Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759732AbcCDSRO (ORCPT ); Fri, 4 Mar 2016 13:17:14 -0500 Received: from mga09.intel.com ([134.134.136.24]:63681 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759296AbcCDSRK (ORCPT ); Fri, 4 Mar 2016 13:17:10 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.22,536,1449561600"; d="scan'208";a="929778778" From: Yu-cheng Yu To: x86@kernel.org, "H. Peter Anvin" , Thomas Gleixner , Ingo Molnar , linux-kernel@vger.kernel.org Cc: Dave Hansen , Andy Lutomirski , Borislav Petkov , Sai Praneeth Prakhya , "Ravi V. Shankar" , Fenghua Yu , Yu-cheng Yu Subject: [PATCH v4 03/10] x86/xsaves: Keep init_fpstate.xsave.header.xfeatures as zero for init optimization Date: Fri, 4 Mar 2016 10:12:32 -0800 Message-Id: <8ffe13199dbe5f1326f3a0779e82022e83261165.1457038929.git.yu-cheng.yu@intel.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: References: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1292 Lines: 36 Keep init_fpstate.xsave.header.xfeatures as zero for init optimization. This is important for init optimization that is implemented in processor. If a bit corresponding to an xstate in xstate_bv is 0, it means the xstate is in init status and will not be read from memory to the processor during XRSTOR/XRSTORS instruction. This largely impacts context switch performance. Signed-off-by: Fenghua Yu Signed-off-by: Yu-cheng Yu Reviewed-by: Dave Hansen --- arch/x86/kernel/fpu/xstate.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c index b8d6d98..25e11a1 100644 --- a/arch/x86/kernel/fpu/xstate.c +++ b/arch/x86/kernel/fpu/xstate.c @@ -311,13 +311,11 @@ static void __init setup_init_fpu_buf(void) setup_xstate_features(); print_xstate_features(); - if (cpu_has_xsaves) { + if (cpu_has_xsaves) init_fpstate.xsave.header.xcomp_bv = (u64)1 << 63 | xfeatures_mask; - init_fpstate.xsave.header.xfeatures = xfeatures_mask; - } /* - * Init all the features state with header_bv being 0x0 + * Init all the features state with header.xfeatures being 0x0 */ copy_kernel_to_xregs_booting(&init_fpstate.xsave); -- 1.9.1