RE: [MAINTAINER SUMMIT] User-space requirements for accelerator drivers

Luck, Tony
2021-09-14T15:44:11Z

> d) device has full preempt on all hw blocks, is fully coherent, can
> trigger paging sanely, userspace can submit directly (pipe dream).

Not a pipe dream. Coming soon to a server near you. The Intel "ENQCMD"
instruction can be used from userspace to submit a descriptor to an
accelerator device. ENQCMD picks up the PASID from an MSR during
submission, so the device can ask the iommu to translate virtual addresses
based on the address space of the process that submitted the descriptor.

-Tony