[PATCH] x86: sutomatically enable bigsmp when we have more than 8 CPUs

i386 generic subarchitecture requires explicit dmi strings or command line
to enable bigsmp mode.  The patch below removes that restriction, and uses
bigsmp as soon as it finds more than 8 logical CPUs, Intel processors and
xAPIC support.

Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 20 insertions, 0 deletions

diff --git a/arch/i386/mach-generic/probe.c b/arch/i386/mach-generic/probe.c
index 5497c65a8790..cea5b3ce4b57 100644
--- a/arch/i386/mach-generic/probe.c
+++ b/arch/i386/mach-generic/probe.c
@@ -30,6 +30,25 @@ struct genapic *apic_probe[] __initdata = {
         NULL,
 };
 
+static int cmdline_apic;
+
+void __init generic_bigsmp_probe(void)
+{
+        /*
+         * This routine is used to switch to bigsmp mode when
+         * - There is no apic= option specified by the user
+         * - generic_apic_probe() has choosen apic_default as the sub_arch
+         * - we find more than 8 CPUs in acpi LAPIC listing with xAPIC support
+         */
+
+        if (!cmdline_apic && genapic == &apic_default)
+                if (apic_bigsmp.probe()) {
+                        genapic = &apic_bigsmp;
+                        printk(KERN_INFO "Overriding APIC driver with %s\n",
+                               genapic->name);
+                }
+}
+
 void __init generic_apic_probe(char *command_line) 
 { 
         char *s;
@@ -52,6 +71,7 @@ void __init generic_apic_probe(char *command_line)
                 if (!changed)
                         printk(KERN_ERR "Unknown genapic `%s' specified.\n", s);
                 *p = old;
+                cmdline_apic = changed;
         } 
         for (i = 0; !changed && apic_probe[i]; i++) { 
                 if (apic_probe[i]->probe()) {