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Date:   Fri, 30 Jun 2023 07:33:55 +0100
From:   Conor Dooley <conor.dooley@microchip.com>
To:     Song Shuai <suagrfillet@gmail.com>
CC:     <paul.walmsley@sifive.com>, <palmer@dabbelt.com>,
        <aou@eecs.berkeley.edu>, <ajones@ventanamicro.com>,
        <sunilvl@ventanamicro.com>, <heiko.stuebner@vrull.eu>,
        <apatel@ventanamicro.com>, <evan@rivosinc.com>,
        <greentime.hu@sifive.com>, <leyfoon.tan@starfivetech.com>,
        <linux-riscv@lists.infradead.org>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] riscv: BUG_ON() for no cpu nodes in setup_smp
Message-ID: <20230630-tightrope-clatter-6eed9875a76f@wendy>
References: <20230629105839.1160895-1-suagrfillet@gmail.com>
 <20230629-maverick-kelp-17327f04482a@wendy>
 <0787532c-4520-6d01-c50c-63df207f570c@gmail.com>
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Hey,

On Fri, Jun 30, 2023 at 11:02:18AM +0800, Song Shuai wrote:
> =E5=9C=A8 2023/6/29 20:33, Conor Dooley =E5=86=99=E9=81=93:
> > On Thu, Jun 29, 2023 at 06:58:39PM +0800, Song Shuai wrote:
> > > When booting with ACPI tables, the tiny devictree created by
> > > EFI Stub doesn't provide cpu nodes.
> >=20
>=20
> "When only the ACPI tables are passed to kernel, the tiny..."
> That seems more accurate. We can use "acpi=3D" kernel
> parameter to manually enable/disable ACPI.
>=20
> > What are the conditions that are required to reproduce this issue?
> > When booting with ACPI, why is acpi_disabled true?
> > In my naivety, that seems like a bigger problem to address. >
>=20
> Actually, I appended the "acpi=3Doff" to kernel cmdline for testing the "=
off"
> option. That would set acpi_disabled as true.

Yeah, I figured it was intentionally misconfiguration of your kernel,
given that you've tested other niche conditions and reported bugs, just
was not clear from your commit message whether this was a real bugTM
that should be fixed, or some sort of "you booted a kernel that can't be
used on this system".

> > > That's unclear, so bug for no cpu nodes before
> > > of_parse_and_init_cpus().
> >=20
> > What is unclear? That the reason for the BUG() was that there were no
> > cpu nodes, since it could also be that there were CPU nodes but they
> > were disabled etc?
>=20
> The BUG() in of_parse_and_init_cpus() indicates there was no boot cpu fou=
nd
> in the devicetree , not there were no cpu nodes in the devices.
> That's the "unclear" I mean.

Yup, please put that in the commit message so that people don't have to
figure out your intent ;)

> > Or, better yet, move the whole thing into of_parse_and_init_cpus() in
> > the first place? You could drop most of the comment in the process,
> > since I think the details of how you hit this problem would likely not
> > be helpful to anyone that hit it under different conditions.

> ok, I'll apply these comments if you're ok with my replies.

Yup, thanks!

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