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

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Message-ID: <20260108113637.04c830e6@gandalf.local.home>
Date: Thu, 8 Jan 2026 11:36:37 -0500
From: Steven Rostedt <rostedt@...dmis.org>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Pnina Feder <pnina.feder@...ileye.com>, akpm@...ux-foundation.org,
 pmladek@...e.com, bhe@...hat.com, linux-kernel@...r.kernel.org,
 lkp@...el.com, mgorman@...e.de, mingo@...hat.com, senozhatsky@...omium.org,
 tglx@...utronix.de, vkondra@...ileye.com
Subject: Re: [PATCH v4] panic: add panic_force_cpu= parameter to redirect
 panic to a specific CPU

On Thu, 8 Jan 2026 08:48:57 +0100
Peter Zijlstra <peterz@...radead.org> wrote:

> > +	panic_force_cpu=
> > +			[KNL,SMP] Force panic handling to execute on a specific CPU.
> > +			Format: <cpu number>
> > +			Some platforms require panic handling to occur on a
> > +			specific CPU for the crash kernel to function correctly.
> > +			This can be due to firmware limitations, interrupt routing
> > +			constraints, or platform-specific requirements where only
> > +			a particular CPU can safely enter the crash kernel.
> > +			When set, panic() will redirect execution to the specified
> > +			CPU before proceeding with the normal panic and kexec flow.
> > +			If the target CPU is offline or unavailable, panic proceeds
> > +			on the current CPU.  
> 
> It this stays; it should have a warning that it makes the panic less reliable.

Agreed. It should probably end with:

              This option should only be used for systems with the above
              constraints as it will cause the panic operation to be less
              reliable.

-- Steve