From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9CEE2C169C4 for ; Thu, 31 Jan 2019 17:45:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6E3B621902 for ; Thu, 31 Jan 2019 17:45:02 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=c-s.fr header.i=@c-s.fr header.b="SDoC3Gfm" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727169AbfAaRpA (ORCPT ); Thu, 31 Jan 2019 12:45:00 -0500 Received: from pegase1.c-s.fr ([93.17.236.30]:65208 "EHLO pegase1.c-s.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726877AbfAaRo4 (ORCPT ); Thu, 31 Jan 2019 12:44:56 -0500 Received: from localhost (mailhub1-int [192.168.12.234]) by localhost (Postfix) with ESMTP id 43r70j4T7wz9vBKq; Thu, 31 Jan 2019 18:44:53 +0100 (CET) Authentication-Results: localhost; dkim=pass reason="1024-bit key; insecure key" header.d=c-s.fr header.i=@c-s.fr header.b=SDoC3Gfm; dkim-adsp=pass; dkim-atps=neutral X-Virus-Scanned: Debian amavisd-new at c-s.fr Received: from pegase1.c-s.fr ([192.168.12.234]) by localhost (pegase1.c-s.fr [192.168.12.234]) (amavisd-new, port 10024) with ESMTP id eKvne8ryPTPS; Thu, 31 Jan 2019 18:44:53 +0100 (CET) Received: from messagerie.si.c-s.fr (messagerie.si.c-s.fr [192.168.25.192]) by pegase1.c-s.fr (Postfix) with ESMTP id 43r70j30tgz9vBKn; Thu, 31 Jan 2019 18:44:53 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=c-s.fr; s=mail; t=1548956693; bh=ugoZ4ISKI/Wbc3x+9e2KTETw23VmyIlLo+gOrAR3JkI=; h=From:Subject:To:Cc:Date:From; b=SDoC3Gfm7FV7wDF3RLUH1e5K9f7/WNELtvyy0QaqUYZ1EZd8/f7JIVcQlrFc20q1U 0wIB9oyitc7HdE6fwM6VHAq5DX/KVsQDmdilrmt9nF7oDQY3QO05SG50EHfOdFhzjm uU/qxhSqh/dnwr9Xq5UxgZy9CRnLQwzs8CECC1XY= Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 18D5D8B83A; Thu, 31 Jan 2019 18:44:55 +0100 (CET) X-Virus-Scanned: amavisd-new at c-s.fr Received: from messagerie.si.c-s.fr ([127.0.0.1]) by localhost (messagerie.si.c-s.fr [127.0.0.1]) (amavisd-new, port 10023) with ESMTP id Qx5-lQXDOIpQ; Thu, 31 Jan 2019 18:44:55 +0100 (CET) Received: from po16846vm.idsi0.si.c-s.fr (unknown [192.168.4.90]) by messagerie.si.c-s.fr (Postfix) with ESMTP id EAEEF8B835; Thu, 31 Jan 2019 18:44:54 +0100 (CET) Received: by po16846vm.idsi0.si.c-s.fr (Postfix, from userid 0) id BA05F72E25; Thu, 31 Jan 2019 17:44:54 +0000 (UTC) Message-Id: <9f9dd859d571e324c7412ed9db9da8cfba678257.1548956511.git.christophe.leroy@c-s.fr> From: Christophe Leroy Subject: [RFC PATCH] powerpc/6xx: Don't set back MSR_RI before reenabling MMU To: Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org Date: Thu, 31 Jan 2019 17:44:54 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org By delaying the setting of MSR_RI, a 1% improvment is optained on null_syscall selftest on an mpc8321. Without this patch: root@vgoippro:~# ./null_syscall 1134.33 ns 378.11 cycles With this patch: root@vgoippro:~# ./null_syscall 1121.85 ns 373.95 cycles The drawback is that a machine check during that period would be unrecoverable, but as only main memory is accessed during that period, it shouldn't be a concern. Signed-off-by: Christophe Leroy --- arch/powerpc/kernel/head_32.S | 2 -- 1 file changed, 2 deletions(-) diff --git a/arch/powerpc/kernel/head_32.S b/arch/powerpc/kernel/head_32.S index 146385b1c2da..ea28a6ab56ec 100644 --- a/arch/powerpc/kernel/head_32.S +++ b/arch/powerpc/kernel/head_32.S @@ -282,8 +282,6 @@ __secondary_hold_acknowledge: stw r1,GPR1(r11); \ stw r1,0(r11); \ tovirt(r1,r11); /* set new kernel sp */ \ - li r10,MSR_KERNEL & ~(MSR_IR|MSR_DR); /* can take exceptions */ \ - MTMSRD(r10); /* (except for mach check in rtas) */ \ stw r0,GPR0(r11); \ lis r10,STACK_FRAME_REGS_MARKER@ha; /* exception frame marker */ \ addi r10,r10,STACK_FRAME_REGS_MARKER@l; \ -- 2.13.3