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From:   Thomas Gleixner <tglx@linutronix.de>
To:     Borislav Petkov <bp@suse.de>, James Feeney <james@nurealm.net>
Cc:     linux-smp@vger.kernel.org, Jens Axboe <axboe@kernel.dk>,
        lkml <linux-kernel@vger.kernel.org>,
        Zhang Rui <rui.zhang@intel.com>,
        Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
        x86-ml <x86@kernel.org>
Subject: Re: [PATCH] x86/thermal: Fix LVT thermal setup for SMI delivery mode
In-Reply-To: <YK905sC/2cVOYo6I@zn.tnic>
References: <YKWAt1zLM2vfv4Sp@zn.tnic> <e7701de5-35f3-da9d-7339-df2de6d8b3cf@nurealm.net> <YKYqABhSTTUG8cgV@zn.tnic> <a264eaef-1c94-77e1-dfbf-e436a41588be@nurealm.net> <YKjJfu4kRDflQS5e@zn.tnic> <373464e3-b8a0-0fe0-b890-41df0eecf090@nurealm.net> <YKqLSqIM7Gi5x+IA@zn.tnic> <b550a241-2097-cf4b-cc41-e4d0a45cda72@nurealm.net> <YKtbBXZGpVZS1M4R@zn.tnic> <1f6c70f4-6680-d6ea-465a-548dc7698317@nurealm.net> <YK905sC/2cVOYo6I@zn.tnic>
Date:   Thu, 27 May 2021 13:49:42 +0200
Message-ID: <87h7io8kh5.ffs@nanos.tec.linutronix.de>
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On Thu, May 27 2021 at 12:31, Borislav Petkov wrote:
> @@ -1226,6 +1227,14 @@ void __init setup_arch(char **cmdline_p)
>  
>  	x86_init.timers.wallclock_init();
>  
> +	/*
> +	 * This needs to run before setup_local_APIC() which soft-disables the
> +	 * local APIC temporarily and that masks the thermal LVT interrupt,
> +	 * leading to softlockups on machines which have configured SMI
> +	 * interrupt delivery.
> +	 */
> +	therm_lvt_init();

That works, but TBH, it's a hack....

What I really fail to understand is how disabling that LVT entry makes
the machine lock up. 

Also if disabling this entry is causing the BIOS/SMM gunk to go south, then
disabling CONFIG_X86_THERMAL_VECTOR should have the same effect.

Which made me look at other places like lapic_suspend/resume which does
the save/restore Kconfig conditional as well.

Thanks,

        tglx