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=-3.8 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no 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 DBE6DC433E2 for ; Wed, 15 Jul 2020 08:38:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A395D2065D for ; Wed, 15 Jul 2020 08:38:20 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="tpJhfIRz" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730283AbgGOIiT (ORCPT ); Wed, 15 Jul 2020 04:38:19 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53668 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729066AbgGOIiS (ORCPT ); Wed, 15 Jul 2020 04:38:18 -0400 Received: from merlin.infradead.org (merlin.infradead.org [IPv6:2001:8b0:10b:1231::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3DA65C061755 for ; Wed, 15 Jul 2020 01:38:18 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=0kjsVOfV30caO/5Zchs4MAMTJc5SZZBY2bLlqPn+b6U=; b=tpJhfIRz2E8zQ08WOsHHmIFe5n n9VDMj5cagstx5VgIfC8HrUizrdH2KsxuEcSQ3kqH1OGGV4BmDaQo1O6T7I1bvC989Ir6Jp7Gzubw 0psAguRiKJMhYikHNoyv5ZHNTXFbaBbj1etTPSQjmrV74UUNsc3zRD6pX7pSjPhWOzuE5F5BPVf9W y5rD+K6aWXI7tPr4Ak21vZ8NZHN+X84PkS/C/ZUgWd2nlfM/w3hxxRWBZhKZETjUJod2xVJQq0yTW uSMvVysCOzvfoN+FaQKelHCUlAOedsCbHLsgL3WbnzgfKYhkquEqPJjEfhp9VOsuEMy7Kulb/aEJj eC6sUKAQ==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jvcvV-0000Bo-Oa; Wed, 15 Jul 2020 08:38:05 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id F2B1A300446; Wed, 15 Jul 2020 10:38:00 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id B270023648708; Wed, 15 Jul 2020 10:38:00 +0200 (CEST) Date: Wed, 15 Jul 2020 10:38:00 +0200 From: Peter Zijlstra To: Leo Yan Cc: Will Deacon , Mark Rutland , Ingo Molnar , Arnaldo Carvalho de Melo , Alexander Shishkin , Jiri Olsa , Namhyung Kim , Catalin Marinas , Thomas Gleixner , Paul Cercueil , "Ben Dooks (Codethink)" , "Ahmed S. Darwish" , Adrian Hunter , Kan Liang , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 2/6] arm64: perf: Implement correct cap_user_time Message-ID: <20200715083800.GC10769@hirez.programming.kicks-ass.net> References: <20200715020512.20991-1-leo.yan@linaro.org> <20200715020512.20991-3-leo.yan@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200715020512.20991-3-leo.yan@linaro.org> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 15, 2020 at 10:05:08AM +0800, Leo Yan wrote: > [leoyan: Use quot/rem to convert cyc to ns to avoid overflow] > + quot = rd->epoch_cyc >> rd->shift; > + rem = rd->epoch_cyc & (((u64)1 << rd->shift) - 1); > + ns = quot * rd->mult + ((rem * rd->mult) >> rd->shift); > + userpg->time_zero -= ns; I think we have mul_u64_u32_shr() for that.