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From: =?utf-8?B?QmrDtnJuIFTDtnBlbA==?= <bjorn@kernel.org>
To: Conor Dooley <conor.dooley@microchip.com>, Anup Patel
 <apatel@ventanamicro.com>
Cc: Conor Dooley <conor@kernel.org>, Alexandre Ghiti
 <alexghiti@rivosinc.com>, Anup Patel <anup@brainfault.org>, Paul Walmsley
 <paul.walmsley@sifive.com>, Palmer
 Dabbelt <palmer@dabbelt.com>, Albert Ou <aou@eecs.berkeley.edu>, Andrea
 Parri <andrea@rivosinc.com>, Samuel Holland <samuel.holland@sifive.com>,
 Steven
 Rostedt <rostedt@goodmis.org>, Masami Hiramatsu <mhiramat@kernel.org>, Mark
 Rutland <mark.rutland@arm.com>, linux-riscv@lists.infradead.org,
 linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org,
 =?utf-8?B?QmrDtnJuIFTDtnBlbA==?= <bjorn@rivosinc.com>, Andrea Parri
 <parri.andrea@gmail.com>
Subject: Re: [PATCH v3 2/2] riscv: Fix text patching when IPI are used
In-Reply-To: <20240305-sarcasm-ending-0f7946490aea@wendy>
References: <20240229121056.203419-1-alexghiti@rivosinc.com>
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 <87msrdzqxi.fsf@all.your.base.are.belong.to.us>
 <CAK9=C2Xjgr9_H-sHkmAAc95dAm2jd+_dxLUxSM3RM3NrQJFKGQ@mail.gmail.com>
 <20240305-sarcasm-ending-0f7946490aea@wendy>
Date: Tue, 05 Mar 2024 09:21:07 +0100
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Conor Dooley <conor.dooley@microchip.com> writes:

> On Tue, Mar 05, 2024 at 08:33:30AM +0530, Anup Patel wrote:
>> On Tue, Mar 5, 2024 at 1:54=E2=80=AFAM Bj=C3=B6rn T=C3=B6pel <bjorn@kern=
el.org> wrote:
>> >
>> > Conor Dooley <conor@kernel.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 IP=
Is for
>> > >> remote icache flushes (which is emitted in patch_text_nosync()), th=
e system
>> > >> hangs.
>> > >>
>> > >> So instead, make sure every CPU executes the stop_machine() patching
>> > >> function and emit a local icache flush there.
>> > >>
>> > >> Co-developed-by: Bj=C3=B6rn T=C3=B6pel <bjorn@rivosinc.com>
>> > >> Signed-off-by: Bj=C3=B6rn T=C3=B6pel <bjorn@rivosinc.com>
>> > >> Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
>> > >> Reviewed-by: Andrea Parri <parri.andrea@gmail.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?
>> >
>>=20
>> 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.
>>=20
>> 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.

I guess the question is if this *is* a fix, or rather a change required
for AIA (not a fix).