Commit-ID: 429ed86b5c99b388543f6f7f6983b1230326f2bb Gitweb: http://git.kernel.org/tip/429ed86b5c99b388543f6f7f6983b1230326f2bb Author: Mikulas Patocka <[email protected]> AuthorDate: Tue, 11 Jul 2017 07:44:05 -0400 Committer: Ingo Molnar <[email protected]> CommitDate: Wed, 12 Jul 2017 10:42:32 +0200
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 <[email protected]> Cc: Andy Lutomirski <[email protected]> Cc: Borislav Petkov <[email protected]> Cc: Brian Gerst <[email protected]> Cc: Denys Vlasenko <[email protected]> Cc: H. Peter Anvin <[email protected]> Cc: Josh Poimboeuf <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Thomas Gleixner <[email protected]> Link: http://lkml.kernel.org/r/alpine.lrh.2.02.1707110737530.8...@file01.intranet.prod.int.rdu2.redhat.com Signed-off-by: Ingo Molnar <[email protected]> --- 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 bb5abe8..3b9e220 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();
