linux-kernel - Re: [PATCH -fixes] riscv: patch: Flush the icache right after patching to avoid illegal insns

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Message-ID: <20240626-astrology-fructose-275fb799ebce@spud>
Date: Wed, 26 Jun 2024 13:59:20 +0100
From: Conor Dooley <conor@...nel.org>
To: Alexandre Ghiti <alexghiti@...osinc.com>
Cc: Steven Rostedt <rostedt@...dmis.org>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Paul Walmsley <paul.walmsley@...ive.com>,
	Palmer Dabbelt <palmer@...belt.com>,
	Albert Ou <aou@...s.berkeley.edu>,
	Björn Töpel <bjorn@...osinc.com>,
	Andy Chiu <andy.chiu@...ive.com>,
	Puranjay Mohan <puranjay12@...il.com>, linux-kernel@...r.kernel.org,
	linux-trace-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org,
	Conor Dooley <conor.dooley@...rochip.com>
Subject: Re: [PATCH -fixes] riscv: patch: Flush the icache right after
 patching to avoid illegal insns

On Mon, Jun 24, 2024 at 10:21:41AM +0200, Alexandre Ghiti wrote:
> We cannot delay the icache flush after patching some functions as we may
> have patched a function that will get called before the icache flush.
> 
> The only way to completely avoid such scenario is by flushing the icache
> as soon as we patch a function. This will probably be costly as we don't
> batch the icache maintenance anymore.
> 
> Fixes: 6ca445d8af0e ("riscv: Fix early ftrace nop patching")
> Reported-by: Conor Dooley <conor.dooley@...rochip.com>
> Closes: https://lore.kernel.org/linux-riscv/20240613-lubricant-breath-061192a9489a@wendy/
> Signed-off-by: Alexandre Ghiti <alexghiti@...osinc.com>

So, I can't even test this right now :/ The issue is annoying enough to
reproduce that same config + compiler + commit isn't enough.

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