From c8e5910edf8bbe2e5c6c35a4ef2a578cc7893b25 Mon Sep 17 00:00:00 2001 From: Robert Richter Date: Sat, 16 Apr 2011 02:27:55 +0200 Subject: [PATCH] perf, x86: Use ALTERNATIVE() to check for X86_FEATURE_PERFCTR_CORE Using ALTERNATIVE() when checking for X86_FEATURE_PERFCTR_CORE avoids an extra pointer chase and data cache hit. Signed-off-by: Robert Richter Signed-off-by: Peter Zijlstra Link: http://lkml.kernel.org/r/1302913676-14352-4-git-send-email-robert.richter@amd.com Signed-off-by: Ingo Molnar --- arch/x86/kernel/cpu/perf_event.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-) diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c index eed3673a8656..224a84f7080c 100644 --- a/arch/x86/kernel/cpu/perf_event.c +++ b/arch/x86/kernel/cpu/perf_event.c @@ -31,6 +31,7 @@ #include #include #include +#include #if 0 #undef wrmsrl @@ -363,12 +364,18 @@ again: return new_raw_count; } -/* using X86_FEATURE_PERFCTR_CORE to later implement ALTERNATIVE() here */ static inline int x86_pmu_addr_offset(int index) { - if (boot_cpu_has(X86_FEATURE_PERFCTR_CORE)) - return index << 1; - return index; + int offset; + + /* offset = X86_FEATURE_PERFCTR_CORE ? index << 1 : index */ + alternative_io(ASM_NOP2, + "shll $1, %%eax", + X86_FEATURE_PERFCTR_CORE, + "=a" (offset), + "a" (index)); + + return offset; } static inline unsigned int x86_pmu_config_addr(int index) -- 2.20.1