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=-2.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,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 B3E9AC3A59E for ; Mon, 26 Aug 2019 04:29:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 824272190F for ; Mon, 26 Aug 2019 04:29:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1566793755; bh=EQP40mviagoanbkf4TmOFcFWN9aA6tPpZUAKg/ROjCI=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=rfOrJWQ+DJJiJ22+K11Q7ZTLzw7t+XMdmO1i7AN8ODoI25SDJ3rKIKavXHwS9H1AW sdHMELT9TiiUuzOosL3ZXvIqbgv/WABRlmldL8PqMgm0wHGZGv5Icz65Nrk3bDp31t 62mLaR2RWva7S2rXIRglCxboieOJOFWcGUWxVfQ8= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729697AbfHZE3O (ORCPT ); Mon, 26 Aug 2019 00:29:14 -0400 Received: from mail.kernel.org ([198.145.29.99]:55124 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725270AbfHZE3O (ORCPT ); Mon, 26 Aug 2019 00:29:14 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 983C62173E; Mon, 26 Aug 2019 04:29:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1566793753; bh=EQP40mviagoanbkf4TmOFcFWN9aA6tPpZUAKg/ROjCI=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=NIs8t17yyjsbbIibwB+K02pUYQzsJk6jGL8BVROx9lG4gVQjJIjTcZ6QtocWM0nwC H/ex1aWHhkwrpImxcXmlx4dhsGC2yQmWXKUrLCxHuA6UFqX1eXUrxAt6l5xjpL39dr ET9eiJLj/9UjLW8101iJrFygcQHOe7gyLtK6+pew= Date: Mon, 26 Aug 2019 06:29:10 +0200 From: Greg Kroah-Hartman To: Kenneth Lee Cc: zhangfei , Arnd Bergmann , linux-accelerators@lists.ozlabs.org, linux-kernel@vger.kernel.org, Zaibo Xu , Zhou Wang Subject: Re: [PATCH 2/2] uacce: add uacce module Message-ID: <20190826042910.GA26547@kroah.com> References: <1565775265-21212-1-git-send-email-zhangfei.gao@linaro.org> <1565775265-21212-3-git-send-email-zhangfei.gao@linaro.org> <20190815141351.GD23267@kroah.com> <6daab785-a8f9-684e-eb71-7a81604d3bb0@linaro.org> <20190820165947.GC3736@kroah.com> <5d5cf0fc.1c69fb81.ec57f.b853SMTPIN_ADDED_BROKEN@mx.google.com> <20190821091709.GA22914@kroah.com> <20190821160542.GA14760@kroah.com> <20190826041042.GB27955@Turing-Arch-b> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20190826041042.GB27955@Turing-Arch-b> User-Agent: Mutt/1.12.1 (2019-06-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Aug 26, 2019 at 12:10:42PM +0800, Kenneth Lee wrote: > On Wed, Aug 21, 2019 at 09:05:42AM -0700, Greg Kroah-Hartman wrote: > > Date: Wed, 21 Aug 2019 09:05:42 -0700 > > From: Greg Kroah-Hartman > > To: zhangfei > > CC: Arnd Bergmann , linux-accelerators@lists.ozlabs.org, > > linux-kernel@vger.kernel.org, Kenneth Lee , Zaibo > > Xu , Zhou Wang > > Subject: Re: [PATCH 2/2] uacce: add uacce module > > User-Agent: Mutt/1.12.1 (2019-06-15) > > Message-ID: <20190821160542.GA14760@kroah.com> > > > > On Wed, Aug 21, 2019 at 10:30:22PM +0800, zhangfei wrote: > > > > > > > > > On 2019/8/21 下午5:17, Greg Kroah-Hartman wrote: > > > > On Wed, Aug 21, 2019 at 03:21:18PM +0800, zhangfei.gao@foxmail.com wrote: > > > > > Hi, Greg > > > > > > > > > > On 2019/8/21 上午12:59, Greg Kroah-Hartman wrote: > > > > > > On Tue, Aug 20, 2019 at 09:08:55PM +0800, zhangfei wrote: > > > > > > > On 2019/8/15 下午10:13, Greg Kroah-Hartman wrote: > > > > > > > > On Wed, Aug 14, 2019 at 05:34:25PM +0800, Zhangfei Gao wrote: > > > > > > > > > +int uacce_register(struct uacce *uacce) > > > > > > > > > +{ > > > > > > > > > + int ret; > > > > > > > > > + > > > > > > > > > + if (!uacce->pdev) { > > > > > > > > > + pr_debug("uacce parent device not set\n"); > > > > > > > > > + return -ENODEV; > > > > > > > > > + } > > > > > > > > > + > > > > > > > > > + if (uacce->flags & UACCE_DEV_NOIOMMU) { > > > > > > > > > + add_taint(TAINT_CRAP, LOCKDEP_STILL_OK); > > > > > > > > > + dev_warn(uacce->pdev, > > > > > > > > > + "Register to noiommu mode, which export kernel data to user space and may vulnerable to attack"); > > > > > > > > > + } > > > > > > > > THat is odd, why even offer this feature then if it is a major issue? > > > > > > > UACCE_DEV_NOIOMMU maybe confusing here. > > > > > > > > > > > > > > In this mode, app use ioctl to get dma_handle from dma_alloc_coherent. > > > > > > That's odd, why not use the other default apis to do that? > > > > > > > > > > > > > It does not matter iommu is enabled or not. > > > > > > > In case iommu is disabled, it maybe dangerous to kernel, so we added warning here, is it required? > > > > > > You should use the other documentated apis for this, don't create your > > > > > > own. > > > > > I am sorry, not understand here. > > > > > Do you mean there is a standard ioctl or standard api in user space, it can > > > > > get dma_handle from dma_alloc_coherent from kernel? > > > > There should be a standard way to get such a handle from userspace > > > > today. Isn't that what the ion interface does? DRM also does this, as > > > > does UIO I think. > > > Thanks Greg, > > > Still not find it, will do more search. > > > But this may introduce dependency in our lib, like depend on ion? > > > > Do you have a spec somewhere that shows exactly what you are trying to > > > > do here, along with example userspace code? It's hard to determine it > > > > given you only have one "half" of the code here and no users of the apis > > > > you are creating. > > > > > > > The purpose is doing dma in user space. > > > > Oh no, please no. Are you _SURE_ you want to do this? > > > > Again, look at how ION does this and how the DMAbuff stuff is replacing > > it. Use that api please instead, otherwise you will get it wrong and we > > don't want to duplicate efforts. > > > > thanks, > > > > greg k-h > > Dear Greg. I wrote a blog to explain the intention of WarpDrive here: > https://zhuanlan.zhihu.com/p/79680889. Putting that information into the changelog and kernel documentation is a much better idea than putting it there. > Sharing data is not our intention, Sharing address is. NOIOMMU mode is just a > temporary solution to let some hardware which does not care the security issue > to try WarpDrive for the first step. Some user do not care this much in embedded > scenario. We saw VFIO use the same model so we also want to make a try. If you > insist this is risky, we can remove it. Why not just use vfio then? And yes, for now, please remove it, if you are not requiring it. thanks, greg k-h