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SubjectRe: setup_boot_APIC_clock() NULL dereference during early boot on reduced hardware platforms
On Thu, Aug 1, 2019 at 3:35 PM Thomas Gleixner <tglx@linutronix.de> wrote:
>
> On Thu, 1 Aug 2019, Aubrey Li wrote:
> > On Thu, Aug 1, 2019 at 2:26 PM Daniel Drake <drake@endlessm.com> wrote:
> > > global_clock_event is NULL here. This is a "reduced hardware" ACPI
> > > platform so acpi_generic_reduced_hw_init() has set timer_init to NULL,
> > > avoiding the usual codepaths that would set up global_clock_event.
> > >
> > IIRC, acpi_generic_reduced_hw_init() avoids initializing PIT, the status of
> > this legacy device is unknown in ACPI hw-reduced mode.
> >
> > > I tried the obvious:
> > > if (!global_clock_event)
> > > return -1;
> > >
> > No, the platform needs a global clock event, can you turn on some other
>
> Wrong. The kernel boots perfectly fine without a global clock event. But
> for that the TSC and LAPIC frequency must be known.

I think LAPIC fast calibrate is only supported on intel platform, while
Daniel's box is an AMD platform. That's why lapic_init_clockevent() failed
and fall into the code path which needs a global clock event.

Thanks,
-Aubrey

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