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=-9.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, UNPARSEABLE_RELAY,USER_AGENT_GIT 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 47F33C2D0DB for ; Thu, 30 Jan 2020 13:09:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1FCCB2082E for ; Thu, 30 Jan 2020 13:09:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727321AbgA3NJJ (ORCPT ); Thu, 30 Jan 2020 08:09:09 -0500 Received: from out30-132.freemail.mail.aliyun.com ([115.124.30.132]:51125 "EHLO out30-132.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726980AbgA3NJI (ORCPT ); Thu, 30 Jan 2020 08:09:08 -0500 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R101e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e07484;MF=wenyang@linux.alibaba.com;NM=1;PH=DS;RN=7;SR=0;TI=SMTPD_---0TomDHZ2_1580389719; Received: from localhost(mailfrom:wenyang@linux.alibaba.com fp:SMTPD_---0TomDHZ2_1580389719) by smtp.aliyun-inc.com(127.0.0.1); Thu, 30 Jan 2020 21:08:46 +0800 From: Wen Yang To: Thomas Gleixner , Borislav Petkov , hpa@zytor.com, Ingo Molnar Cc: Wen Yang , x86@kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] x86/tsc: improve arithmetic division Date: Thu, 30 Jan 2020 21:08:38 +0800 Message-Id: <20200130130838.29157-1-wenyang@linux.alibaba.com> X-Mailer: git-send-email 2.23.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org do_div() does a 64-by-32 division. Use div64_ul64() or div64_ul() instead of it if the divisor is 'ul64' or 'unsigned long', to avoid truncation to lower 32-bit. And as a nice side effect also cleans up the function a bit. Signed-off-by: Wen Yang Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Borislav Petkov Cc: "H. Peter Anvin" Cc: x86@kernel.org Cc: linux-kernel@vger.kernel.org --- arch/x86/kernel/tsc.c | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-) diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c index 7e322e2daaf5..4c0320e68699 100644 --- a/arch/x86/kernel/tsc.c +++ b/arch/x86/kernel/tsc.c @@ -357,9 +357,7 @@ static unsigned long calc_pmtimer_ref(u64 deltatsc, u64 pm1, u64 pm2) pm2 -= pm1; tmp = pm2 * 1000000000LL; do_div(tmp, PMTMR_TICKS_PER_SEC); - do_div(deltatsc, tmp); - - return (unsigned long) deltatsc; + return (unsigned long) div64_u64(deltatsc, tmp); } #define CAL_MS 10 @@ -778,8 +776,7 @@ static unsigned long pit_hpet_ptimer_calibrate_cpu(void) tsc_ref_min = min(tsc_ref_min, (unsigned long) tsc2); /* Check the reference deviation */ - delta = ((u64) tsc_pit_min) * 100; - do_div(delta, tsc_ref_min); + delta = div64_ul(((u64) tsc_pit_min) * 100, tsc_ref_min); /* * If both calibration results are inside a 10% window -- 2.23.0