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,URIBL_BLOCKED,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 C18E6C432C0 for ; Thu, 21 Nov 2019 00:53:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 88B9D20730 for ; Thu, 21 Nov 2019 00:53:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726333AbfKUAxP (ORCPT ); Wed, 20 Nov 2019 19:53:15 -0500 Received: from Galois.linutronix.de ([193.142.43.55]:59348 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726202AbfKUAxP (ORCPT ); Wed, 20 Nov 2019 19:53:15 -0500 Received: from p5b06da22.dip0.t-ipconnect.de ([91.6.218.34] helo=nanos) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1iXaie-0001UQ-Ct; Thu, 21 Nov 2019 01:53:12 +0100 Date: Thu, 21 Nov 2019 01:53:11 +0100 (CET) From: Thomas Gleixner To: Dan Williams cc: Borislav Petkov , "Luck, Tony" , Dave Jiang , dmaengine@vger.kernel.org, Linux Kernel Mailing List , Vinod Koul , Jing Lin , "Raj, Ashok" , "Kumar, Sanjay K" , "Dey, Megha" , "Pan, Jacob jun" , "Liu, Yi L" , Jens Axboe , Andrew Morton , Ingo Molnar , Fenghua Yu , "H. Peter Anvin" Subject: Re: [PATCH RFC 01/14] x86/asm: add iosubmit_cmds512() based on movdir64b CPU instruction In-Reply-To: Message-ID: References: <157428480574.36836.14057238306923901253.stgit@djiang5-desk3.ch.intel.com> <157428502934.36836.8119026517510193201.stgit@djiang5-desk3.ch.intel.com> <20191120215338.GN2634@zn.tnic> <20191120231923.GA32680@agluck-desk2.amr.corp.intel.com> <20191120232645.GO2634@zn.tnic> 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: dmaengine-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: dmaengine@vger.kernel.org On Wed, 20 Nov 2019, Dan Williams wrote: > On Wed, Nov 20, 2019 at 3:27 PM Borislav Petkov wrote: > > > > On Wed, Nov 20, 2019 at 03:19:23PM -0800, Luck, Tony wrote: > > > That's the underlying functionality of the MOVDIR64B instruction. A > > > posted write so no way to know if it succeeded. > > > > So how do you know whether any of the writes went through? > > It's identical to the writel() mmio-write to start a SATA command > transfer. The higher level device driver protocol validates that the > command went through, ultimately with a timeout. There's no return > value for iosubmit_cmds512() for the same reason there's no return > value for the other iowrite primitives. With the difference that other iowrite primitive have no dependencies on cpu feature bits and cannot fail on the software level. Thanks, tglx