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

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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>
This commit is contained in:
Christoph Lameter 2011-03-12 12:50:10 +01:00 committed by Tejun Heo
parent 89078d572e
commit 349c004e3d
5 changed files with 41 additions and 9 deletions
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13
arch/x86/include/asm/cpufeature.h
View File

@ -207,8 +207,7 @@ extern const char * const x86_power_flags[32];
#define test_cpu_cap(c, bit) \
test_bit(bit, (unsigned long *)((c)->x86_capability))
#define cpu_has(c, bit) \
(__builtin_constant_p(bit) && \
#define REQUIRED_MASK_BIT_SET(bit) \
( (((bit)>>5)==0 && (1UL<<((bit)&31) & REQUIRED_MASK0)) || \
(((bit)>>5)==1 && (1UL<<((bit)&31) & REQUIRED_MASK1)) || \
(((bit)>>5)==2 && (1UL<<((bit)&31) & REQUIRED_MASK2)) || \
@ -218,10 +217,16 @@ extern const char * const x86_power_flags[32];
(((bit)>>5)==6 && (1UL<<((bit)&31) & REQUIRED_MASK6)) || \
(((bit)>>5)==7 && (1UL<<((bit)&31) & REQUIRED_MASK7)) || \
(((bit)>>5)==8 && (1UL<<((bit)&31) & REQUIRED_MASK8)) || \
(((bit)>>5)==9 && (1UL<<((bit)&31) & REQUIRED_MASK9)) ) \
? 1 : \
(((bit)>>5)==9 && (1UL<<((bit)&31) & REQUIRED_MASK9)) )
#define cpu_has(c, bit) \
(__builtin_constant_p(bit) && REQUIRED_MASK_BIT_SET(bit) ? 1 : \
test_cpu_cap(c, bit))
#define this_cpu_has(bit) \
(__builtin_constant_p(bit) && REQUIRED_MASK_BIT_SET(bit) ? 1 : \
x86_this_cpu_test_bit(bit, (unsigned long *)&cpu_info.x86_capability))
#define boot_cpu_has(bit) cpu_has(&boot_cpu_data, bit)
#define set_cpu_cap(c, bit) set_bit(bit, (unsigned long *)((c)->x86_capability))

27
arch/x86/include/asm/percpu.h
View File

@ -542,6 +542,33 @@ do { \
old__; \
})
static __always_inline int x86_this_cpu_constant_test_bit(unsigned int nr,
const unsigned long __percpu *addr)
{
unsigned long __percpu *a = (unsigned long *)addr + nr / BITS_PER_LONG;
return ((1UL << (nr % BITS_PER_LONG)) & percpu_read(*a)) != 0;
}
static inline int x86_this_cpu_variable_test_bit(int nr,
const unsigned long __percpu *addr)
{
int oldbit;
asm volatile("bt "__percpu_arg(2)",%1\n\t"
"sbb %0,%0"
: "=r" (oldbit)
: "m" (*(unsigned long *)addr), "Ir" (nr));
return oldbit;
}
#define x86_this_cpu_test_bit(nr, addr) \
(__builtin_constant_p((nr)) \
? x86_this_cpu_constant_test_bit((nr), (addr)) \
: x86_this_cpu_variable_test_bit((nr), (addr)))
#include <asm-generic/percpu.h>
/* We can use this directly for local CPU (faster). */

2
arch/x86/kernel/apic/apic.c
View File

@ -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;

4
arch/x86/kernel/process.c
View File

@ -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);

4
arch/x86/kernel/smpboot.c
View File

@ -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;