linux-kernel - Re: [PATCH 2/2] uacce: add uacce module

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Message-ID: <20190823173603.00001b3d@huawei.com>
Date:   Fri, 23 Aug 2019 17:36:03 +0100
From:   Jonathan Cameron <jonathan.cameron@...wei.com>
To:     zhangfei <zhangfei.gao@...aro.org>
CC:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Arnd Bergmann <arnd@...db.de>, Zaibo Xu <xuzaibo@...wei.com>,
        <linux-kernel@...r.kernel.org>,
        Zhou Wang <wangzhou1@...ilicon.com>,
        "Kenneth Lee" <liguozhu@...ilicon.com>,
        <linux-accelerators@...ts.ozlabs.org>
Subject: Re: [PATCH 2/2] uacce: add uacce module

On Fri, 23 Aug 2019 17:21:33 +0800
zhangfei <zhangfei.gao@...aro.org> wrote:

> Hi, Jonathan
Hi zhangfei,

> 
> Thanks for your careful review and good suggestion.
> Sorry for late response, I am checking one detail.

I have reviews on patches from years ago that I still haven't replied to ;)

> 
> On 2019/8/16 上午12:54, Jonathan Cameron wrote:
> > On Wed, 14 Aug 2019 17:34:25 +0800
> > Zhangfei Gao <zhangfei.gao@...aro.org> wrote:
> >  
> >> From: Kenneth Lee <liguozhu@...ilicon.com>
> >>
> >> Uacce is the kernel component to support WarpDrive accelerator
> >> framework. It provides register/unregister interface for device drivers
> >> to expose their hardware resource to the user space. The resource is
> >> taken as "queue" in WarpDrive.  
> > It's a bit confusing to have both the term UACCE and WarpDrive in here.
> > I'd just use the uacce name in all comments etc.  
> Yes, make sense
> >  
> >> Uacce create a chrdev for every registration, the queue is allocated to
> >> the process when the chrdev is opened. Then the process can access the
> >> hardware resource by interact with the queue file. By mmap the queue
> >> file space to user space, the process can directly put requests to the
> >> hardware without syscall to the kernel space.
> >>
> >> Uacce also manages unify addresses between the hardware and user space
> >> of the process. So they can share the same virtual address in the
> >> communication.
> >>
> >> Signed-off-by: Kenneth Lee <liguozhu@...ilicon.com>
> >> Signed-off-by: Zaibo Xu <xuzaibo@...wei.com>
> >> Signed-off-by: Zhou Wang <wangzhou1@...ilicon.com>
> >> Signed-off-by: Zhangfei Gao <zhangfei.gao@...aro.org>  
> > I would strip this back to which ever case is of most interest (SVA I guess?)
> > and only think about adding support for the others if necessary at a later date.
> > (or in later patches).  
> Do you mean split the patch and send sva part first?

Either:
1) SVA only in the first series, second series can do other options.
2) Patch N for SVA only, N+1... for other features.

I don't mind which, but I want to be able to see just one case and
review that before taking into account the affect of the more complex cases.


> >> +
> >> +static int uacce_qfr_alloc_pages(struct uacce_qfile_region *qfr)
> >> +{
> >> +	int gfp_mask = GFP_ATOMIC | __GFP_ZERO;  
> > More readable to just have this inline.  
> Yes, all right.
> >  
> >> +	int i, j;
> >> +
...

> >> +static int uacce_set_iommu_domain(struct uacce *uacce)
> >> +{
> >> +	struct iommu_domain *domain;
> >> +	struct iommu_group *group;
> >> +	struct device *dev = uacce->pdev;
> >> +	bool resv_msi;
> >> +	phys_addr_t resv_msi_base = 0;
> >> +	int ret;
> >> +
> >> +	if ((uacce->flags & UACCE_DEV_NOIOMMU) ||
> >> +	    (uacce->flags & UACCE_DEV_PASID))
> >> +		return 0;
> >> +
> >> +	/*
> >> +	 * We don't support multiple register for the same dev in RFC version ,
> >> +	 * will add it in formal version  
> > So this effectively multiple complete uacce interfaces for one device.
> > Is there a known usecase for that?  
> Here is preventing one device with multiple algorithm and register 
> multi-times,
> and without sva, they can not be distinguished.

Isn't that a bug in the device driver?

> >> +	 */
> >> +	ret = class_for_each_device(uacce_class, NULL, uacce->pdev,
> >> +				    uacce_dev_match);
> >> +	if (ret)
> >> +		return ret;
> >> +
> >> +	/* allocate and attach a unmanged domain */

...