Re: [RFC PATCH 0/7] A General Accelerator Framework, WarpDrive

[Kenneth Lee]

On Thu, Aug 02, 2018 at 04:36:52AM +0000, Tian, Kevin wrote:
> Date: Thu, 2 Aug 2018 04:36:52 +0000
> From: "Tian, Kevin" <kevin.tian@xxxxxxxxx>
> To: Kenneth Lee <liguozhu@xxxxxxxxxxxxx>
> CC: Kenneth Lee <nek.in.cn@xxxxxxxxx>, Herbert Xu
>  <herbert@xxxxxxxxxxxxxxxxxxx>, "kvm@xxxxxxxxxxxxxxx"
>  <kvm@xxxxxxxxxxxxxxx>, Jonathan Corbet <corbet@xxxxxxx>, Greg
>  Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>, "linux-doc@xxxxxxxxxxxxxxx"
>  <linux-doc@xxxxxxxxxxxxxxx>, "Kumar, Sanjay K" <sanjay.k.kumar@xxxxxxxxx>,
>  Hao Fang <fanghao11@xxxxxxxxxx>, "iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx"
>  <iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx>, "linux-kernel@xxxxxxxxxxxxxxx"
>  <linux-kernel@xxxxxxxxxxxxxxx>, "linuxarm@xxxxxxxxxx"
>  <linuxarm@xxxxxxxxxx>, Alex Williamson <alex.williamson@xxxxxxxxxx>,
>  Thomas Gleixner <tglx@xxxxxxxxxxxxx>, "linux-crypto@xxxxxxxxxxxxxxx"
>  <linux-crypto@xxxxxxxxxxxxxxx>, Philippe Ombredanne
>  <pombredanne@xxxxxxxx>, Zaibo Xu <xuzaibo@xxxxxxxxxx>, "David S . Miller"
>  <davem@xxxxxxxxxxxxx>, "linux-accelerators@xxxxxxxxxxxxxxxx"
>  <linux-accelerators@xxxxxxxxxxxxxxxx>
> Subject: RE: [RFC PATCH 0/7] A General Accelerator Framework, WarpDrive
> Message-ID: <AADFC41AFE54684AB9EE6CBC0274A5D19129105A@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>
> 
> > From: Kenneth Lee
> > Sent: Thursday, August 2, 2018 11:40 AM
> > 
> > On Thu, Aug 02, 2018 at 02:59:33AM +0000, Tian, Kevin wrote:
> > > > From: Kenneth Lee
> > > > Sent: Wednesday, August 1, 2018 6:22 PM
> > > >
> > > > From: Kenneth Lee <liguozhu@xxxxxxxxxxxxx>
> > > >
> > > > WarpDrive is an accelerator framework to expose the hardware
> > capabilities
> > > > directly to the user space. It makes use of the exist vfio and vfio-mdev
> > > > facilities. So the user application can send request and DMA to the
> > > > hardware without interaction with the kernel. This remove the latency
> > > > of syscall and context switch.
> > > >
> > > > The patchset contains documents for the detail. Please refer to it for
> > more
> > > > information.
> > > >
> > > > This patchset is intended to be used with Jean Philippe Brucker's SVA
> > > > patch [1] (Which is also in RFC stage). But it is not mandatory. This
> > > > patchset is tested in the latest mainline kernel without the SVA patches.
> > > > So it support only one process for each accelerator.
> > >
> > > If no sharing, then why not just assigning the whole parent device to
> > > the process? IMO if SVA usage is the clear goal of your series, it
> > > might be made clearly so then Jean's series is mandatory dependency...
> > >
> > 
> > We don't know how SVA will be finally. But the feature, "make use of
> > per-PASID/substream ID IOMMU page table", should be able to be enabled
> > in the
> > kernel. So we don't want to enforce it here. After we have this serial ready,
> > it
> > can be hooked to any implementation.
> 
> "any" or "only queue-based" implementation? some devices may not
> have queue concept, e.g. GPU.

Here, "any implementation" refer to the "per PASID page table" implementatin:)

> 
> > 
> > Further more, even without "per-PASID IOMMU page table", this series has
> > its
> > value. It is not simply dedicate the whole device to the process. It "shares"
> > the device with the kernel driver. So you can support crypto and a user
> > application at the same time.
> 
> OK.
> 
> Thanks
> Kevin

-- 
			-Kenneth(Hisilicon)

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