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

[Lu Baolu]

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

Best regards,
Lu Baolu