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_PASS 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 B9E5CECDFD0 for ; Fri, 14 Sep 2018 13:06:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7D8A821476 for ; Fri, 14 Sep 2018 13:06:53 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7D8A821476 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728188AbeINSVP (ORCPT ); Fri, 14 Sep 2018 14:21:15 -0400 Received: from mx1.redhat.com ([209.132.183.28]:38302 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727013AbeINSVP (ORCPT ); Fri, 14 Sep 2018 14:21:15 -0400 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 22B8730832F2; Fri, 14 Sep 2018 13:06:51 +0000 (UTC) Received: from oldenburg.str.redhat.com (ovpn-116-110.ams2.redhat.com [10.36.116.110]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 4602427C3E; Fri, 14 Sep 2018 13:06:48 +0000 (UTC) Subject: Re: [patch 00/11] x86/vdso: Cleanups, simmplifications and CLOCK_TAI support To: Thomas Gleixner Cc: LKML , Andy Lutomirski , x86@kernel.org, Peter Zijlstra , Matt Rickard , Stephen Boyd , John Stultz , "K. Y. Srinivasan" , Vitaly Kuznetsov , devel@linuxdriverproject.org, virtualization@lists.linux-foundation.org, Paolo Bonzini , Arnd Bergmann , Juergen Gross References: <20180914125006.349747096@linutronix.de> <2f723b28-8f81-4b02-861c-42f756a8825a@redhat.com> From: Florian Weimer Message-ID: <63a0f67d-fdb1-e2fc-5d4d-4f3cfbf86fd1@redhat.com> Date: Fri, 14 Sep 2018 15:06:46 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.44]); Fri, 14 Sep 2018 13:06:51 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/14/2018 03:05 PM, Thomas Gleixner wrote: > On Fri, 14 Sep 2018, Florian Weimer wrote: > >> On 09/14/2018 02:50 PM, Thomas Gleixner wrote: >>> Matt attempted to add CLOCK_TAI support to the VDSO clock_gettime() >>> implementation, which extended the clockid switch case and added yet >>> another slightly different copy of the same code. >>> >>> Especially the extended switch case is problematic as the compiler tends to >>> generate a jump table which then requires to use retpolines. >> >> Does vDSO code really have to use retpolines? It's in userspace, after all. > > Unless you have IBRS/STIPB enabled, you need user space ratpoutine as well. I don't think this is a consensus position, and it obviously depends on the (sub)architecture. Thanks, Florian