From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751393AbcBVTAv (ORCPT ); Mon, 22 Feb 2016 14:00:51 -0500 Received: from mga09.intel.com ([134.134.136.24]:23927 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751403AbcBVTAt (ORCPT ); Mon, 22 Feb 2016 14:00:49 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.22,485,1449561600"; d="scan'208";a="751104598" 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 03/10] x86/xsaves: Keep init_fpstate.xsave.header.xfeatures as zero for init optimization Date: Mon, 22 Feb 2016 10:58:18 -0800 Message-Id: <1456167498-3763-1-git-send-email-yu-cheng.yu@intel.com> X-Mailer: git-send-email 1.9.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c index b8d6d98..daff143 100644 --- a/arch/x86/kernel/fpu/xstate.c +++ b/arch/x86/kernel/fpu/xstate.c @@ -311,10 +311,8 @@ 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 -- 1.9.1