From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753984Ab3FIKIH (ORCPT ); Sun, 9 Jun 2013 06:08:07 -0400 Received: from mail.skyhub.de ([78.46.96.112]:47463 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753057Ab3FIKHi (ORCPT ); Sun, 9 Jun 2013 06:07:38 -0400 From: Borislav Petkov To: "H. Peter Anvin" Cc: X86 ML , LKML , Borislav Petkov Subject: [PATCH 5/5] x86, FPU: Use static_cpu_has_safe before alternatives Date: Sun, 9 Jun 2013 12:07:34 +0200 Message-Id: <1370772454-6106-6-git-send-email-bp@alien8.de> X-Mailer: git-send-email 1.8.3 In-Reply-To: <1370772454-6106-1-git-send-email-bp@alien8.de> References: <1370772454-6106-1-git-send-email-bp@alien8.de> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Borislav Petkov The call stack below shows how this happens: basically eager_fpu_init() calls __thread_fpu_begin(current) which then does if (!use_eager_fpu()), which, in turn, uses static_cpu_has. And we're executing before alternatives so static_cpu_has doesn't work there yet. Use the safe variant in this path which becomes optimal after alternatives have run. WARNING: at arch/x86/kernel/cpu/common.c:1368 warn_pre_alternatives+0x1e/0x20() You're using static_cpu_has before alternatives have run! Modules linked in: Pid: 0, comm: swapper Not tainted 3.9.0-rc8+ #1 Call Trace: warn_slowpath_common warn_slowpath_fmt ? fpu_finit warn_pre_alternatives eager_fpu_init fpu_init cpu_init trap_init start_kernel ? repair_env_string x86_64_start_reservations x86_64_start_kernel Signed-off-by: Borislav Petkov --- arch/x86/include/asm/fpu-internal.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/include/asm/fpu-internal.h b/arch/x86/include/asm/fpu-internal.h index e25cc33ec54d..b36f31b18664 100644 --- a/arch/x86/include/asm/fpu-internal.h +++ b/arch/x86/include/asm/fpu-internal.h @@ -345,7 +345,7 @@ static inline void __thread_fpu_end(struct task_struct *tsk) static inline void __thread_fpu_begin(struct task_struct *tsk) { - if (!use_eager_fpu()) + if (!static_cpu_has_safe(X86_FEATURE_EAGER_FPU)) clts(); __thread_set_has_fpu(tsk); } -- 1.8.3