Re: [RFCv2 PATCH 0/7] A General Accelerator Framework, WarpDrive

[Kenneth Lee]

On Mon, Sep 03, 2018 at 10:32:16AM +0800, Lu Baolu wrote:
> Date: Mon, 3 Sep 2018 10:32:16 +0800
> From: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> To: Kenneth Lee <nek.in.cn@xxxxxxxxx>, Jonathan Corbet <corbet@xxxxxxx>,
>  Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>, "David S . Miller"
>  <davem@xxxxxxxxxxxxx>, Joerg Roedel <joro@xxxxxxxxxx>, Alex Williamson
>  <alex.williamson@xxxxxxxxxx>, Kenneth Lee <liguozhu@xxxxxxxxxxxxx>, Hao
>  Fang <fanghao11@xxxxxxxxxx>, Zhou Wang <wangzhou1@xxxxxxxxxxxxx>, Zaibo Xu
>  <xuzaibo@xxxxxxxxxx>, Philippe Ombredanne <pombredanne@xxxxxxxx>, Greg
>  Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>, Thomas Gleixner
>  <tglx@xxxxxxxxxxxxx>, linux-doc@xxxxxxxxxxxxxxx,
>  linux-kernel@xxxxxxxxxxxxxxx, linux-crypto@xxxxxxxxxxxxxxx,
>  iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx, kvm@xxxxxxxxxxxxxxx,
>  linux-accelerators@xxxxxxxxxxxxxxxx, Sanjay Kumar
>  <sanjay.k.kumar@xxxxxxxxx>
> CC: baolu.lu@xxxxxxxxxxxxxxx, linuxarm@xxxxxxxxxx
> Subject: Re: [RFCv2 PATCH 0/7] A General Accelerator Framework, WarpDrive
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> 
> Hi,
> 
> On 09/03/2018 08:51 AM, Kenneth Lee wrote:
> >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 removes the latency
> >of syscall.
> >
> >WarpDrive is the name for the whole framework. The component in kernel
> >is called SDMDEV, Share Domain Mediated Device. Driver driver exposes its
> >hardware resource by registering to SDMDEV as a VFIO-Mdev. So the user
> >library of WarpDrive can access it via VFIO interface.
> >
> >The patchset contains document 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 enables not only IO side page fault, but also PASID
> >support to IOMMU and VFIO.
> >
> >With these features, WarpDrive can support non-pinned memory and
> >multi-process in the same accelerator device.  We tested it in our SoC
> >integrated Accelerator (board ID: D06, Chip ID: HIP08). A reference work
> >tree can be found here: [2].
> >
> >But it is not mandatory. This patchset is tested in the latest mainline
> >kernel without the SVA patches.  So it supports only one process for each
> >accelerator.
> >
> >We have noticed the IOMMU aware mdev RFC announced recently [3].
> >
> >The IOMMU aware mdev has similar idea but different intention comparing to
> >WarpDrive. It intends to dedicate part of the hardware resource to a VM.
> >And the design is supposed to be used with Scalable I/O Virtualization.
> >While sdmdev is intended to share the hardware resource with a big amount
> >of processes.  It just requires the hardware supporting address
> >translation per process (PCIE's PASID or ARM SMMU's substream ID).
> >
> >But we don't see serious confliction on both design. We believe they can be
> >normalized as one.
> >
> >The patch 1 is document of the framework. The patch 2 and 3 add sdmdev
> >support. The patch 4, 5 and 6 is drivers for Hislicon's ZIP Accelerator
> >which is registered to both crypto and warpdrive(sdmdev) and can be
> >used from kernel or user space at the same time. The patch 7 is a user
> >space sample demonstrating how WarpDrive works.
> >
> >
> >Change History:
> >V2 changed from V1:
> >	1. Change kernel framework name from SPIMDEV (Share Parent IOMMU
> >	   Mdev) to SDMDEV (Share Domain Mdev).
> >	2. Allocate Hardware Resource when a new mdev is created (While
> >	   it is allocated when the mdev is openned)
> >	3. Unmap pages from the shared domain when the sdmdev iommu group is
> >	   detached. (This procedure is necessary, but missed in V1)
> >	4. Update document accordingly.
> >	5. Rebase to the latest kernel (4.19.0-rc1)
> >	
> >	According the review comment on RFCv1, We did try to use dma-buf
> >	as back end of WarpDrive. It can work properly with the current
> >	solution [4], but it cannot make use of process's
> >	own memory address space directly. This is important to many
> >	acceleration scenario. So dma-buf will be taken as a backup
> >	alternative for noiommu scenario, it will be added in the future
> >	version.
> >
> >
> >Refernces:
> >[1] https://www.spinics.net/lists/kernel/msg2651481.html
> >[2] https://github.com/Kenneth-Lee/linux-kernel-warpdrive/tree/warpdrive-sva-v0.5
> >[3] https://lkml.org/lkml/2018/7/22/34
> 
> Please refer to the latest version posted here for discussion.
> 
> https://lkml.org/lkml/2018/8/30/107

Sure. Thank you.

> 
> Best regards,
> Lu Baolu

-- 
			-Kenneth(Hisilicon)

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