Messages in this thread Patch in this message | | | Date | Sun, 16 Jul 2017 02:14:17 -0700 | From | tip-bot for Mikulas Patocka <> | Subject | [tip:x86/urgent] x86/cpu: Use indirect call to measure performance in init_amd_k6() |
| |
Commit-ID: 5f8a16156aa1b2d0223eaee9dacdfb9bc096f610 Gitweb: http://git.kernel.org/tip/5f8a16156aa1b2d0223eaee9dacdfb9bc096f610 Author: Mikulas Patocka <mpatocka@redhat.com> AuthorDate: Tue, 11 Jul 2017 07:44:05 -0400 Committer: Ingo Molnar <mingo@kernel.org> CommitDate: Sun, 16 Jul 2017 11:05:04 +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 <mpatocka@redhat.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/alpine.LRH.2.02.1707110737530.8746@file01.intranet.prod.int.rdu2.redhat.com Signed-off-by: Ingo Molnar <mingo@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();
| |