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Merge VAS page fault handling into next
As described by Haren:
On Power9, Virtual Accelerator Switchboard (VAS) allows user space or
kernel to communicate with Nest Accelerator (NX) directly using
COPY/PASTE instructions. NX provides various functionalities such as
compression, encryption and etc. But only compression (842 and GZIP
formats) is supported in Linux kernel on power9.
842 compression driver (drivers/crypto/nx/nx-842-powernv.c) is already
included in Linux. Only GZIP support will be available from user
space.
Applications can issue GZIP compression / decompression requests to NX
with COPY/PASTE instructions. When NX is processing these requests,
can hit fault on the request buffer (not in memory). It issues an
interrupt and pastes fault CRB in fault FIFO. Expects kernel to handle
this fault and return credits for both send and fault windows after
processing.
This patch series adds IRQ and fault window setup, and NX fault
handling:
- Alloc IRQ and trigger port address, and configure IRQ per VAS
instance.
- Set port# for each window to generate an interrupt when noticed
fault.
- Set fault window and FIFO on which NX paste fault CRB.
- Setup IRQ thread fault handler per VAS instance.
- When receiving an interrupt, Read CRBs from fault FIFO and update
coprocessor_status_block (CSB) in the corresponding CRB with
translation failure (CSB_CC_TRANSLATION). After issuing NX
requests, process polls on CSB address. When it sees translation
error, can touch the request buffer to bring the page in to memory
and reissue NX request.
- If copy_to_user fails on user space CSB address, OS sends SEGV
signal.