Xen devel - Jan 2007 - [PATCH] linux/i386: enhance dump_fault_path() in the highpte case

As long as the pte page isn''t really located in highmem, there is no
reason to
not access it, in order to print the complete page table hierarchy.
A functionally similar patch will go to lkml for native Linux.

Signed-off-by: Jan Beulich <jbeulich@novell.com>

Index: sle10-sp1-2007-01-12/arch/i386/mm/fault-xen.c
==================================================================---
sle10-sp1-2007-01-12.orig/arch/i386/mm/fault-xen.c	2007-01-12 09:38:21.000000000
+0100
+++ sle10-sp1-2007-01-12/arch/i386/mm/fault-xen.c	2007-01-15 17:50:33.000000000
+0100
@@ -232,9 +232,12 @@ static void dump_fault_path(unsigned lon
 		p += (address >> 21) * 2;
 		printk(KERN_ALERT "%08lx -> *pme = %08lx:%08lx\n", 
 		       page, p[1], p[0]);
-#ifndef CONFIG_HIGHPTE
+		mfn  = (p[0] >> PAGE_SHIFT) | (p[1] << 20);
+#ifdef CONFIG_HIGHPTE
+		if (mfn_to_pfn(mfn) >= highstart_pfn)
+			return;
+#endif
 		if (p[0] & 1) {
-			mfn  = (p[0] >> PAGE_SHIFT) | (p[1] << 20);
 			page = mfn_to_pfn(mfn) << PAGE_SHIFT; 
 			p  = (unsigned long *) __va(page);
 			address &= 0x001fffff;
@@ -242,7 +245,6 @@ static void dump_fault_path(unsigned lon
 			printk(KERN_ALERT "%08lx -> *pte = %08lx:%08lx\n",
 			       page, p[1], p[0]);
 		}
-#endif
 	}
 }
 #else
@@ -254,13 +256,16 @@ static void dump_fault_path(unsigned lon
 	page = ((unsigned long *) __va(page))[address >> 22];
 	printk(KERN_ALERT "*pde = ma %08lx pa %08lx\n", page,
 	       machine_to_phys(page));
+#ifdef CONFIG_HIGHPTE
 	/*
 	 * We must not directly access the pte in the highpte
-	 * case, the page table might be allocated in highmem.
+	 * case if the page table is located in highmem.
 	 * And lets rather not kmap-atomic the pte, just in case
 	 * it''s allocated already.
 	 */
-#ifndef CONFIG_HIGHPTE
+	if ((page >> PAGE_SHIFT) >= highstart_pfn)
+		return;
+#endif
 	if (page & 1) {
 		page &= PAGE_MASK;
 		address &= 0x003ff000;
@@ -269,7 +274,6 @@ static void dump_fault_path(unsigned lon
 		printk(KERN_ALERT "*pte = ma %08lx pa %08lx\n", page,
 		       machine_to_phys(page));
 	}
-#endif
 }
 #endif
 


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