Re: Regression: unable to boot after commit bd9240a18edf ("x86/apic: Add TSC_DEADLINE quirk due to errata") - Surface Pro 4 SKL

[Peter Zijlstra <peterz@infradead.org>]

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.