Received: by 2002:a25:8b91:0:0:0:0:0 with SMTP id j17csp7671732ybl; Tue, 24 Dec 2019 06:47:59 -0800 (PST) X-Google-Smtp-Source: APXvYqwNzKwxLD/vwnk1WAYZ2LsDFMHjf/92tsI/OHvYIeUb32LLxPgQCphJBEX0PMIORDBd2On+ X-Received: by 2002:a05:6830:1bf2:: with SMTP id k18mr37896535otb.36.1577198879063; Tue, 24 Dec 2019 06:47:59 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1577198879; cv=none; d=google.com; s=arc-20160816; b=mR7bQBLSmaqe3NecH7KbvRebumm/KKW93hvQQLX8ioR2r8YFLbCVVANfXKNnAg6nti 15TtoPg7F1qxZzXRnCfl1yZw+YXVaZlJnvuXxgQn0qYN9aO679f88Cv+ci3/Daw1uUYd BoRPd4udSMPW0ycWV6yI+SxOWBcPXnJeq+PTiV5iEt2bjR585Q6n7MoKGe6vv0R9+c/c OvlHOgKy9fxw2z3lBSt/QUpGOOIib8UFMXu/vl83TrQdq1yj5OWqcMIw+8QRL8jKCrI+ pW33ebVDrIkFv9luShluzttXNpTDJWal2x/0el/LMPk2KUQWIhBsZXUfM9Y+ACvX+ZPc wxlA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:sender:user-agent:in-reply-to :content-transfer-encoding:content-disposition:mime-version :references:message-id:subject:cc:to:from:date; bh=FiDAuWvA07aGal85vOdIm7BDCJvUNNNY7/0mdu0zp30=; b=kJhZ7y9ZVF08QllQx5biW9lPU5HEdAp+CJtxbOgUerVDoDuVYcJdRljnjWIDHuW1fq C0VQNlHr6KyMDiDzalVkceDunSaW2ZGva/c1p9H0oKTMFY1Staxjjz8opy/nKgu54VMP wBFIxs/ypqHWKyI9jiV8X5hxdy9xzk4o/VqCvNYfHGvy6B0E2NjToHtNkPiLW7YxxH/A o+gvNMLnu1CWx+rhouEzEr/QslDwyGqMPYmSsueiX53C9xLTw67CLSuPtH/GRMd3A7+2 /RAbMdt2a76ZMdGmdZtgCttBNP+q1A+0+TRW/y2XChfie3v2YSVoTQhi26tUXZ6+H7A7 iqKw== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Return-Path: Received: from vger.kernel.org (vger.kernel.org. [209.132.180.67]) by mx.google.com with ESMTP id z4si10206314oix.48.2019.12.24.06.47.46; Tue, 24 Dec 2019 06:47:59 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726213AbfLXOrH (ORCPT + 99 others); Tue, 24 Dec 2019 09:47:07 -0500 Received: from gate.crashing.org ([63.228.1.57]:48282 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726128AbfLXOrH (ORCPT ); Tue, 24 Dec 2019 09:47:07 -0500 Received: from gate.crashing.org (localhost.localdomain [127.0.0.1]) by gate.crashing.org (8.14.1/8.14.1) with ESMTP id xBOEkNuV031561; Tue, 24 Dec 2019 08:46:23 -0600 Received: (from segher@localhost) by gate.crashing.org (8.14.1/8.14.1/Submit) id xBOEkMoQ031560; Tue, 24 Dec 2019 08:46:22 -0600 X-Authentication-Warning: gate.crashing.org: segher set sender to segher@kernel.crashing.org using -f Date: Tue, 24 Dec 2019 08:46:21 -0600 From: Segher Boessenkool To: Andy Lutomirski Cc: christophe leroy , Arnd Bergmann , X86 ML , LKML , "open list:MIPS" , Paul Mackerras , Andy Lutomirski , Thomas Gleixner , Vincenzo Frascino , linuxppc-dev , linux-arm-kernel Subject: Re: [RFC PATCH v2 04/10] lib: vdso: get pointer to vdso data from the arch Message-ID: <20191224144621.GG4505@gate.crashing.org> References: Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.4.2.3i Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Dec 24, 2019 at 08:15:11PM +0800, Andy Lutomirski wrote: > Does power have PC-relative data access? If so, I wonder if the code can be arranged so that even the array accesses don’t require computing an absolute address at any point. Not before ISA 3.0 (that is Power9). The bcl/mflr dance isn't *that* expensive, if you use it sparingly. Segher