[PATCH v2 0/7] riscv: convert bottom half of exception handling to C

[Jisheng Zhang <jszhang@kernel.org>]

For readability, maintainability and future scalability, convert the
bottom half of the exception handling to C.

During the conversion, I found Anton fixed a performance issue[1]
and my patches will touch the same exception asm code, so this series
is applied against Anton's patch.

patch1 and patch2 are cleanup patches.
patch3~patch7 do the conversion and some cleanup/optimization
after conversion.

Mostly the assembly code is converted to C in a relatively
straightforward manner.

However, there are two modifications I need to mention:

1. the cause I.E the CSR_CAUSE value is passed to do_traps() via. 2nd
param, do_traps() doesn't get it from pt_regs because this way an extra
memory load is needed, the exception handling sits in hot code path,
every instruction matters.

2.To cope with SIFIVE_CIP_453 errata, it looks like we don't need
alternative mechanism any more after the asm->c conversion. Just
replace the excp_vect_table two entries.

Link: https://lore.kernel.org/linux-riscv/20240607061335.2197383-1-cyrilbur@tenstorrent.com/ [1]

since v1:
 - add two clean up patches
 - remove the two patches which fix imbalance in RAS, instead, explicitly
   mark this series is applied against one of them.
 - save cause in pt_regs prior to calling do_traps()
 - do more clean up and optimization after the asm->c conversion:
   staticalize and mark do_irq() as __always_inline.

Jisheng Zhang (7):
  riscv: traps: staticalize handle_break()
  riscv: traps: remove __visible annotation
  riscv: convert bottom half of exception handling to C
  riscv: errata: remove ALT_INSN_FAULT and ALT_PAGE_FAULT
  riscv: errata: sifive: remove NOMMU handling
  riscv: staticalize and remove asmlinkage from updated functions
  riscv: traps: mark do_irq() as __always_inline

 arch/riscv/errata/sifive/errata.c         | 25 +++++++---
 arch/riscv/errata/sifive/errata_cip_453.S |  4 --
 arch/riscv/include/asm/asm-prototypes.h   | 20 +-------
 arch/riscv/include/asm/entry-common.h     |  1 -
 arch/riscv/include/asm/errata_list.h      | 21 ++-------
 arch/riscv/kernel/entry.S                 | 57 +----------------------
 arch/riscv/kernel/kernel_mode_vector.c    |  2 +-
 arch/riscv/kernel/traps.c                 | 55 ++++++++++++++++++----
 8 files changed, 73 insertions(+), 112 deletions(-)

-- 
2.43.0


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