linux-kernel - Re: [patch v3 7/7] x86/smp: Put CPUs into INIT on shutdown if possible

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Date:   Tue, 20 Jun 2023 12:27:43 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        Mario Limonciello <mario.limonciello@....com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Tony Battersby <tonyb@...ernetics.com>,
        Ashok Raj <ashok.raj@...ux.intel.com>,
        Tony Luck <tony.luck@...el.com>,
        Arjan van de Veen <arjan@...ux.intel.com>,
        Eric Biederman <ebiederm@...ssion.com>,
        Ashok Raj <ashok.raj@...el.com>
Subject: Re: [patch v3 7/7] x86/smp: Put CPUs into INIT on shutdown if
 possible

On Thu, Jun 15, 2023 at 10:34:00PM +0200, Thomas Gleixner wrote:
> @@ -202,7 +206,27 @@ static void native_stop_other_cpus(int w
>  			udelay(1);
>  	}
>  
> -	/* if the REBOOT_VECTOR didn't work, try with the NMI */
> +	/*
> +	 * Park all other CPUs in INIT including "offline" CPUs, if
> +	 * possible. That's a safe place where they can't resume execution
> +	 * of HLT and then execute the HLT loop from overwritten text or
> +	 * page tables.
> +	 *
> +	 * The only downside is a broadcast MCE, but up to the point where
> +	 * the kexec() kernel brought all APs online again an MCE will just
> +	 * make HLT resume and handle the MCE. The machine crashs and burns

"crashes"

With that

Reviewed-by: Borislav Petkov (AMD) <bp@...en8.de>

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette