x86, ioapic: Restore the mask bit correctly in eoi_ioapic_irq()

x86, ioapic: Restore the mask bit correctly in eoi_ioapic_irq()

For older IO-APIC's, we were clearing the remote-IRR by changing
the RTE trigger mode to edge and then back to level. We wanted
to mask the RTE during this process, so we were essentially
doing mask+edge and then to unmask+level.

As part of the commit ca64c47cecd0321b2e0dcbd7aaff44b68ce20654,
we moved this EOI process earlier where the IO-APIC RTE is
masked. So we were wrongly unmasking it in the eoi_ioapic_irq().

So change the remote-IRR clear sequence in eoi_ioapic_irq() to
mask + edge and then restore the previous RTE entry which will
restore the mask status as well as the level trigger.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Maciej W. Rozycki <macro@linux-mips.org>
Cc: Thomas Renninger <trenn@suse.de>
Cc: Rafael Wysocki <rjw@novell.com>
Cc: lchiquitto@novell.com
Cc: jbeulich@novell.com
Cc: yinghai@kernel.org
Link: http://lkml.kernel.org/r/20110825190657.210286410@sbsiddha-desk.sc.intel.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>