Commit-ID: 429ed86b5c99b388543f6f7f6983b1230326f2bb Gitweb: http://git.kernel.org/tip/429ed86b5c99b388543f6f7f6983b1230326f2bb Author: Mikulas Patocka <mpato...@redhat.com> AuthorDate: Tue, 11 Jul 2017 07:44:05 -0400 Committer: Ingo Molnar <mi...@kernel.org> 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 <mpato...@redhat.com> Cc: Andy Lutomirski <l...@kernel.org> Cc: Borislav Petkov <b...@alien8.de> Cc: Brian Gerst <brge...@gmail.com> Cc: Denys Vlasenko <dvlas...@redhat.com> Cc: H. Peter Anvin <h...@zytor.com> Cc: Josh Poimboeuf <jpoim...@redhat.com> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Thomas Gleixner <t...@linutronix.de> Link: http://lkml.kernel.org/r/alpine.lrh.2.02.1707110737530.8...@file01.intranet.prod.int.rdu2.redhat.com Signed-off-by: Ingo Molnar <mi...@kernel.org> --- 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();
