VM_PAGE_TO_PHYS(mpte);
+	newpde = mptepa | PG_M | PG_A | PG_RW | PG_V;
+
+	/*
+	 * Initialize the page table page.
+	 */
+	pagezero((void *)PHYS_TO_DMAP(mptepa));
+
+	/*
+	 * Demote the mapping.
+	 */
+	if (workaround_erratum383)
+		pmap_update_pde(pmap, va, pde, newpde);
+	else
+		pde_store(pde, newpde);
+
+	/*
+	 * Invalidate a stale recursive mapping of the page table page.
+	 */
+	pmap_invalidate_page(pmap, (vm_offset_t)vtopte(va));
+}
+
+/*
  * pmap_remove_pde: do the things to unmap a superpage in a process
  */
 static int
@@ -2837,8 +2875,7 @@ pmap_remove_pde(pmap_t pmap, pd_entry_t *pdq, vm_offset_t sva,
 		}
 	}
 	if (pmap == kernel_pmap) {
-		if (!pmap_demote_pde_locked(pmap, pdq, sva, lockp))
-			panic("pmap_remove_pde: failed demotion");
+		pmap_remove_kernel_pde(pmap, pdq, sva);
 	} else {
 		mpte = pmap_lookup_pt_page(pmap, sva);
 		if (mpte != NULL) {
diff --git a/sys/i386/i386/pmap.c b/sys/i386/i386/pmap.c
index 9556458..77b0235 100644
--- a/sys/i386/i386/pmap.c
+++ b/sys/i386/i386/pmap.c
@@ -2773,6 +2773,44 @@ pmap_demote_pde(pmap_t pmap, pd_entry_t *pde, vm_offset_t va)
 }
 
 /*
+ * Removes a 2- or 4MB page mapping from the kernel pmap.
+ */
+static void
+pmap_remove_kernel_pde(pmap_t pmap, pd_entry_t *pde, vm_offset_t va)
+{
+	pd_entry_t newpde;
+	vm_paddr_t mptepa;
+	vm_page_t mpte;
+
+	PMAP_LOCK_ASSERT(pmap, MA_OWNED);
+	mpte = pmap_lookup_pt_page(pmap, va);
+	if (mpte == NULL)
+		panic("pmap_remove_kernel_pde: Missing pt page.");
+
+	pmap_remove_pt_page(pmap, mpte);
+	mptepa = VM_PAGE_TO_PHYS(mpte);
+	newpde = mptepa | PG_M | PG_A | PG_RW | PG_V;
+
+	/*
+	 * Initialize the page table page.
+	 */
+	pagezero((void *)&KPTmap[i386_btop(trunc_4mpage(va))]);
+
+	/*
+	 * Remove the mapping.
+	 */
+	if (workaround_erratum383)
+		pmap_update_pde(pmap, va, pde, newpde);
+	else 
+		pmap_kenter_pde(va, newpde);
+
+	/*
+	 * Invalidate the recursive mapping of the page table page.
+	 */
+	pmap_invalidate_page(pmap, (vm_offset_t)vtopte(va));
+}
+
+/*
  * pmap_remove_pde: do the things to unmap a superpage in a process
  */
 static void
@@ -2814,8 +2852,7 @@ pmap_remove_pde(pmap_t pmap, pd_entry_t *pdq, vm_offset_t sva,
 		}
 	}
 	if (pmap == kernel_pmap) {
-		if (!pmap_demote_pde(pmap, pdq, sva))
-			panic("pmap_remove_pde: failed demotion");
+		pmap_remove_kernel_pde(pmap, pdq, sva);
 	} else {
 		mpte = pmap_lookup_pt_page(pmap, sva);
 		if (mpte != NULL) {
-- 
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