linux-kernel - Re: Regression: unable to boot after commit bd9240a18edf ("x86/apic: Add TSC_DEADLINE quirk due to errata")

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Date:   Tue, 19 Dec 2017 16:31:33 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Zhang Rui <rui.zhang@...el.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>, linux-x86 <x86@...nel.org>,
        Len Brown <len.brown@...el.com>,
        "Chen, Yu C" <yu.c.chen@...el.com>
Subject: Re: Regression: unable to boot after commit bd9240a18edf ("x86/apic:
 Add TSC_DEADLINE quirk due to errata") - Surface Pro 4 SKL

On Tue, Dec 19, 2017 at 04:23:07PM +0100, Peter Zijlstra wrote:
> On Tue, Dec 19, 2017 at 06:48:24PM +0800, Zhang Rui wrote:
> > On Mon, 2017-12-18 at 21:28 +0100, Peter Zijlstra wrote:
> > > Hi, can you see if this makes you Surface boot?
> > > 
> > No, it does not boot.
> 
> So I'm confused on the lapic calibration.
> 
> That stuff uses global_clock_event, which is initially the i8253 (PIT),
> but because !PIC this thing won't be there either on your platform.
> 
> Then we initialize I/O APIC, and your machine has:
> 
> [    0.000000] IOAPIC[0]: apic_id 2, version 32, address 0xfec00000, GSI 0-119
> [    0.000000] ACPI: INT_SRC_OVR (bus 0 bus_irq 0 global_irq 2 dfl dfl)
> [    0.000000] ACPI: INT_SRC_OVR (bus 0 bus_irq 9 global_irq 9 high level)
> [    0.000000] ACPI: IRQ0 used by override.
> [    0.000000] ACPI: IRQ9 used by override.
> 
> So your ACPI table has an override for IRQ2 and routes it to IRQ0.
> 
> Then we initialize HPET, and we _always_ do hpet_enable_legacy_int(),
> which sets the LegacyRouting bit. The HPET document says:
> 
>   If the ENABLE_CNF bit and the LEG_RT_CNF bit are both set, then the
>   interrupts will be routed as follows:
> 
>     Timer 0 will be routed to IRQ0 in Non-APIC or IRQ2 in the I/O APIC
>     Timer 1 will be routed to IRQ8 in Non-APIC or IRQ8 in the I/O APIC
>     Timer 2-n will be routed as per the routing in the timer n config registers.
> 
>   If the LegacyReplacement Route bit is set, the individual routing bits
>   for timers 0 and 1 (APIC or FSB) will have no impact.
> 
> And then we set global_clock_event to &hpet_clockevent.
> 
> At this point that _SHOULD_ work afaict, even without actual PIC
> present.
> 
> Sometime after that we call into calibrate_APIC_clock() -- because
> !TSC_DEADLINE -- and this is where you get stuck, because
> global_clock_event is not in fact delivering interrupts.
> 
> Thomas may have more clue, we'll have to wait for him to have a
> time-slot available.

What does your /proc/interrupts look like (on a tsc-deadline boot) ?

0: is the HPET, LOC: is the lapic/tsc-deadline

On my SKL desktop I get 21 PIT/HPET ticks on CPU0 before lapic takes over.