Hi! > WarpDrive is a common user space accelerator framework. Its main component > in Kernel is called spimdev, Share Parent IOMMU Mediated Device. It exposes spimdev is really unfortunate name. It looks like it has something to do with SPI, but it does not. > +++ b/Documentation/warpdrive/warpdrive.rst > @@ -0,0 +1,153 @@ > +Introduction of WarpDrive > +========================= > + > +*WarpDrive* is a general accelerator framework built on top of vfio. > +It can be taken as a light weight virtual function, which you can use without > +*SR-IOV* like facility and can be shared among multiple processes. > + > +It can be used as the quick channel for accelerators, network adaptors or > +other hardware in user space. It can make some implementation simpler. E.g. > +you can reuse most of the *netdev* driver and just share some ring buffer to > +the user space driver for *DPDK* or *ODP*. Or you can combine the RSA > +accelerator with the *netdev* in the user space as a Web reversed proxy, etc. What is DPDK? ODP? > +How does it work > +================ > + > +*WarpDrive* takes the Hardware Accelerator as a heterogeneous processor which > +can share some load for the CPU: > + > +.. image:: wd.svg > + :alt: This is a .svg image, if your browser cannot show it, > + try to download and view it locally > + > +So it provides the capability to the user application to: > + > +1. Send request to the hardware > +2. Share memory with the application and other accelerators > + > +These requirements can be fulfilled by VFIO if the accelerator can serve each > +application with a separated Virtual Function. But a *SR-IOV* like VF (we will > +call it *HVF* hereinafter) design is too heavy for the accelerator which > +service thousands of processes. VFIO? VF? HVF? Also "gup" might be worth spelling out. > +References > +========== > +.. [1] Accroding to the comment in in mm/gup.c, The *gup* is only safe within > + a syscall. Because it can only keep the physical memory in place > + without making sure the VMA will always point to it. Maybe we should > + raise the VM_PINNED patchset (see > + https://lists.gt.net/linux/kernel/1931993) again to solve this probl I went through the docs, but I still don't know what it does. Pavel
