Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755981Ab3HPWhi (ORCPT ); Fri, 16 Aug 2013 18:37:38 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:51449 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754727Ab3HPWhe (ORCPT ); Fri, 16 Aug 2013 18:37:34 -0400 From: Kamal Mostafa To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: "H. Peter Anvin" , Kamal Mostafa Subject: [PATCH 085/133] x86, fpu: correct the asm constraints for fxsave, unbreak mxcsr.daz Date: Fri, 16 Aug 2013 15:33:47 -0700 Message-Id: <1376692475-28413-86-git-send-email-kamal@canonical.com> X-Mailer: git-send-email 1.8.1.2 In-Reply-To: <1376692475-28413-1-git-send-email-kamal@canonical.com> References: <1376692475-28413-1-git-send-email-kamal@canonical.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Extended-Stable: 3.8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1693 Lines: 53 3.8.13.7 -stable review patch. If anyone has any objections, please let me know. ------------------ From: "H.J. Lu" commit eaa5a990191d204ba0f9d35dbe5505ec2cdd1460 upstream. GCC will optimize mxcsr_feature_mask_init in arch/x86/kernel/i387.c: memset(&fx_scratch, 0, sizeof(struct i387_fxsave_struct)); asm volatile("fxsave %0" : : "m" (fx_scratch)); mask = fx_scratch.mxcsr_mask; if (mask == 0) mask = 0x0000ffbf; to memset(&fx_scratch, 0, sizeof(struct i387_fxsave_struct)); asm volatile("fxsave %0" : : "m" (fx_scratch)); mask = 0x0000ffbf; since asm statement doesn’t say it will update fx_scratch. As the result, the DAZ bit will be cleared. This patch fixes it. This bug dates back to at least kernel 2.6.12. Signed-off-by: H. Peter Anvin Signed-off-by: Kamal Mostafa --- arch/x86/kernel/i387.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c index cb33909..f7ea30d 100644 --- a/arch/x86/kernel/i387.c +++ b/arch/x86/kernel/i387.c @@ -116,7 +116,7 @@ static void __cpuinit mxcsr_feature_mask_init(void) if (cpu_has_fxsr) { memset(&fx_scratch, 0, sizeof(struct i387_fxsave_struct)); - asm volatile("fxsave %0" : : "m" (fx_scratch)); + asm volatile("fxsave %0" : "+m" (fx_scratch)); mask = fx_scratch.mxcsr_mask; if (mask == 0) mask = 0x0000ffbf; -- 1.8.1.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/