linux-kernel - Re: [PATCH] riscv: Fix text patching when icache flushes use IPIs

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Message-ID: <87v87091e5.fsf@all.your.base.are.belong.to.us>
Date: Wed, 07 Feb 2024 08:30:58 +0100
From: Björn Töpel <bjorn@...nel.org>
To: Alexandre Ghiti <alexghiti@...osinc.com>, Paul Walmsley
 <paul.walmsley@...ive.com>, Palmer Dabbelt <palmer@...belt.com>, Albert Ou
 <aou@...s.berkeley.edu>, Anup Patel <anup@...infault.org>, 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
Cc: Alexandre Ghiti <alexghiti@...osinc.com>, Björn Töpel <bjorn@...osinc.com>
Subject: Re: [PATCH] riscv: Fix text patching when icache flushes use IPIs

Alexandre Ghiti <alexghiti@...osinc.com> writes:

> For now, we use stop_machine() to patch the text and when we use IPIs for
> remote icache flushes, the system hangs since the irqs are disabled on all
> cpus.
>
> So instead, make sure every cpu executes the stop_machine() patching
> function which emits a local icache flush and then avoids the use of
> IPIs.
>
> Co-developed-by: Björn Töpel <bjorn@...osinc.com>
> Signed-off-by: Björn Töpel <bjorn@...osinc.com>
> Signed-off-by: Alexandre Ghiti <alexghiti@...osinc.com>

FWIW, the BPF selftests pass nicely with this (especially the
fentry/fexit tests ;-)). I don't know if it's worth much saying that
your own stuff was tested, but here goes:

Tested-by: Björn Töpel <bjorn@...osinc.com>