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

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Date: Mon, 04 Mar 2024 21:24:09 +0100
From: Björn Töpel <bjorn@...nel.org>
To: Conor Dooley <conor@...nel.org>, Alexandre Ghiti
 <alexghiti@...osinc.com>, Anup Patel <anup@...infault.org>
Cc: 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

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?