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=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,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 7BE75C3A5A3 for ; Tue, 27 Aug 2019 18:48:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4470921883 for ; Tue, 27 Aug 2019 18:48:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1566931709; bh=ZiCAIffTdsF1bgCrGidfjVki+oHlbaJt6PVAuhhR8cY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=107CESiAmT9ts4Mi2vY1KOq6uG8ED9f8bZZqYuxp1m3Bm6bsjvjYjrYvONOkyqd6Z T9rE/NHpTm4MUiTejaiMfLlRZu1S4McRz8ufQE54bKbyoI7y4xyu3nBOvNgIqUmpTQ uQTexR+J2JBlgdKd47en6RdyATop14MX5uD7TtPY= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730808AbfH0Ss2 (ORCPT ); Tue, 27 Aug 2019 14:48:28 -0400 Received: from mail.kernel.org ([198.145.29.99]:46036 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729903AbfH0Ss1 (ORCPT ); Tue, 27 Aug 2019 14:48:27 -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 D621720644; Tue, 27 Aug 2019 18:48:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1566931706; bh=ZiCAIffTdsF1bgCrGidfjVki+oHlbaJt6PVAuhhR8cY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=CZi2h0edM4wr9EPiY0R5BM8VzmhFkHaiLiRzetS0zchYepWLldK/VEo3BPuK/gfE0 wDya2tEpSrWQVMv07h8S0uxjBLGHT9+epEYWnlDfpt4isX813Bq9MgKZ4q4UPXPteZ FBJxeaoHjnaqMifwWE27dsKIXrrRndSRvOI3waDg= Date: Tue, 27 Aug 2019 20:48:23 +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: <20190827184823.GC2987@kroah.com> References: <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> <20190826042910.GA26547@kroah.com> <20190827114208.GB116872@Turing-Arch-b> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20190827114208.GB116872@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 Tue, Aug 27, 2019 at 07:42:08PM +0800, Kenneth Lee wrote: > On Mon, Aug 26, 2019 at 06:29:10AM +0200, Greg Kroah-Hartman wrote: > > 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 > > User-Agent: Mutt/1.12.1 (2019-06-15) > > Message-ID: <20190826042910.GA26547@kroah.com> > > > > 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. > > Yes, will do. Thank you. > > > > > > 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? > > We tried that in previous patches. But it needs to create unnecessary mdev to > fulfill the requirement. So we discard it after the discussion in lkml. Any pointers to that discussion? thanks, greg k-h