linux-kernel - Re: [PATCH v2 0/7] riscv: Various text patching improvements

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Date: Wed, 22 May 2024 09:35:38 -0700 (PDT)
From: Palmer Dabbelt <palmer@...belt.com>
To: samuel.holland@...ive.com
CC: Bjorn Topel <bjorn@...osinc.com>, linux-riscv@...ts.infradead.org,
  linux-kernel@...r.kernel.org, samuel.holland@...ive.com, Ard Biesheuvel <ardb@...nel.org>,
  daniel@...earbox.net, jbaron@...mai.com, jpoimboe@...nel.org, peterz@...radead.org,
  rostedt@...dmis.org, bpf@...r.kernel.org
Subject:     Re: [PATCH v2 0/7] riscv: Various text patching improvements

On Wed, 27 Mar 2024 09:04:39 PDT (-0700), samuel.holland@...ive.com wrote:
> Here are a few changes to minimize calls to stop_machine() and
> flush_icache_*() in the various text patching functions, as well as
> to simplify the code.
>
> This series is based on "[PATCH v3 0/2] riscv: fix patching with IPI"[1].
>
> [1]: https://lore.kernel.org/linux-riscv/20240229121056.203419-1-alexghiti@rivosinc.com/
>
> Changes in v2:
>  - Remove unnecessary line wrapping
>  - Further simplify patch_insn_set()/patch_insn_write() loop conditions
>  - Use min() instead of min_t() since both sides are unsigned long
>
> Samuel Holland (7):
>   riscv: jump_label: Batch icache maintenance
>   riscv: jump_label: Simplify assembly syntax
>   riscv: kprobes: Use patch_text_nosync() for insn slots
>   riscv: Simplify text patching loops
>   riscv: Pass patch_text() the length in bytes
>   riscv: Use offset_in_page() in text patching functions
>   riscv: Remove extra variable in patch_text_nosync()
>
>  arch/riscv/include/asm/jump_label.h |  4 +-
>  arch/riscv/include/asm/patch.h      |  2 +-
>  arch/riscv/kernel/jump_label.c      | 16 +++++--
>  arch/riscv/kernel/patch.c           | 69 ++++++++++++++---------------
>  arch/riscv/kernel/probes/kprobes.c  | 19 ++++----
>  arch/riscv/net/bpf_jit_comp64.c     |  7 +--
>  6 files changed, 63 insertions(+), 54 deletions(-)

I don't have any issues with this, but given that we've run into some 
possible text patching bug with this ftrace thing I'm just going to hold 
off until 6.11 for these.  Maybe that's a bit too conservative, but with 
the bug only manifesting on HW it might be tough to sort out.