[PATCH] linux/i386: enhance dump_fault_path() in the highpte case

[PATCH] linux/i386: enhance dump_fault_path() in the highpte case

[Jan Beulich]

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