linux-kernel - RE: [PATCH v4] panic: add panic_force_cpu= parameter to redirect panic to a specific CPU

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Message-ID:
 <MRWPR09MB802271B39110228AA354FD8D8F8FA@MRWPR09MB8022.eurprd09.prod.outlook.com>
Date: Wed, 14 Jan 2026 21:57:21 +0000
From: Pnina Feder <PNINA.FEDER@...ileye.com>
To: Peter Zijlstra <peterz@...radead.org>
CC: "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"pmladek@...e.com" <pmladek@...e.com>, "bhe@...hat.com" <bhe@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"lkp@...el.com" <lkp@...el.com>, "mgorman@...e.de" <mgorman@...e.de>,
	"mingo@...hat.com" <mingo@...hat.com>, "rostedt@...dmis.org"
	<rostedt@...dmis.org>, "senozhatsky@...omium.org" <senozhatsky@...omium.org>,
	"tglx@...utronix.de" <tglx@...utronix.de>, Vladimir Kondratiev
	<Vladimir.Kondratiev@...ileye.com>
Subject: RE: [PATCH v4] panic: add panic_force_cpu= parameter to redirect
 panic to a specific CPU

Hi,

> > > Also, if this is a 'requirement' for kexec or the like, this 
> > > shouldn't be a command line argument, but something that's set-up by 
> > > kexec itself for functional reasons.
> > 
> > Since the redirection needs to happen before other CPUs are stopped, 
> > would a sysctl be preferable? The user could set it when loading the 
> > crash kernel.
> 
> I was more thinking about platform setup, it would set this on boot, and equally dis-allow hot-unplug of the magical CPU.

Thanks for the suggestion.

I was thinking of this as a fixed platform requirement that is known at boot and needs to apply from the start of the panic path. Handling it via platform setup would likely involve additional CPU hotplug and lifecycle handling, which seemed unnecessary for this case. A boot-time parameter felt like a simple and explicit way to express that constraint.

Please let me know if this sounds reasonable.

Thanks,
Pnina