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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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4
arch/x86/kernel/smpboot.c
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@@ -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;