Re: 584c5c422f6c ("x86/ioapic: Support hot-removal of IOAPICs present during boot")

[Rui Wang]

On Sat, Sep 10, 2016 10:31 PM, Borislav Petkov wrote:
> 
> On Sat, Sep 10, 2016 at 09:11:30PM +0800, Rui Wang wrote:
> > Thanks for the analysis. Looks like acpi_gbl_root_node == 0. It is
> 
> Is ACPI_HANDLE(root_bus->bridge) == ACPI_ROOT_OBJECT?
> 
> Because this is what the code does but I can't see it from the code that the
> handle is of type ACPI_ROOT_OBJECT...
> 

I seem to have the clue. It is because ACPI_HANDLE(root_bus->bridge) == NULL.
Then this root bridge doesn't have a corresponding ACPI device. In this case
we shouldn't call acpi_ioapic_add(). This can be true for some old platforms.

If that's the case then the patch below can fix it.

Thanks
Rui