[PATCH 0/3] unified way to use static key and optimize pgtable_l4_enabled

[Jisheng Zhang]

Currently, riscv has several features why may not be supported on all
riscv platforms, for example, FPU, SV48 and so on. To support unified
kernel Image style, we need to check whether the feature is suportted
or not. If the check sits at hot code path, then performance will be
impacted a lot. static key can be used to solve the issue. In the
past FPU support has been converted to use static key mechanism. I
believe we will have similar cases in the future. For example, the
SV48 support can take advantage of static key[1].

patch1 introduces an unified mechanism to use static key for riscv cpu
features.
patch2 converts has_cpu() to use the mechanism.
patch3 uses the mechanism to optimize pgtable_l4_enabled.

[1] http://lists.infradead.org/pipermail/linux-riscv/2021-December/011164.html

Jisheng Zhang (3):
  riscv: introduce unified static key mechanism for CPU features
  riscv: replace has_fpu() with system_supports_fpu()
  riscv: convert pgtable_l4_enabled to static key

 arch/riscv/Makefile                 |   3 +
 arch/riscv/include/asm/cpufeature.h | 105 ++++++++++++++++++++++++++++
 arch/riscv/include/asm/pgalloc.h    |   8 +--
 arch/riscv/include/asm/pgtable-64.h |  21 +++---
 arch/riscv/include/asm/pgtable.h    |   3 +-
 arch/riscv/include/asm/switch_to.h  |   9 +--
 arch/riscv/kernel/cpu.c             |   2 +-
 arch/riscv/kernel/cpufeature.c      |  29 ++++++--
 arch/riscv/kernel/process.c         |   2 +-
 arch/riscv/kernel/signal.c          |   4 +-
 arch/riscv/mm/init.c                |  23 +++---
 arch/riscv/mm/kasan_init.c          |   6 +-
 arch/riscv/tools/Makefile           |  22 ++++++
 arch/riscv/tools/cpucaps            |   6 ++
 arch/riscv/tools/gen-cpucaps.awk    |  40 +++++++++++
 15 files changed, 234 insertions(+), 49 deletions(-)
 create mode 100644 arch/riscv/include/asm/cpufeature.h
 create mode 100644 arch/riscv/tools/Makefile
 create mode 100644 arch/riscv/tools/cpucaps
 create mode 100755 arch/riscv/tools/gen-cpucaps.awk

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2.34.1