From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from dispatch1-us1.ppe-hosted.com (dispatch1-us1.ppe-hosted.com [67.231.154.164]) by dpdk.org (Postfix) with ESMTP id B368A1B01E for ; Fri, 19 Jan 2018 08:16:31 +0100 (CET) X-Virus-Scanned: Proofpoint Essentials engine Received: from webmail.solarflare.com (uk.solarflare.com [193.34.186.16]) (using TLSv1 with cipher ECDHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1-us3.ppe-hosted.com (Proofpoint Essentials ESMTP Server) with ESMTPS id 85BEA6C0062; Fri, 19 Jan 2018 07:16:30 +0000 (UTC) Received: from [192.168.38.17] (84.52.114.114) by ukex01.SolarFlarecom.com (10.17.10.4) with Microsoft SMTP Server (TLS) id 15.0.1044.25; Fri, 19 Jan 2018 07:16:22 +0000 To: Yongseok Koh , , , , , , , CC: References: <20180116011050.18866-1-yskoh@mellanox.com> <20180119004430.15305-1-yskoh@mellanox.com> <20180119004430.15305-2-yskoh@mellanox.com> From: Andrew Rybchenko Message-ID: <805e1578-6e4d-6a1b-00ce-13e3b1c16be8@solarflare.com> Date: Fri, 19 Jan 2018 10:16:17 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.5.2 MIME-Version: 1.0 In-Reply-To: <20180119004430.15305-2-yskoh@mellanox.com> Content-Language: en-GB X-Originating-IP: [84.52.114.114] X-ClientProxiedBy: ocex03.SolarFlarecom.com (10.20.40.36) To ukex01.SolarFlarecom.com (10.17.10.4) X-TM-AS-Product-Ver: SMEX-11.0.0.1191-8.100.1062-23606.003 X-TM-AS-Result: No--9.823100-0.000000-31 X-TM-AS-User-Approved-Sender: Yes X-TM-AS-User-Blocked-Sender: No X-MDID: 1516346191-uN8ZbPHblkjL Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 8bit X-Content-Filtered-By: Mailman/MimeDel 2.1.15 Subject: Re: [dpdk-dev] [PATCH v3 1/8] eal: introduce DMA memory barriers X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 19 Jan 2018 07:16:31 -0000 On 01/19/2018 03:44 AM, Yongseok Koh wrote: > This commit introduces rte_dma_wmb() and rte_dma_rmb(), in order to > guarantee the ordering of coherent shared memory between the CPU and a DMA > capable device. > > Signed-off-by: Yongseok Koh Acked-by: Andrew Rybchenko It is already really good. Many thanks. Maybe it would be useful to:  - avoid duplication of so long explanations (put in in one place and add reference?)  - explain why it is bound to DMA or call it in a different way, since right now it is bound    to coherent-mapped IO (rte_cio_rmb() ?). Yes, I see benefits to follow Linux    terminology, but may be DPDK can do better :) I just add my concerns, but let    EAL code maintainers to decide  - as I understand right now there is no control over DMA mapping since    mapping is done by UIO/VFIO drivers. Should documentation be updated that    DMA mapping is assumed to be coherent?  - when it is applied, may be it makes sense to send HEADS UP to dev@,    it definitely deserves to be mentioned in the release notes <...>