linux-kernel - Re: setup_boot_APIC_clock() NULL dereference during early boot on reduced hardware platforms

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Date:   Thu, 8 Aug 2019 22:36:47 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     "Lendacky, Thomas" <Thomas.Lendacky@....com>
cc:     "Li, Aubrey" <aubrey.li@...ux.intel.com>,
        Aubrey Li <aubrey.intel@...il.com>,
        Daniel Drake <drake@...lessm.com>,
        "x86@...nel.org" <x86@...nel.org>, Ingo Molnar <mingo@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>,
        Linux Kernel <linux-kernel@...r.kernel.org>,
        Endless Linux Upstreaming Team <linux@...lessm.com>
Subject: Re: setup_boot_APIC_clock() NULL dereference during early boot on
 reduced hardware platforms

Tom,

On Thu, 1 Aug 2019, Lendacky, Thomas wrote:
> On 8/1/19 5:13 AM, Thomas Gleixner wrote:
> >   2.1.9 Timers
> > 
> >    Each core includes the following timers. These timers do not vary in
> >    frequency regardless of the current P-state or C-state.
> > 
> >    * Core::X86::Msr::TSC; the TSC increments at the rate specified by the
> >      P0 Pstate. See Core::X86::Msr::PStateDef.
> > 
> >    * The APIC timer (Core::X86::Apic::TimerInitialCount and
> >      Core::X86::Apic::TimerCurrentCount), which increments at the rate of
> >      2xCLKIN; the APIC timer may increment in units of between 1 and 8.
> > 
> > The Ryzens use a 100MHz input clock for the APIC normally, but I'm not sure
> > whether this is subject to overclocking. If so then it should be possible
> > to figure that out somehow. Tom?
> 
> Let me check with the hardware folks and I'll get back to you.

any update on this? The problem seems to come in from several sides now.

Thanks,

	tglx