[PATCH] x86: Apm is on cpu zero only

APM BIOS code has a protective wrapper that runs it only on CPU zero.  Thus,
no need to set APM BIOS segments in the GDT for other CPUs.

Signed-off-by: Zachary Amsden <zach@vmware.com>
Acked-by: "Seth, Rohit" <rohit.seth@intel.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 11 insertions, 12 deletions

diff --git a/arch/i386/kernel/apm.c b/arch/i386/kernel/apm.c
index 45199bb6455b..d0b488056cc4 100644
--- a/arch/i386/kernel/apm.c
+++ b/arch/i386/kernel/apm.c
@@ -2222,8 +2222,8 @@ static struct dmi_system_id __initdata apm_dmi_table[] = {
 static int __init apm_init(void)
 {
         struct proc_dir_entry *apm_proc;
+        struct desc_struct *gdt;
         int ret;
-        int i;
 
         dmi_check_system(apm_dmi_table);
 
@@ -2314,18 +2314,17 @@ static int __init apm_init(void)
          * not restrict themselves to their claimed limit.  When this happens,
          * they will cause a segmentation violation in the kernel at boot time.
          * Most BIOS's, however, will respect a 64k limit, so we use that.
+         *
+         * Note we only set APM segments on CPU zero, since we pin the APM
+         * code to that CPU.
          */
-        for (i = 0; i < NR_CPUS; i++) {
-                struct desc_struct *gdt = get_cpu_gdt_table(i);
-                if (!gdt)
-                        continue;
-                set_base(gdt[APM_CS >> 3],
-                         __va((unsigned long)apm_info.bios.cseg << 4));
-                set_base(gdt[APM_CS_16 >> 3],
-                         __va((unsigned long)apm_info.bios.cseg_16 << 4));
-                set_base(gdt[APM_DS >> 3],
-                         __va((unsigned long)apm_info.bios.dseg << 4));
-        }
+        gdt = get_cpu_gdt_table(0);
+        set_base(gdt[APM_CS >> 3],
+                 __va((unsigned long)apm_info.bios.cseg << 4));
+        set_base(gdt[APM_CS_16 >> 3],
+                 __va((unsigned long)apm_info.bios.cseg_16 << 4));
+        set_base(gdt[APM_DS >> 3],
+                 __va((unsigned long)apm_info.bios.dseg << 4));
 
         apm_proc = create_proc_info_entry("apm", 0, NULL, apm_get_info);
         if (apm_proc)