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=-10.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_2 autolearn=unavailable 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 00773C433E0 for ; Thu, 14 Jan 2021 18:33:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B91A523B28 for ; Thu, 14 Jan 2021 18:33:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726310AbhANSdl (ORCPT ); Thu, 14 Jan 2021 13:33:41 -0500 Received: from frasgout.his.huawei.com ([185.176.79.56]:2352 "EHLO frasgout.his.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726035AbhANSdl (ORCPT ); Thu, 14 Jan 2021 13:33:41 -0500 Received: from fraeml705-chm.china.huawei.com (unknown [172.18.147.200]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4DGtB600Ldz67bhq; Fri, 15 Jan 2021 02:29:01 +0800 (CST) Received: from lhreml710-chm.china.huawei.com (10.201.108.61) by fraeml705-chm.china.huawei.com (10.206.15.54) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2106.2; Thu, 14 Jan 2021 19:32:57 +0100 Received: from localhost (10.47.30.252) by lhreml710-chm.china.huawei.com (10.201.108.61) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256) id 15.1.2106.2; Thu, 14 Jan 2021 18:32:57 +0000 Date: Thu, 14 Jan 2021 18:32:17 +0000 From: Jonathan Cameron To: Ben Widawsky CC: , , , , Ira Weiny , Dan Williams , "Vishal Verma" , "Kelley, Sean V" , Rafael Wysocki , "Bjorn Helgaas" , Jon Masters , Chris Browy , Randy Dunlap , "Christoph Hellwig" , Subject: Re: [RFC PATCH v3 14/16] cxl/mem: Use CEL for enabling commands Message-ID: <20210114183217.0000154c@Huawei.com> In-Reply-To: <20210114181340.fgybdchzfxiiqwhr@intel.com> References: <20210111225121.820014-1-ben.widawsky@intel.com> <20210111225121.820014-16-ben.widawsky@intel.com> <20210114180211.00007852@Huawei.com> <20210114181340.fgybdchzfxiiqwhr@intel.com> Organization: Huawei Technologies Research and Development (UK) Ltd. X-Mailer: Claws Mail 3.17.4 (GTK+ 2.24.32; i686-w64-mingw32) MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.47.30.252] X-ClientProxiedBy: lhreml709-chm.china.huawei.com (10.201.108.58) To lhreml710-chm.china.huawei.com (10.201.108.61) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org On Thu, 14 Jan 2021 10:13:40 -0800 Ben Widawsky wrote: > On 21-01-14 18:02:11, Jonathan Cameron wrote: > > On Mon, 11 Jan 2021 14:51:19 -0800 > > Ben Widawsky wrote: > > > > > The Command Effects Log (CEL) is specified in the CXL 2.0 specification. > > > The CEL is one of two types of logs, the other being vendor specific. > > > They are distinguished in hardware/spec via UUID. The CEL is immediately > > > useful for 2 things: > > > 1. Determine which optional commands are supported by the CXL device. > > > 2. Enumerate any vendor specific commands > > > > > > The CEL can be used by the driver to determine which commands are > > > available in the hardware (though it isn't, yet). That set of commands > > > might itself be a subset of commands which are available to be used via > > > CXL_MEM_SEND_COMMAND IOCTL. > > > > > > Prior to this, all commands that the driver exposed were explicitly > > > enabled. After this, only those commands that are found in the CEL are > > > enabled. > > > > > > Signed-off-by: Ben Widawsky > > > > This patch made me wonder if the model for the command in quite right. > > I think it would end up simpler with a pair of payload pointers for send > > and receive (that can be equal when it makes sense). > > > > A few other things inline. > > > > Jonathan > > I'll address the others separately, but could you elaborate on this? I'm not > sure I follow your meaning. Further down in the review.. " The fact that you end up bypassing the payload transfer stuff in mbox_cmd rather suggests it's not a particularly good model. + it keeps confusing me. While the hardware uses a single region for the payload, there is nothing saying the code has to work that way. Why not have separate payload_in and payload_out pointers? Occasionally you might set them to the same buffer, but elsewhere you could avoid the direct memcpy()s you are doing around the send_cmd(). " Jonathan > > [snip] > >