svn commit: r253949 - in head/sys: amd64/amd64 i386/i386

[Jeff Roberson]

Author: jeff
Date: Mon Aug  5 00:28:03 2013
New Revision: 253949
URL: http://svnweb.freebsd.org/changeset/base/253949

Log:
   - 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

Modified:
  head/sys/amd64/amd64/pmap.c
  head/sys/i386/i386/pmap.c

Modified: head/sys/amd64/amd64/pmap.c
==============================================================================
--- head/sys/amd64/amd64/pmap.c	Sun Aug  4 23:45:04 2013	(r253948)
+++ head/sys/amd64/amd64/pmap.c	Mon Aug  5 00:28:03 2013	(r253949)
@@ -2795,6 +2795,44 @@ pmap_demote_pde_locked(pmap_t pmap, pd_e
 }
 
 /*
+ * 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 
 		}
 	}
 	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) {

Modified: head/sys/i386/i386/pmap.c
==============================================================================
--- head/sys/i386/i386/pmap.c	Sun Aug  4 23:45:04 2013	(r253948)
+++ head/sys/i386/i386/pmap.c	Mon Aug  5 00:28:03 2013	(r253949)
@@ -2773,6 +2773,44 @@ pmap_demote_pde(pmap_t pmap, pd_entry_t 
 }
 
 /*
+ * 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 
 		}
 	}
 	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) {