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

To: <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: [Xen-devel] [PATCH] linux/i386: enhance dump_fault_path() in the highpte case
From: "Jan Beulich" <jbeulich@xxxxxxxxxx>
Date: Tue, 16 Jan 2007 12:59:42 +0000
Delivery-date: Tue, 16 Jan 2007 04:57:36 -0800
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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@xxxxxxxxxx>

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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