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=-0.8 required=3.0 tests=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 0F308C33CB3 for ; Thu, 16 Jan 2020 10:35:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D96922072B for ; Thu, 16 Jan 2020 10:35:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726410AbgAPKfg convert rfc822-to-8bit (ORCPT ); Thu, 16 Jan 2020 05:35:36 -0500 Received: from Galois.linutronix.de ([193.142.43.55]:51161 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725800AbgAPKff (ORCPT ); Thu, 16 Jan 2020 05:35:35 -0500 Received: from [5.158.153.52] (helo=nanos.tec.linutronix.de) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1is2Uf-00048X-Ra; Thu, 16 Jan 2020 11:35:17 +0100 Received: by nanos.tec.linutronix.de (Postfix, from userid 1000) id 7755E101B66; Thu, 16 Jan 2020 11:35:17 +0100 (CET) From: Thomas Gleixner To: Christophe Leroy , luto@kernel.org Cc: Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , arnd@arndb.de, vincenzo.frascino@arm.com, x86@kernel.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mips@vger.kernel.org Subject: Re: [RFC PATCH v3 08/12] lib: vdso: allow arches to provide vdso data pointer In-Reply-To: References: <381e547dbb3c48fd39d6cf208033bba38ad048fb.1578934751.git.christophe.leroy@c-s.fr> <87ftghbpuu.fsf@nanos.tec.linutronix.de> Date: Thu, 16 Jan 2020 11:35:17 +0100 Message-ID: <87k15rwuxm.fsf@nanos.tec.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Christophe Leroy writes: > Le 15/01/2020 à 07:15, Christophe Leroy a écrit : > From your point of view, what should I do: > A/ __arch_get_vdso_data() handled entirely at arch level and arches > handing over the vdso data pointer to generic C VDSO functions all the > time (as in my v2 series) ? No. That's again moving the same code to all architectures. > B/ Data pointer being handed over all the way up for arches wanting to > do so, no changes at all for others (as in my v3 series) ? Too much ifdeffery > C/ __arch_get_vdso_data() being called at the outermost generic level > for arches not interested in handling data pointer from the caller (as > suggested by Thomas) ? > > Andy, with A/ you were concerned about arches being able to do PC > related accesses. Would it be an issue for C/ as well ? If not, I guess > C/ would be cleaner than B/ allthought not as clean as A which doesn't > add any #ifdefery at all. You can avoid ifdeffery with C if you do: static __maybe_unused int __cvdso_data_clock_gettime(clockid_t clock, struct __kernel_timespec *ts, const struct vdso_data *vd) { ..... } static __maybe_unused int __cvdso_clock_gettime(clockid_t clock, struct __kernel_timespec *ts) { const struct vdso_data *vd = __arch_get_vdso_data(); return __cvdso_data_clock_gettime(clock, ts, vd); } and then use __cvdso_data_clock_gettime on PPC and let the other archs unmodified. Thanks, tglx