Well, it is the very intent of the DMI quirk to set apic1 and pin1 both
to -1, as a result of IRQ0 being absent from our I/O APIC interrupt
routing table. Therefore if the quirk did indeed work, a call to
clear_IO_APIC_pin() is useless and likely harmful as its callees don't do
range checking (my understanding of code is it results in random poking at
the local APIC through the FIX_APIC_BASE fixmap). There should be nothing
to clear too, as interrupt redirection entries for all the I/O APIC inputs
are cleared (the mask is set to 1 and the remaining fields zeroed) when
clear_IO_APIC() is called from enable_IO_APIC() upon initialization and
all the unused ones (not referred to from anywhere in the interrupt
routing table) are never touched afterwards.
Maciej
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