[PATCH v4 0/2] riscv: Optimize bitops with Zbb extension

[Xiao Wang]

Bitops optimization with specialized instructions is common practice in
popular ISAs, this patch set uses RISC-V Zbb extension to optimize four
bitops: __ffs, __fls, ffs and fls.

The first patch rearranges the content in hwcap.h and cpufeature.h, it helps
to avoid a cyclic header including issue for patch 2.

The second patch leverages the alternative mechanism to dynamically apply
this optimization.

Thanks,
Xiao

v4:
- Simplify the asm code in ffs() and fls() by moving general logic into C
  implementation. (Charlie)
- Add a comment to decorating the large #ifdef block. (Charlie)
- Link to v3: https://lore.kernel.org/all/20230926094655.3102758-1-xiao.w.wang@xxxxxxxxx/

v3:
- Fix riscv32 build issue reported by kernel test robot. V3 changes "hwcap.h" to
  "cpufeature.h" for files where cpu feature detection APIs are used. (Yujie)
- Link to v2: https://lore.kernel.org/all/20230920074653.2509631-1-xiao.w.wang@xxxxxxxxx/

v2:
- Remove the "EFI_" prefix from macro name "EFI_NO_ALTERNATIVE" to make it
  generic. (Ard)
- patch-1 is added, it's based on "RISC-V: Enable cbo.zero in usermode". (Andrew)
- Link to v1: https://lore.kernel.org/all/20230806024715.3061589-1-xiao.w.wang@xxxxxxxxx/

Xiao Wang (2):
  riscv: Rearrange hwcap.h and cpufeature.h
  riscv: Optimize bitops with Zbb extension

 arch/riscv/include/asm/bitops.h       | 255 +++++++++++++++++++++++++-
 arch/riscv/include/asm/cpufeature.h   |  83 +++++++++
 arch/riscv/include/asm/elf.h          |   2 +-
 arch/riscv/include/asm/hwcap.h        |  91 ---------
 arch/riscv/include/asm/pgtable.h      |   1 +
 arch/riscv/include/asm/switch_to.h    |   2 +-
 arch/riscv/include/asm/vector.h       |   2 +-
 arch/riscv/kvm/aia.c                  |   2 +-
 arch/riscv/kvm/main.c                 |   2 +-
 arch/riscv/kvm/tlb.c                  |   2 +-
 arch/riscv/kvm/vcpu_fp.c              |   2 +-
 arch/riscv/kvm/vcpu_onereg.c          |   2 +-
 arch/riscv/kvm/vcpu_vector.c          |   2 +-
 drivers/bitopstest/Kconfig            |   1 +
 drivers/clocksource/timer-riscv.c     |   2 +-
 drivers/firmware/efi/libstub/Makefile |   2 +-
 drivers/perf/riscv_pmu_sbi.c          |   2 +-
 17 files changed, 349 insertions(+), 106 deletions(-)

-- 
2.25.1