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 B31E2C433F5 for ; Sun, 26 Aug 2018 14:06:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5E9D9208B6 for ; Sun, 26 Aug 2018 14:06:51 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5E9D9208B6 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linutronix.de 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 S1727053AbeHZRt3 (ORCPT ); Sun, 26 Aug 2018 13:49:29 -0400 Received: from Galois.linutronix.de ([146.0.238.70]:41771 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726373AbeHZRt3 (ORCPT ); Sun, 26 Aug 2018 13:49:29 -0400 Received: from p4fea45ac.dip0.t-ipconnect.de ([79.234.69.172] helo=nanos.glx-home) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1ftvgh-0005hr-5t; Sun, 26 Aug 2018 16:06:43 +0200 Date: Sun, 26 Aug 2018 16:06:32 +0200 (CEST) From: Thomas Gleixner To: "Jason A. Donenfeld" cc: LKML , Netdev , David Miller , Andrew Lutomirski , Greg Kroah-Hartman , Samuel Neves , linux-arch@vger.kernel.org, Rik van Riel Subject: Re: [PATCH v2 01/17] asm: simd context helper API In-Reply-To: Message-ID: References: <20180824213849.23647-1-Jason@zx2c4.com> <20180824213849.23647-2-Jason@zx2c4.com> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Jason, On Sun, 26 Aug 2018, Jason A. Donenfeld wrote: > On Sun, Aug 26, 2018 at 6:10 AM Thomas Gleixner wrote: > > I'm not too fond of this simply because it requires that relax() step in > > all code pathes. I'd rather make that completely transparent by just > > marking the task as FPU using and let the context switch code deal with it > > in case that it gets preempted. I'll let one of my engineers look into > > that next week. > > Do you mean to say you intend to make kernel_fpu_end() and > kernel_neon_end() only actually do something upon context switch, but > not when it's actually called? So that multiple calls to > kernel_fpu_begin() and kernel_neon_begin() can be made without > penalty? On context switch and exit to user. That allows to keep those code pathes fully preemptible. Still twisting my brain around the details. > If so, that'd be great, and I'd certainly prefer this to the > simd_context_t passing. I consider the simd_get/put/relax API a > stopgap measure until something like that is implemented. I really want to avoid this stopgap^Wducttape thing. Thanks, tglx