[PATCH] kexec: x86: local apic fix

From: "Maciej W. Rozycki" <macro@linux-mips.org>

Fix a kexec problem whcih causes local APIC detection failure.

The problem is detect_init_APIC() is called early, before the command line
have been processed.  Therefore "lapic" (and "nolapic") have not been seen,
yet.
Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
Signed-off-by: Eric Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/i386/kernel/apic.c

@@ -40,6 +40,11 @@
 
 #include "io_ports.h"
 
+/*
+ * Knob to control our willingness to enable the local APIC.
+ */
+int enable_local_apic __initdata = 0; /* -1=force-disable, +1=force-enable */
+
 /*
  * Debug level
  */
@@ -666,26 +671,6 @@ static void apic_pm_activate(void) { }
  * Original code written by Keir Fraser.
  */
 
-/*
- * Knob to control our willingness to enable the local APIC.
- */
-int enable_local_apic __initdata = 0; /* -1=force-disable, +1=force-enable */
-
-static int __init lapic_disable(char *str)
-{
-	enable_local_apic = -1;
-	clear_bit(X86_FEATURE_APIC, boot_cpu_data.x86_capability);
-	return 0;
-}
-__setup("nolapic", lapic_disable);
-
-static int __init lapic_enable(char *str)
-{
-	enable_local_apic = 1;
-	return 0;
-}
-__setup("lapic", lapic_enable);
-
 static int __init apic_set_verbosity(char *str)
 {
 	if (strcmp("debug", str) == 0)

arch/i386/kernel/setup.c

@@ -44,6 +44,7 @@
 #include <linux/edd.h>
 #include <linux/nodemask.h>
 #include <video/edid.h>
+#include <asm/apic.h>
 #include <asm/e820.h>
 #include <asm/mpspec.h>
 #include <asm/setup.h>
@@ -835,6 +836,16 @@ static void __init parse_cmdline_early (char ** cmdline_p)
 #endif /* CONFIG_X86_LOCAL_APIC */
 #endif /* CONFIG_ACPI_BOOT */
 
+#ifdef CONFIG_X86_LOCAL_APIC
+		/* enable local APIC */
+		else if (!memcmp(from, "lapic", 5))
+			lapic_enable();
+
+		/* disable local APIC */
+		else if (!memcmp(from, "nolapic", 6))
+			lapic_disable();
+#endif /* CONFIG_X86_LOCAL_APIC */
+
 		/*
 		 * highmem=size forces highmem to be exactly 'size' bytes.
 		 * This works even on boxes that have no highmem otherwise.

include/asm-i386/apic.h

@@ -5,6 +5,7 @@
 #include <linux/pm.h>
 #include <asm/fixmap.h>
 #include <asm/apicdef.h>
+#include <asm/processor.h>
 #include <asm/system.h>
 
 #define Dprintk(x...)
@@ -16,8 +17,20 @@
 #define APIC_VERBOSE 1
 #define APIC_DEBUG   2
 
+extern int enable_local_apic;
 extern int apic_verbosity;
 
+static inline void lapic_disable(void)
+{
+	enable_local_apic = -1;
+	clear_bit(X86_FEATURE_APIC, boot_cpu_data.x86_capability);
+}
+
+static inline void lapic_enable(void)
+{
+	enable_local_apic = 1;
+}
+
 /*
  * Define the default level of output to be very little
  * This can be turned up by using apic=verbose for more