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Date: Tue, 28 Nov 2017 10:34:27 +0100 (CET)
From: Thomas Gleixner <tglx@linutronix.de>
To: Zhang Rui <rui.zhang@intel.com>
cc: Peter Zijlstra <peterz@infradead.org>,
        LKML <linux-kernel@vger.kernel.org>, linux-x86 <x86@kernel.org>,
        Len Brown <len.brown@intel.com>, "Chen, Yu C" <yu.c.chen@intel.com>
Subject: Re: Regression: unable to boot after commit bd9240a18edf ("x86/apic:
 Add TSC_DEADLINE quirk due to errata") - Surface Pro 4 SKL
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On Tue, 28 Nov 2017, Zhang Rui wrote:

> On Tue, 2017-11-28 at 09:14 +0100, Peter Zijlstra wrote:
> > On Tue, Nov 28, 2017 at 10:08:53AM +0800, Zhang Rui wrote:
> > > 
> > > Hi, All,
> > > 
> > > My Surface Pro 4 is unable to boot after 4.12. The symptom is that
> > > kernel freezes during boot, and the last message in the screen is
> > > loading the initrd image. And I have bisected it to this commit
> > > 
> > > +//	DEADLINE_MODEL_MATCH_REV ( INTEL_FAM6_SKYLAKE_MOBILE,	
> > > 0xb2),
> > And what microcode version do you run? Have you installed the latest
> > microcode package and updated your initrd to include it? My skylake
> > is
> > running 0xba.
> 
> No, I didn't upgrade my microcode.
> 
> $ cat /proc/cpuinfo
> ...
> processor	: 0
> vendor_id	: GenuineIntel
> cpu family	: 6
> model		: 78
> model name	: Intel(R) Core(TM) i7-6650U CPU @ 2.20GHz
> stepping	: 3
> microcode	: 0x9e
> ...
> 
> I suppose the problem should be gone if I upgrade the microcode.
> But the real problem to me is that the system FREEZES after kernel
> upgrade.

Confused. So the match disables the deadline timer due to 0x9e < 0xb2. And
not having deadline timer makes the boot fail despite the fact that
deadline timer is borked with microcode < 0xb2.

Can you verify by adding 'lapic=notscdeadline' to the command line of a
'working' kernel? That should cause a freeze as well then.

Thanks,

	tglx