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 1A99CC47257 for ; Sun, 3 May 2020 20:20:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F1153206F1 for ; Sun, 3 May 2020 20:20:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729140AbgECUUY convert rfc822-to-8bit (ORCPT ); Sun, 3 May 2020 16:20:24 -0400 Received: from mail.fireflyinternet.com ([109.228.58.192]:52747 "EHLO fireflyinternet.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1729080AbgECUUX (ORCPT ); Sun, 3 May 2020 16:20:23 -0400 X-Default-Received-SPF: pass (skip=forwardok (res=PASS)) x-ip-name=78.156.65.138; Received: from localhost (unverified [78.156.65.138]) by fireflyinternet.com (Firefly Internet (M1)) with ESMTP (TLS) id 21101043-1500050 for multiple; Sun, 03 May 2020 21:20:21 +0100 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8BIT In-Reply-To: <20200501180731.GA2485@infradead.org> References: <20200430221016.3866-1-Jason@zx2c4.com> <20200501180731.GA2485@infradead.org> To: "Jason A. Donenfeld" , Christoph Hellwig Subject: Re: [PATCH] drm/i915: check to see if SIMD registers are available before using SIMD Cc: linux-kernel@vger.kernel.org, intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, bigeasy@linutronix.de, tglx@linutronix.de, stable@vger.kernel.org From: Chris Wilson Message-ID: <158853721918.8377.18286963845226122104@build.alporthouse.com> User-Agent: alot/0.8.1 Date: Sun, 03 May 2020 21:20:19 +0100 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Quoting Christoph Hellwig (2020-05-01 19:07:31) > On Thu, Apr 30, 2020 at 04:10:16PM -0600, Jason A. Donenfeld wrote: > > Sometimes it's not okay to use SIMD registers, the conditions for which > > have changed subtly from kernel release to kernel release. Usually the > > pattern is to check for may_use_simd() and then fallback to using > > something slower in the unlikely case SIMD registers aren't available. > > So, this patch fixes up i915's accelerated memcpy routines to fallback > > to boring memcpy if may_use_simd() is false. > > Err, why does i915 implements its own uncached memcpy instead of relying > on core functionality to start with? What is this core functionality that provides movntqda? -Chris