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 18:23 +0100, Peter Zijlstra wrote:
> On Tue, Dec 19, 2017 at 05:01:55PM +0100, Peter Zijlstra wrote:
> > 
> > On Tue, Dec 19, 2017 at 11:42:41PM +0800, Zhang Rui wrote:
> > > 
> > > On Tue, 2017-12-19 at 16:23 +0100, Peter Zijlstra wrote:
> > > 
> > > > 
> > > > [    0.000000] ACPI: INT_SRC_OVR (bus 0 bus_irq 0 global_irq 2
> > > > dfl dfl)
> > > > [    0.000000] ACPI: IRQ0 used by override.
> > > > 
> > > > So your ACPI table has an override for IRQ2 and routes it to
> > > > IRQ0.
> > ^ this
> > 
> > > 
> > > > 
> > > >  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
> > > But AFAICS, the HPET emulated timer interrupts goes to IRQ0
> > Right, so see that ACPI override, that routes I/O APIC IRQ2 to
> > IRQ0, or
> > it _should_.
> > 
> > Clearly something is messed up here.. but I've no idea what. That
> > whole
> > IRQ routing stuff is confusing.
> Does this help?
> 
No.

thanks,
rui
> diff --git a/arch/x86/kernel/time.c b/arch/x86/kernel/time.c
> index 749d189f8cd4..45675072771c 100644
> --- a/arch/x86/kernel/time.c
> +++ b/arch/x86/kernel/time.c
> @@ -69,8 +69,6 @@ static struct irqaction irq0  = {
>  
>  static void __init setup_default_timer_irq(void)
>  {
> -	if (!nr_legacy_irqs())
> -		return;
>  	setup_irq(0, &irq0);
>  }
>