linux-kernel - Re: [PATCH v3 2/2] riscv: Fix text patching when IPI are used

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Date: Tue, 5 Mar 2024 08:33:30 +0530
From: Anup Patel <apatel@...tanamicro.com>
To: Björn Töpel <bjorn@...nel.org>
Cc: Conor Dooley <conor@...nel.org>, Alexandre Ghiti <alexghiti@...osinc.com>, 
	Anup Patel <anup@...infault.org>, Paul Walmsley <paul.walmsley@...ive.com>, 
	Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>, 
	Andrea Parri <andrea@...osinc.com>, Samuel Holland <samuel.holland@...ive.com>, 
	Steven Rostedt <rostedt@...dmis.org>, Masami Hiramatsu <mhiramat@...nel.org>, 
	Mark Rutland <mark.rutland@....com>, linux-riscv@...ts.infradead.org, 
	linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org, 
	Björn Töpel <bjorn@...osinc.com>, 
	Andrea Parri <parri.andrea@...il.com>
Subject: Re: [PATCH v3 2/2] riscv: Fix text patching when IPI are used

On Tue, Mar 5, 2024 at 1:54 AM Björn Töpel <bjorn@...nel.org> wrote:
>
> Conor Dooley <conor@...nel.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 system
> >> hangs.
> >>
> >> So instead, make sure every CPU executes the stop_machine() patching
> >> function and emit a local icache flush there.
> >>
> >> Co-developed-by: Björn Töpel <bjorn@...osinc.com>
> >> Signed-off-by: Björn Töpel <bjorn@...osinc.com>
> >> Signed-off-by: Alexandre Ghiti <alexghiti@...osinc.com>
> >> Reviewed-by: Andrea Parri <parri.andrea@...il.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