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 <gre...@linuxfoundation.org>
> > To: Kenneth Lee <liguo...@hisilicon.com>
> > CC: zhangfei <zhangfei....@linaro.org>, Arnd Bergmann <a...@arndb.de>,
> > linux-accelerat...@lists.ozlabs.org, linux-kernel@vger.kernel.org, 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: <20190826042910.ga26...@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 <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.
>
> 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
