linux-kernel - Re: reserve_mem command line option causing a reboot but not by the kernel

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Message-ID: <20241008132259.52a5f274@gandalf.local.home>
Date: Tue, 8 Oct 2024 13:22:59 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: LKML <linux-kernel@...r.kernel.org>
Cc: Mike Rapoport <mike.rapoport@...il.com>, Masami Hiramatsu
 <mhiramat@...nel.org>, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 Linus Torvalds <torvalds@...ux-foundation.org>, Peter Zijlstra
 <peterz@...radead.org>, Thomas Gleixner <tglx@...utronix.de>, Ard
 Biesheuvel <ardb@...nel.org>
Subject: Re: reserve_mem command line option causing a reboot but not by the
 kernel

On Sun, 6 Oct 2024 13:32:33 -0400
Steven Rostedt <rostedt@...dmis.org> wrote:

> I don't have time to debug further. Maybe I need to look at the legacy
> grub code. I just found this interesting and decided to share. Perhaps
> someone else might hit this too?

I found that one of my old test machines also uses legacy grub, and it too
has the same issue.

It appears that grub does indeed search for "mem=" (without looking for
something before it) in the kernel command line.

  https://github.com/jezze/grub-legacy/blob/master/stage2/boot.c#L275

Thus, "reserve_mem=" (or any other "mem=" option) cannot be used with legacy
grub installs :-p

-- Steve