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

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Date: Tue, 5 Mar 2024 07:59:37 +0000
From: Conor Dooley <conor.dooley@...rochip.com>
To: Anup Patel <apatel@...tanamicro.com>
CC: Björn Töpel <bjorn@...nel.org>, 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 05, 2024 at 08:33:30AM +0530, Anup Patel wrote:
> 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.

Whether or not this is backportable, if it fixes a bug, it should get
a Fixes: tag for the commit that it fixes. Fixes: isn't "the backport"
tag, cc: stable is.

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