On 5/3/20 7:21 am, Haren Myneni wrote:
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. Tested these patches with NX-GZIP support and will be posting this series soon. Patches 1 & 2: Define alloc IRQ and get port address per chip which are needed to alloc IRQ per VAS instance. Patch 3: Define nx_fault_stamp on which NX writes fault status for the fault CRB Patch 4: Alloc and setup IRQ and trigger port address for each VAS instance Patch 5: Setup fault window per each VAS instance. This window is used for NX to paste fault CRB in FIFO. Patches 6 & 7: Setup threaded IRQ per VAS and register NX with fault window ID and port number for each send window so that NX paste fault CRB in this window. Patch 8: Reference to pid and mm so that pid is not used until window closed. Needed for multi thread application where child can open a window and can be used by parent later. Patches 9 and 10: Process CRBs from fault FIFO and notify tasks by updating CSB or through signals. Patches 11 and 12: Return credits for send and fault windows after handling faults. Patch 14:Fix closing send window after all credits are returned. This issue happens only for user space requests. No page faults on kernel request buffer.
This series adds a bunch of sparse warnings - it would be great if you could take a look.
https://openpower.xyz/job/snowpatch/job/snowpatch-linux-sparse/16052//artifact/linux/report.txt -- Andrew Donnellan OzLabs, ADL Canberra a...@linux.ibm.com IBM Australia Limited