From 5f8a16156aa1b2d0223eaee9dacdfb9bc096f610 Mon Sep 17 00:00:00 2001 From: Mikulas Patocka Date: Tue, 11 Jul 2017 07:44:05 -0400 Subject: [PATCH] x86/cpu: Use indirect call to measure performance in init_amd_k6() This old piece of code is supposed to measure the performance of indirect calls to determine if the processor is buggy or not, however the compiler optimizer turns it into a direct call. Use the OPTIMIZER_HIDE_VAR() macro to thwart the optimization, so that a real indirect call is generated. Signed-off-by: Mikulas Patocka Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Josh Poimboeuf Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/alpine.LRH.2.02.1707110737530.8746@file01.intranet.prod.int.rdu2.redhat.com Signed-off-by: Ingo Molnar --- arch/x86/kernel/cpu/amd.c | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c index bb5abe8f5fd4..3b9e220621f8 100644 --- a/arch/x86/kernel/cpu/amd.c +++ b/arch/x86/kernel/cpu/amd.c @@ -134,6 +134,7 @@ static void init_amd_k6(struct cpuinfo_x86 *c) n = K6_BUG_LOOP; f_vide = vide; + OPTIMIZER_HIDE_VAR(f_vide); d = rdtsc(); while (n--) f_vide(); -- 2.20.1