[Lguest] lguest: mapping switcher would thwack fixmap

[Paul Bolle]

0) Loading the lg module (on v3.8.5) triggers an error:
    lguest: mapping switcher would thwack fixmap

1) I'm not enitrely sure what the fixmap is, but dmesg tells me:
    kernel: [    0.000000]     fixmap  : 0xffa95000 - 0xfffff000   (5544 kB)

2) I managed to load the lg modules after rebuilding it with this path
(from the see-what-happens-if-I-hit-it department) applied:
diff -up linux/arch/x86/include/asm/lguest.h.fixmap linux/arch/x86/include/asm/lguest.h
--- linux/arch/x86/include/asm/lguest.h.fixmap  2013-02-19 00:58:34.000000000 +0100
+++ linux/arch/x86/include/asm/lguest.h 2013-03-31 23:54:08.699405679 +0200
@@ -21,7 +21,7 @@
 #ifdef CONFIG_X86_PAE
 #define SWITCHER_ADDR 0xFFE00000
 #else
-#define SWITCHER_ADDR 0xFFC00000
+#define SWITCHER_ADDR 0xFFA00000
 #endif

 /* Found in switcher.S */

3) But if I then try to actually run the lguest tool, that machine
reboots. I have no clue why. (An uneducated guess would be because of
"triple fault".)

4) Any idea what could be going on? And any suggestion to fix this?


Paul Bolle