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

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Message-ID:
 <MRWPR09MB8022ACA10533A9A011C447CA8F85A@MRWPR09MB8022.eurprd09.prod.outlook.com>
Date: Thu, 8 Jan 2026 20:14:02 +0000
From: Pnina Feder <PNINA.FEDER@...ileye.com>
To: Steven Rostedt <rostedt@...dmis.org>, 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>, "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 Steve,

> 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

I have added your suggestion to the documentation on v5.

Thanks,
Pnina