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=-2.2 required=3.0 tests=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 D3EBDECE58E for ; Thu, 17 Oct 2019 09:46:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AC2B320650 for ; Thu, 17 Oct 2019 09:46:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404836AbfJQJqF (ORCPT ); Thu, 17 Oct 2019 05:46:05 -0400 Received: from [217.140.110.172] ([217.140.110.172]:37262 "EHLO foss.arm.com" rhost-flags-FAIL-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1727349AbfJQJqE (ORCPT ); Thu, 17 Oct 2019 05:46:04 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 539C519BF; Thu, 17 Oct 2019 02:45:48 -0700 (PDT) Received: from [192.168.1.103] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 271BD3F718; Thu, 17 Oct 2019 02:45:43 -0700 (PDT) Subject: Re: [PATCHv7 01/33] ns: Introduce Time Namespace To: Thomas Gleixner , Andrei Vagin Cc: Dmitry Safonov , linux-kernel@vger.kernel.org, Dmitry Safonov <0x7f454c46@gmail.com>, Andrei Vagin , Adrian Reber , Andy Lutomirski , Arnd Bergmann , Christian Brauner , Cyrill Gorcunov , "Eric W. Biederman" , "H. Peter Anvin" , Ingo Molnar , Jann Horn , Jeff Dike , Oleg Nesterov , Pavel Emelyanov , Shuah Khan , containers@lists.linux-foundation.org, criu@openvz.org, linux-api@vger.kernel.org, x86@kernel.org References: <20191011012341.846266-1-dima@arista.com> <20191011012341.846266-2-dima@arista.com> <80af93da-d497-81de-2a2a-179bb3bc852d@arm.com> <20191016233342.GA3075@gmail.com> From: Vincenzo Frascino Message-ID: <406b77c3-46c5-e0ff-c658-04cdb99200b4@arm.com> Date: Thu, 17 Oct 2019 10:47:36 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/17/19 10:20 AM, Thomas Gleixner wrote: [...] > The architectures which implement VDSO are: > > arm, arm64, mips, nds32, powerpc, riscv, s390, sparc, x86, um > > arm64, mips, x86 use the generic VDSO. Patches for arm are floating > around. UM is special as it just traps into the syscalls. No idea about the > rest. Vincenzo might know. > There a couple of cases: hexagon and csky that have vDSOs for signal trampolines if I recall correctly, but they do not fall into the category we are exploring at the moment. > The bad news is that we have no information (except on arm which has a > config switch for VDSO) whether an architecture provides VDSO support or > not. > > So unless you add something like > > config HAS_VDSO > bool > > which is selected by all architectures which provide VDSO support, the only > sane solution is to depend on GENERIC_VDSO_TIME_NS. > > TBH, I would not even bother. The architectures which matter and are going > to use time namespaces already support VDSO and they need to move to the > generic implementation anyway as we discussed and agreed on in Vancouver. > > Providing time name spaces for the non VDSO archs is a purely academic > exercise. I totally agree with this. -- Regards, Vincenzo