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

[Tian, Kevin]

> 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.

> 
> 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