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 <gre...@linuxfoundation.org> > > To: zhangfei <zhangfei....@linaro.org> > > CC: Arnd Bergmann <a...@arndb.de>, linux-accelerat...@lists.ozlabs.org, > > linux-kernel@vger.kernel.org, Kenneth Lee <liguo...@hisilicon.com>, Zaibo > > Xu <xuza...@huawei.com>, Zhou Wang <wangzh...@hisilicon.com> > > Subject: Re: [PATCH 2/2] uacce: add uacce module > > User-Agent: Mutt/1.12.1 (2019-06-15) > > Message-ID: <20190821160542.ga14...@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....@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