x86: A fast way to check capabilities of the current cpu

Add this_cpu_has() which determines if the current cpu has a certain
ability using a segment prefix and a bit test operation.

For that we need to add bit operations to x86s percpu.h.

Many uses of cpu_has use a pointer passed to a function to determine
the current flags. That is no longer necessary after this patch.

However, this patch only converts the straightforward cases where
cpu_has is used with this_cpu_ptr. The rest is work for later.

-tj: Rolled up patch to add x86_ prefix and use percpu_read() instead
     of percpu_read_stable().

Signed-off-by: Christoph Lameter <cl@linux.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Tejun Heo <tj@kernel.org>

3 files changed, 5 insertions, 5 deletions

diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index fabf01eff771..2bc503bf9e99 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -505,7 +505,7 @@ static void __cpuinit setup_APIC_timer(void)
 {
         struct clock_event_device *levt = &__get_cpu_var(lapic_events);
 
-        if (cpu_has(__this_cpu_ptr(&cpu_info), X86_FEATURE_ARAT)) {
+        if (this_cpu_has(X86_FEATURE_ARAT)) {
                 lapic_clockevent.features &= ~CLOCK_EVT_FEAT_C3STOP;
                 /* Make LAPIC timer preferrable over percpu HPET */
                 lapic_clockevent.rating = 150;
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index d46cbe46b7ab..88a90a977f8e 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -449,7 +449,7 @@ EXPORT_SYMBOL_GPL(cpu_idle_wait);
 void mwait_idle_with_hints(unsigned long ax, unsigned long cx)
 {
         if (!need_resched()) {
-                if (cpu_has(__this_cpu_ptr(&cpu_info), X86_FEATURE_CLFLUSH_MONITOR))
+                if (this_cpu_has(X86_FEATURE_CLFLUSH_MONITOR))
                         clflush((void *)&current_thread_info()->flags);
 
                 __monitor((void *)&current_thread_info()->flags, 0, 0);
@@ -465,7 +465,7 @@ static void mwait_idle(void)
         if (!need_resched()) {
                 trace_power_start(POWER_CSTATE, 1, smp_processor_id());
                 trace_cpu_idle(1, smp_processor_id());
-                if (cpu_has(__this_cpu_ptr(&cpu_info), X86_FEATURE_CLFLUSH_MONITOR))
+                if (this_cpu_has(X86_FEATURE_CLFLUSH_MONITOR))
                         clflush((void *)&current_thread_info()->flags);
 
                 __monitor((void *)&current_thread_info()->flags, 0, 0);
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index c2871d3c71b6..a3c430bdfb60 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -1332,9 +1332,9 @@ static inline void mwait_play_dead(void)
         void *mwait_ptr;
         struct cpuinfo_x86 *c = __this_cpu_ptr(&cpu_info);
 
-        if (!(cpu_has(c, X86_FEATURE_MWAIT) && mwait_usable(c)))
+        if (!this_cpu_has(X86_FEATURE_MWAIT) && mwait_usable(c))
                 return;
-        if (!cpu_has(__this_cpu_ptr(&cpu_info), X86_FEATURE_CLFLSH))
+        if (!this_cpu_has(X86_FEATURE_CLFLSH))
                 return;
         if (__this_cpu_read(cpu_info.cpuid_level) < CPUID_MWAIT_LEAF)
                 return;