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ISA Introduction (csky)

what's the meaning of a new arch for linux

Guo Ren

<guoren@kernel.org>

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T-HEAD�XuanTie CPU Series

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C-SKY Upstream�

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2018-10-29 08:25:00 -0700

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?h=master&id=ac435075892e3e651c667b4a9f2267cf3ef1d5a2

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A little regret (missing comment)

2018-10-30 00:22:45 +0800�https://lore.kernel.org/lkml/20181029162243.GA988@guoren-Inspiron-7460/

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Our jobs:

CPU

ISA

Linux Directory

610 (no sale)

MCORE 32 (Modified)

linux/arch/csky/abiv1

807/810/860

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C-SKY 32

linux/arch/csky/abiv2

910

RISC-V 64

linux/arch/riscv

  • Now we need take care of 3 ISAs with 5 cores
  • Kernel, glibc, uclibc-ng, buildroot, elfutils, strace, greenlet, perf, systemtap ...
  • https://gitlab.com/c-sky/buildroot/pipelines

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Kernel Version

  • Linux-next
  • Linux-4.19
  • Linux-4.9

Quick Start:

https://github.com/c-sky/buildroot

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Boot

code:

Our Principle:

  • Easy to use
  • Easy to understand

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Use KSEG for 32bit CPU

  • KSEG is an ancient technology from mips.�https://johnloomis.org/microchip/pic32/memory/memory.html
  • We also have KSEG0, KSEG1, but they are used mapping 0-1GB cached memory (No IO map) to reduce unnecessary TLB miss
  • We also provide base regs to support any start physical address (512MB align)
  • Why we use KSEG ?
    • It’s cheaper than middle level page mapping for hardware
    • It’s more efficient than MMU for hardware
    • Hugetlbfs and THP are useless in 32b system with small memory (personal opinion)

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Current State:

  • Highmem
  • SMP
    • cpu hotplug
    • 1024 sources root interrupt controller
    • support both percpu-irq and comm-irq in one driver
  • Ftrace, Dynamic Ftrace
  • Strace
  • Perf (Hardware PMU supported with perf record)

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Recent Plan:

  • SystemTap (kprobe/uprobe)
  • VDSO Optimization
  • BPF JIT
  • Trace with “perf record -e thead_pt/*”
  • IOMMU

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$6 Linux Development Board with C-SKY ISA

https://c-sky.github.io/docs/gx6605s.html�

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Thank you

Actually, I don’t know what’s the meaning of a new arch for linux :P

�But we’ll continue improving the arch - day by day, patch by patch

Just continue working & keep changing

T-HEAD