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

[Zhang Rui <rui.zhang@intel.com>]

On Tue, 2017-12-19 at 16:31 +0100, Peter Zijlstra wrote:
> 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.
No irq0.
 LOC:     220071     210079     184892     176494   Local timer
interrupts

thanks,
rui