Messages in this thread | | | Subject | Re: [PATCH v10 00/14] powerpc/vas: Page fault handling for user space NX requests | From | Cédric Le Goater <> | Date | Fri, 3 Apr 2020 10:19:40 +0200 |
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On 4/2/20 9:00 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.
How complex would it be to provide a QEMU PowerNV model for the NX and VAS units ? We can stage the different level of support. First would be a simple HW init. I am interested for the XIVE modeling of course.
Thanks,
C.
> > 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 enable patches and posted them as separate > patch series. > > Patch 1: Define alloc IRQ per chip which is needed to alloc IRQ per VAS > instance. > Patch 2: Define nx_fault_stamp on which NX writes fault status for the fault > CRB > Patch 3: Alloc and setup IRQ and trigger port address for each VAS instance > Patches 4 & 5: Setup fault window and register NX per each VAS instance. This > window is used for NX to paste fault CRB in FIFO. > Patch 6: 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 it later. > Patch 7: Setup threaded IRQ handler per VAS > Patch 8: Process CRBs from fault FIFO and notify tasks by updating CSB or > through signals. > Patches 9 & 11: Return credits for send and fault windows after handling > faults. > Patches 10 & 12: Dump FIFO / CRB data and messages for error conditions > Patch 13: Fix closing send window after all credits are returned. This issue > happens only for user space requests. No page faults on kernel > request buffer. > Patch 14: For each process / thread, use mm_context->vas_windows counter to > clear foreign address mapping and disable it. > > Changelog: > > V2: > - Use threaded IRQ instead of own kernel thread handler > - Use pswid instead of user space CSB address to find valid CRB > - Removed unused macros and other changes as suggested by Christoph Hellwig > > V3: > - Rebased to 5.5-rc2 > - Use struct pid * instead of pid_t for vas_window tgid > - Code cleanup as suggested by Christoph Hellwig > > V4: > - Define xive alloc and get IRQ info based on chip ID and use these > functions for IRQ setup per VAS instance. It eliminates skiboot > dependency as suggested by Oliver. > > V5: > - Do not update CSB if the process is exiting (patch8) > > V6: > - Add interrupt handler instead of default one and return IRQ_HANDLED > if the fault handling thread is already in progress. (Patch7) > - Use platform send window ID and CCW[0] bit to find valid CRB in > fault FIFO (Patch7). > - Return fault address to user space in BE and other changes as > suggested by Michael Neuling. (patch8) > - Rebased to 5.6-rc4 > > V7: > - Fixed sparse warnings (patches 4, 9 and 10) > > V8: > - Moved mm_context_remove_copro() before mmdrop() (patch6) > - Moved barrier before csb.flags store and add WARN_ON_ONCE() checks (patch8) > > V9: > - Rebased to 5.6 > - Changes based on Cedric's comments > - Removed "Define xive_native_alloc_get_irq_info()" patch and used > irq_get_handler_data() (patch3) > - Changes based on comments from Nicholas Piggin > - Moved "Taking PID reference" patch before setting VAS fault handler > patch > - Removed mutex_lock/unlock (patch7) > - Other cleanup changes > > V10: > - Include patch to enable and disable CP_ABORT execution using > mm_context->vas_windows counter. > - Remove 'if (txwin)' line which is covered with 'else' before (patch6) > > Haren Myneni (14): > powerpc/xive: Define xive_native_alloc_irq_on_chip() > powerpc/vas: Define nx_fault_stamp in coprocessor_request_block > powerpc/vas: Alloc and setup IRQ and trigger port address > powerpc/vas: Setup fault window per VAS instance > powerpc/vas: Register NX with fault window ID and IRQ port value > powerpc/vas: Take reference to PID and mm for user space windows > powerpc/vas: Setup thread IRQ handler per VAS instance > powerpc/vas: Update CSB and notify process for fault CRBs > powerpc/vas: Return credits after handling fault > powerpc/vas: Print CRB and FIFO values > powerpc/vas: Do not use default credits for receive window > powerpc/vas: Display process stuck message > powerpc/vas: Free send window in VAS instance after credits returned > powerpc: Use mm_context vas_windows counter to issue CP_ABORT > > arch/powerpc/include/asm/book3s/64/mmu.h | 3 + > arch/powerpc/include/asm/icswx.h | 20 +- > arch/powerpc/include/asm/mmu_context.h | 22 ++ > arch/powerpc/include/asm/processor.h | 1 - > arch/powerpc/include/asm/xive.h | 9 +- > arch/powerpc/kernel/process.c | 8 +- > arch/powerpc/platforms/powernv/Makefile | 2 +- > arch/powerpc/platforms/powernv/vas-debug.c | 2 +- > arch/powerpc/platforms/powernv/vas-fault.c | 382 ++++++++++++++++++++++++++++ > arch/powerpc/platforms/powernv/vas-window.c | 202 ++++++++++++++- > arch/powerpc/platforms/powernv/vas.c | 85 ++++++- > arch/powerpc/platforms/powernv/vas.h | 57 ++++- > arch/powerpc/sysdev/xive/native.c | 6 +- > 13 files changed, 767 insertions(+), 32 deletions(-) > create mode 100644 arch/powerpc/platforms/powernv/vas-fault.c >
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