7 files changed, 39 insertions, 16 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 4287696f18d..94ce0d20253 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -695,8 +695,15 @@ and is between 256 and 4096 characters. It is defined in the file
         idebus=         [HW] (E)IDE subsystem - VLB/PCI bus speed
                         See Documentation/ide.txt.
 
-        idle=           [HW]
-                        Format: idle=poll or idle=halt
+        idle=           [X86]
+                        Format: idle=poll or idle=mwait
+                        Poll forces a polling idle loop that can slightly improves the performance
+                        of waking up a idle CPU, but will use a lot of power and make the system
+                        run hot. Not recommended.
+                        idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
+                        to not use it because it doesn't save as much power as a normal idle
+                        loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
+                        as idle=poll.
 
         ignore_loglevel [KNL]
                         Ignore loglevel setting - this will print /all/
diff --git a/arch/i386/kernel/cpu/amd.c b/arch/i386/kernel/cpu/amd.c
index 2d47db48297..197cda62caa 100644
--- a/arch/i386/kernel/cpu/amd.c
+++ b/arch/i386/kernel/cpu/amd.c
@@ -53,6 +53,8 @@ static __cpuinit int amd_apic_timer_broken(void)
         return 0;
 }
 
+int force_mwait __cpuinitdata;
+
 static void __cpuinit init_amd(struct cpuinfo_x86 *c)
 {
         u32 l, h;
@@ -275,6 +277,9 @@ static void __cpuinit init_amd(struct cpuinfo_x86 *c)
 
         if (amd_apic_timer_broken())
                 set_bit(X86_FEATURE_LAPIC_TIMER_BROKEN, c->x86_capability);
+
+        if (c->x86 == 0x10 && !force_mwait)
+                clear_bit(X86_FEATURE_MWAIT, c->x86_capability);
 }
 
 static unsigned int __cpuinit amd_size_cache(struct cpuinfo_x86 * c, unsigned int size)
diff --git a/arch/i386/kernel/process.c b/arch/i386/kernel/process.c
index 393a67d5d94..7e8e129b3d7 100644
--- a/arch/i386/kernel/process.c
+++ b/arch/i386/kernel/process.c
@@ -272,25 +272,24 @@ void __devinit select_idle_routine(const struct cpuinfo_x86 *c)
         }
 }
 
-static int __init idle_setup (char *str)
+static int __init idle_setup(char *str)
 {
-        if (!strncmp(str, "poll", 4)) {
+        if (!strcmp(str, "poll")) {
                 printk("using polling idle threads.\n");
                 pm_idle = poll_idle;
 #ifdef CONFIG_X86_SMP
                 if (smp_num_siblings > 1)
                         printk("WARNING: polling idle and HT enabled, performance may degrade.\n");
 #endif
-        } else if (!strncmp(str, "halt", 4)) {
-                printk("using halt in idle threads.\n");
-                pm_idle = default_idle;
-        }
+        } else if (!strcmp(str, "mwait"))
+                force_mwait = 1;
+        else
+                return -1;
 
         boot_option_idle_override = 1;
-        return 1;
+        return 0;
 }
-
-__setup("idle=", idle_setup);
+early_param("idle", idle_setup);
 
 void show_regs(struct pt_regs * regs)
 {
diff --git a/arch/x86_64/kernel/process.c b/arch/x86_64/kernel/process.c
index d8d5ccc245c..4f21765078b 100644
--- a/arch/x86_64/kernel/process.c
+++ b/arch/x86_64/kernel/process.c
@@ -288,16 +288,18 @@ void __cpuinit select_idle_routine(const struct cpuinfo_x86 *c)
 
 static int __init idle_setup (char *str)
 {
-        if (!strncmp(str, "poll", 4)) {
+        if (!strcmp(str, "poll")) {
                 printk("using polling idle threads.\n");
                 pm_idle = poll_idle;
-        }
+        } else if (!strcmp(str, "mwait"))
+                force_mwait = 1;
+        else
+                return -1;
 
         boot_option_idle_override = 1;
-        return 1;
+        return 0;
 }
-
-__setup("idle=", idle_setup);
+early_param("idle", idle_setup);
 
 /* Prints also some state that isn't saved in the pt_regs */ 
 void __show_regs(struct pt_regs * regs)
diff --git a/arch/x86_64/kernel/setup.c b/arch/x86_64/kernel/setup.c
index 0a1d539149d..db30b5bcef6 100644
--- a/arch/x86_64/kernel/setup.c
+++ b/arch/x86_64/kernel/setup.c
@@ -79,6 +79,8 @@ int bootloader_type;
 
 unsigned long saved_video_mode;
 
+int force_mwait __cpuinitdata;
+
 /* 
  * Early DMI memory
  */
@@ -604,6 +606,10 @@ static void __cpuinit init_amd(struct cpuinfo_x86 *c)
 
         /* RDTSC can be speculated around */
         clear_bit(X86_FEATURE_SYNC_RDTSC, &c->x86_capability);
+
+        /* Family 10 doesn't support C states in MWAIT so don't use it */
+        if (c->x86 == 0x10 && !force_mwait)
+                clear_bit(X86_FEATURE_MWAIT, &c->x86_capability);
 }
 
 static void __cpuinit detect_ht(struct cpuinfo_x86 *c)
diff --git a/include/asm-i386/processor.h b/include/asm-i386/processor.h
index 9d895cc2f31..882d3f8fbba 100644
--- a/include/asm-i386/processor.h
+++ b/include/asm-i386/processor.h
@@ -779,4 +779,6 @@ extern int sysenter_setup(void);
 extern void cpu_set_gdt(int);
 extern void cpu_init(void);
 
+extern int force_mwait;
+
 #endif /* __ASM_I386_PROCESSOR_H */
diff --git a/include/asm-x86_64/proto.h b/include/asm-x86_64/proto.h
index 3f8f285138d..98063bcb3b3 100644
--- a/include/asm-x86_64/proto.h
+++ b/include/asm-x86_64/proto.h
@@ -119,6 +119,8 @@ extern int gsi_irq_sharing(int gsi);
 
 extern void smp_local_timer_interrupt(void);
 
+extern int force_mwait;
+
 long do_arch_prctl(struct task_struct *task, int code, unsigned long addr);
 
 void i8254_timer_resume(void);