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=-2.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 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 C118EC43603 for ; Fri, 20 Dec 2019 18:24:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 98E6F206EF for ; Fri, 20 Dec 2019 18:24:26 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=c-s.fr header.i=@c-s.fr header.b="UQSAR4p4" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727467AbfLTSYZ (ORCPT ); Fri, 20 Dec 2019 13:24:25 -0500 Received: from pegase1.c-s.fr ([93.17.236.30]:22095 "EHLO pegase1.c-s.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727390AbfLTSYZ (ORCPT ); Fri, 20 Dec 2019 13:24:25 -0500 Received: from localhost (mailhub1-ext [192.168.12.233]) by localhost (Postfix) with ESMTP id 47fcb93TxXz9vBmy; Fri, 20 Dec 2019 19:24:21 +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=UQSAR4p4; 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 G_xgQVgyxqbB; Fri, 20 Dec 2019 19:24:21 +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 47fcb929LGz9vBmw; Fri, 20 Dec 2019 19:24:21 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=c-s.fr; s=mail; t=1576866261; bh=Su70azpqiUzym4+ORB2ehXEC+XGge58TLbE3wNLj9xE=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=UQSAR4p4lj9J1aElN4XaeC8Kx1TiV3+fqtZN9BKoJ2Yy5ch6j7vTrDbySzVT8JBAI /Z5ayLabksz0vi+B534APGY/Ks6HTT+CyIjuGmTRBnLXjGstp2lQilEGIuQpRDqMbz fCAyiU3rdzQw5Q6q+E1FxMWa1j07voEda/3v0SIo= Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 0B49F8B86D; Fri, 20 Dec 2019 19:24:23 +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 Txi8Jrl5ZLDO; Fri, 20 Dec 2019 19:24:22 +0100 (CET) Received: from [192.168.4.90] (unknown [192.168.4.90]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 633C38B867; Fri, 20 Dec 2019 19:24:22 +0100 (CET) Subject: Re: [RFC PATCH] powerpc/32: Switch VDSO to C implementation. To: Thomas Gleixner Cc: Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , vincenzo.frascino@arm.com, luto@kernel.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org References: <8ce3582f7f7da9ff0286ced857e5aa2e5ae6746e.1571662378.git.christophe.leroy@c-s.fr> <95bd2367-8edc-29db-faa3-7729661e05f2@c-s.fr> <439bce37-9c2c-2afe-9c9e-2f500472f9f8@c-s.fr> From: Christophe Leroy Message-ID: <207cef10-3da8-6a52-139c-0620b21b64af@c-s.fr> Date: Fri, 20 Dec 2019 19:24:22 +0100 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.9.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: fr Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Thomas, In do_hres(), I see: cycles = __arch_get_hw_counter(vd->clock_mode); ns = vdso_ts->nsec; last = vd->cycle_last; if (unlikely((s64)cycles < 0)) return -1; __arch_get_hw_counter() returns a u64 values. On the PPC, this is read from the timebase which is a 64 bits counter. Why returning -1 if (s64)cycles < 0 ? Does it means we have to mask out the most significant bit when reading the HW counter ? Christophe 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=-2.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 A5BDDC43603 for ; Fri, 20 Dec 2019 18:26:37 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 23CD621655 for ; Fri, 20 Dec 2019 18:26:36 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=c-s.fr header.i=@c-s.fr header.b="UQSAR4p4" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 23CD621655 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=c-s.fr Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 47fcdk6chbzDqt3 for ; Sat, 21 Dec 2019 05:26:34 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=c-s.fr (client-ip=93.17.236.30; helo=pegase1.c-s.fr; envelope-from=christophe.leroy@c-s.fr; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=c-s.fr Authentication-Results: lists.ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=c-s.fr header.i=@c-s.fr header.b="UQSAR4p4"; dkim-atps=neutral Received: from pegase1.c-s.fr (pegase1.c-s.fr [93.17.236.30]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 47fcbL4PfFzDqs1 for ; Sat, 21 Dec 2019 05:24:28 +1100 (AEDT) Received: from localhost (mailhub1-ext [192.168.12.233]) by localhost (Postfix) with ESMTP id 47fcb93TxXz9vBmy; Fri, 20 Dec 2019 19:24:21 +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=UQSAR4p4; 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 G_xgQVgyxqbB; Fri, 20 Dec 2019 19:24:21 +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 47fcb929LGz9vBmw; Fri, 20 Dec 2019 19:24:21 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=c-s.fr; s=mail; t=1576866261; bh=Su70azpqiUzym4+ORB2ehXEC+XGge58TLbE3wNLj9xE=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=UQSAR4p4lj9J1aElN4XaeC8Kx1TiV3+fqtZN9BKoJ2Yy5ch6j7vTrDbySzVT8JBAI /Z5ayLabksz0vi+B534APGY/Ks6HTT+CyIjuGmTRBnLXjGstp2lQilEGIuQpRDqMbz fCAyiU3rdzQw5Q6q+E1FxMWa1j07voEda/3v0SIo= Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 0B49F8B86D; Fri, 20 Dec 2019 19:24:23 +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 Txi8Jrl5ZLDO; Fri, 20 Dec 2019 19:24:22 +0100 (CET) Received: from [192.168.4.90] (unknown [192.168.4.90]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 633C38B867; Fri, 20 Dec 2019 19:24:22 +0100 (CET) Subject: Re: [RFC PATCH] powerpc/32: Switch VDSO to C implementation. To: Thomas Gleixner References: <8ce3582f7f7da9ff0286ced857e5aa2e5ae6746e.1571662378.git.christophe.leroy@c-s.fr> <95bd2367-8edc-29db-faa3-7729661e05f2@c-s.fr> <439bce37-9c2c-2afe-9c9e-2f500472f9f8@c-s.fr> From: Christophe Leroy Message-ID: <207cef10-3da8-6a52-139c-0620b21b64af@c-s.fr> Date: Fri, 20 Dec 2019 19:24:22 +0100 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.9.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: fr Content-Transfer-Encoding: 7bit X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-kernel@vger.kernel.org, Paul Mackerras , luto@kernel.org, vincenzo.frascino@arm.com, linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Hi Thomas, In do_hres(), I see: cycles = __arch_get_hw_counter(vd->clock_mode); ns = vdso_ts->nsec; last = vd->cycle_last; if (unlikely((s64)cycles < 0)) return -1; __arch_get_hw_counter() returns a u64 values. On the PPC, this is read from the timebase which is a 64 bits counter. Why returning -1 if (s64)cycles < 0 ? Does it means we have to mask out the most significant bit when reading the HW counter ? Christophe