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=-6.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,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 4700AC2BA1B for ; Mon, 6 Apr 2020 18:17:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 258532064A for ; Mon, 6 Apr 2020 18:17:06 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=c-s.fr header.i=@c-s.fr header.b="li6ozEVe" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727409AbgDFSQ6 (ORCPT ); Mon, 6 Apr 2020 14:16:58 -0400 Received: from pegase1.c-s.fr ([93.17.236.30]:14396 "EHLO pegase1.c-s.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727162AbgDFSQx (ORCPT ); Mon, 6 Apr 2020 14:16:53 -0400 Received: from localhost (mailhub1-int [192.168.12.234]) by localhost (Postfix) with ESMTP id 48wzJg1WtHz9v0BP; Mon, 6 Apr 2020 20:16:51 +0200 (CEST) Authentication-Results: localhost; dkim=pass reason="1024-bit key; insecure key" header.d=c-s.fr header.i=@c-s.fr header.b=li6ozEVe; 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 x2vqgQMc-n-j; Mon, 6 Apr 2020 20:16:51 +0200 (CEST) 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 48wzJg0VWhz9v0BL; Mon, 6 Apr 2020 20:16:51 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=c-s.fr; s=mail; t=1586197011; bh=m6Oh1yuts4ObrTSh3NAo4HJzDL11EvAmq8RhV9wYZ0A=; h=In-Reply-To:References:From:Subject:To:Cc:Date:From; b=li6ozEVeosEy5FvAn9MK+991oPDvsLU6AtwUENgL/JBp1qy10smsFXTv2AC92QYX1 RATvpWnnVDQVcB+rVHrYIKudA+RnKjz/zUSXfiHE2zTy9G+BtRv1u/LJ21zvVcjCYU OYwu8MW3+wiP9P9KydE69XOBlDEToZ64et4onk1g= Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 0A79B8B784; Mon, 6 Apr 2020 20:16:51 +0200 (CEST) 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 uMEmrDBE1TQV; Mon, 6 Apr 2020 20:16:50 +0200 (CEST) Received: from pc16570vm.idsi0.si.c-s.fr (unknown [192.168.4.90]) by messagerie.si.c-s.fr (Postfix) with ESMTP id A6ED88B775; Mon, 6 Apr 2020 20:16:50 +0200 (CEST) Received: by pc16570vm.idsi0.si.c-s.fr (Postfix, from userid 0) id 7BE7C656E9; Mon, 6 Apr 2020 18:16:50 +0000 (UTC) Message-Id: In-Reply-To: <5aeaa33383e833f6eca30893fbd188b88e019eaa.1586196948.git.christophe.leroy@c-s.fr> References: <5aeaa33383e833f6eca30893fbd188b88e019eaa.1586196948.git.christophe.leroy@c-s.fr> From: Christophe Leroy Subject: [RFC PATCH v3 14/15] powerpc/syscall: Avoid stack frame in likely part of syscall_call_exception() To: Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , npiggin@gmail.com, msuchanek@suse.de Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org Date: Mon, 6 Apr 2020 18:16:50 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When r3 is not modified, reload it from regs->orig_r3 to free volatile registers. This avoids a stack frame for the likely part of syscall_call_exception() Before : 353 cycles on null_syscall After : 347 cycles on null_syscall Before the patch: c000b4d4 : c000b4d4: 7c 08 02 a6 mflr r0 c000b4d8: 94 21 ff e0 stwu r1,-32(r1) c000b4dc: 93 e1 00 1c stw r31,28(r1) c000b4e0: 90 01 00 24 stw r0,36(r1) c000b4e4: 90 6a 00 88 stw r3,136(r10) c000b4e8: 81 6a 00 84 lwz r11,132(r10) c000b4ec: 69 6b 00 02 xori r11,r11,2 c000b4f0: 55 6b ff fe rlwinm r11,r11,31,31,31 c000b4f4: 0f 0b 00 00 twnei r11,0 c000b4f8: 81 6a 00 a0 lwz r11,160(r10) c000b4fc: 55 6b 07 fe clrlwi r11,r11,31 c000b500: 0f 0b 00 00 twnei r11,0 c000b504: 7c 0c 42 e6 mftb r0 c000b508: 83 e2 00 08 lwz r31,8(r2) c000b50c: 81 82 00 28 lwz r12,40(r2) c000b510: 90 02 00 24 stw r0,36(r2) c000b514: 7d 8c f8 50 subf r12,r12,r31 c000b518: 7c 0c 02 14 add r0,r12,r0 c000b51c: 90 02 00 08 stw r0,8(r2) c000b520: 7c 10 13 a6 mtspr 80,r0 c000b524: 81 62 00 70 lwz r11,112(r2) c000b528: 71 60 86 91 andi. r0,r11,34449 c000b52c: 40 82 00 34 bne c000b560 c000b530: 2b 89 01 b6 cmplwi cr7,r9,438 c000b534: 41 9d 00 64 bgt cr7,c000b598 c000b538: 3d 40 c0 5c lis r10,-16292 c000b53c: 55 29 10 3a rlwinm r9,r9,2,0,29 c000b540: 39 4a 41 e8 addi r10,r10,16872 c000b544: 80 01 00 24 lwz r0,36(r1) c000b548: 7d 2a 48 2e lwzx r9,r10,r9 c000b54c: 7c 08 03 a6 mtlr r0 c000b550: 7d 29 03 a6 mtctr r9 c000b554: 83 e1 00 1c lwz r31,28(r1) c000b558: 38 21 00 20 addi r1,r1,32 c000b55c: 4e 80 04 20 bctr After the patch: c000b4d4 : c000b4d4: 81 6a 00 84 lwz r11,132(r10) c000b4d8: 90 6a 00 88 stw r3,136(r10) c000b4dc: 69 6b 00 02 xori r11,r11,2 c000b4e0: 55 6b ff fe rlwinm r11,r11,31,31,31 c000b4e4: 0f 0b 00 00 twnei r11,0 c000b4e8: 80 6a 00 a0 lwz r3,160(r10) c000b4ec: 54 63 07 fe clrlwi r3,r3,31 c000b4f0: 0f 03 00 00 twnei r3,0 c000b4f4: 7d 6c 42 e6 mftb r11 c000b4f8: 81 82 00 08 lwz r12,8(r2) c000b4fc: 80 02 00 28 lwz r0,40(r2) c000b500: 91 62 00 24 stw r11,36(r2) c000b504: 7c 00 60 50 subf r0,r0,r12 c000b508: 7d 60 5a 14 add r11,r0,r11 c000b50c: 91 62 00 08 stw r11,8(r2) c000b510: 7c 10 13 a6 mtspr 80,r0 c000b514: 80 62 00 70 lwz r3,112(r2) c000b518: 70 6b 86 91 andi. r11,r3,34449 c000b51c: 40 82 00 28 bne c000b544 c000b520: 2b 89 01 b6 cmplwi cr7,r9,438 c000b524: 41 9d 00 84 bgt cr7,c000b5a8 c000b528: 80 6a 00 88 lwz r3,136(r10) c000b52c: 3d 40 c0 5c lis r10,-16292 c000b530: 55 29 10 3a rlwinm r9,r9,2,0,29 c000b534: 39 4a 41 e4 addi r10,r10,16868 c000b538: 7d 2a 48 2e lwzx r9,r10,r9 c000b53c: 7d 29 03 a6 mtctr r9 c000b540: 4e 80 04 20 bctr Signed-off-by: Christophe Leroy --- arch/powerpc/kernel/syscall.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/arch/powerpc/kernel/syscall.c b/arch/powerpc/kernel/syscall.c index f9fca9985b0f..af449a4a8e8f 100644 --- a/arch/powerpc/kernel/syscall.c +++ b/arch/powerpc/kernel/syscall.c @@ -85,6 +85,9 @@ notrace long system_call_exception(long r3, long r4, long r5, } else if (unlikely(r0 >= NR_syscalls)) { return -ENOSYS; + } else { + /* Restore r3 from orig_gpr3 to free up a volatile reg */ + r3 = regs->orig_gpr3; } /* May be faster to do array_index_nospec? */ -- 2.25.0