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From: Anup Patel <apatel@ventanamicro.com>
Date: Tue, 5 Mar 2024 08:33:30 +0530
Message-ID: <CAK9=C2Xjgr9_H-sHkmAAc95dAm2jd+_dxLUxSM3RM3NrQJFKGQ@mail.gmail.com>
Subject: Re: [PATCH v3 2/2] riscv: Fix text patching when IPI are used
To: =?UTF-8?B?QmrDtnJuIFTDtnBlbA==?= <bjorn@kernel.org>
Cc: Conor Dooley <conor@kernel.org>, Alexandre Ghiti <alexghiti@rivosinc.com>, 
	Anup Patel <anup@brainfault.org>, Paul Walmsley <paul.walmsley@sifive.com>, 
	Palmer Dabbelt <palmer@dabbelt.com>, Albert Ou <aou@eecs.berkeley.edu>, 
	Andrea Parri <andrea@rivosinc.com>, Samuel Holland <samuel.holland@sifive.com>, 
	Steven Rostedt <rostedt@goodmis.org>, Masami Hiramatsu <mhiramat@kernel.org>, 
	Mark Rutland <mark.rutland@arm.com>, linux-riscv@lists.infradead.org, 
	linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, 
	=?UTF-8?B?QmrDtnJuIFTDtnBlbA==?= <bjorn@rivosinc.com>, 
	Andrea Parri <parri.andrea@gmail.com>
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On Tue, Mar 5, 2024 at 1:54=E2=80=AFAM Bj=C3=B6rn T=C3=B6pel <bjorn@kernel.=
org> wrote:
>
> Conor Dooley <conor@kernel.org> writes:
>
> > On Thu, Feb 29, 2024 at 01:10:56PM +0100, Alexandre Ghiti wrote:
> >> For now, we use stop_machine() to patch the text and when we use IPIs =
for
> >> remote icache flushes (which is emitted in patch_text_nosync()), the s=
ystem
> >> hangs.
> >>
> >> So instead, make sure every CPU executes the stop_machine() patching
> >> function and emit a local icache flush there.
> >>
> >> Co-developed-by: Bj=C3=B6rn T=C3=B6pel <bjorn@rivosinc.com>
> >> Signed-off-by: Bj=C3=B6rn T=C3=B6pel <bjorn@rivosinc.com>
> >> Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
> >> Reviewed-by: Andrea Parri <parri.andrea@gmail.com>
> >
> > What commit does this fix?
>
> Hmm. The bug is exposed when the AIA IPI are introduced, and used
> (instead of the firmware-based).
>
> I'm not sure this is something we'd like backported, but rather a
> prerequisite to AIA.
>
> @Anup @Alex WDYT?
>

The current text patching never considered IPIs being injected
directly in S-mode from hart to another so we are seeing this
issue now with AIA IPIs.

We certainly don't need to backport this fix since it's more
of a preparatory fix for AIA IPIs.

Regards,
Anup