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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,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 5A33CC433E1 for ; Thu, 25 Jun 2020 00:42:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 338E520849 for ; Thu, 25 Jun 2020 00:42:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388942AbgFYAma (ORCPT ); Wed, 24 Jun 2020 20:42:30 -0400 Received: from mga14.intel.com ([192.55.52.115]:50377 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388830AbgFYAm0 (ORCPT ); Wed, 24 Jun 2020 20:42:26 -0400 IronPort-SDR: dhmuzB9G3PPCPnugLVTyx8IiYAxr7T4jbhFazGzMMwtET9aZHFTlGJMISZXskM5jPriorICLUb b41H7b5IHu0g== X-IronPort-AV: E=McAfee;i="6000,8403,9662"; a="143789085" X-IronPort-AV: E=Sophos;i="5.75,277,1589266800"; d="scan'208";a="143789085" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by fmsmga103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 Jun 2020 17:42:25 -0700 IronPort-SDR: zdjQKndy7Dp+7g0lGPf/NZ03uqInuOzQUle0mkWa3LpVSznuEb917yLqMuNNWvUk7Nyaf2OOAV IGQ/cIynfLxg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.75,277,1589266800"; d="scan'208";a="265219337" Received: from djiang5-mobl1.amr.corp.intel.com (HELO [10.251.31.242]) ([10.251.31.242]) by fmsmga008.fm.intel.com with ESMTP; 24 Jun 2020 17:42:24 -0700 Subject: Re: DMA Engine: Transfer From Userspace To: Vinod Koul Cc: Federico Vaga , Dan Williams , dmaengine@vger.kernel.org, linux-kernel@vger.kernel.org, "Kumar, Sanjay K" , "Luck, Tony" References: <5614531.lOV4Wx5bFT@harkonnen> <20200621072457.GA2324254@vkoul-mobl> From: Dave Jiang Message-ID: <581f1761-e582-c770-169a-ee3374baf25c@intel.com> Date: Wed, 24 Jun 2020 17:42:24 -0700 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.9.0 MIME-Version: 1.0 In-Reply-To: <20200621072457.GA2324254@vkoul-mobl> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 7bit Sender: dmaengine-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: dmaengine@vger.kernel.org On 6/21/2020 12:24 AM, Vinod Koul wrote: > On 19-06-20, 16:31, Dave Jiang wrote: >> >> >> On 6/19/2020 3:47 PM, Federico Vaga wrote: >>> Hello, >>> >>> is there the possibility of using a DMA engine channel from userspace? >>> >>> Something like: >>> - configure DMA using ioctl() (or whatever configuration mechanism) >>> - read() or write() to trigger the transfer >>> >> >> I may have supposedly promised Vinod to look into possibly providing >> something like this in the future. But I have not gotten around to do that >> yet. Currently, no such support. > > And I do still have serious reservations about this topic :) Opening up > userspace access to DMA does not sound very great from security point of > view. What about doing it with DMA engine that supports PASID? That way the user can really only trash its own address space and kernel is protected. > > Federico, what use case do you have in mind? > > We should keep in mind dmaengine is an in-kernel interface providing > services to various subsystems, so you go thru the respective subsystem > kernel interface (network, display, spi, audio etc..) which would in > turn use dmaengine. >