Xen devel - Sep 2009 - [PATCH] vt-d: enhance the support of Interrupt Remapping EIM and x2APIC

Hi Keir,
Attached are 3 patches to enhance the support of Interrupt Remapping EIM and
x2APIC in Xen.

Now Xen enables x2APIC if it finds BSP supports x2APIC, but this is not proper:
we also have to check all the VT-d engines' IR and if all IR units support
EIM, we will enable x2APIC and EIM.
EIM enables external devices to deliver interrupts (via IOAPIC or MSI) to CPUs
with >8-bit APIC ID. Without EIM, even we enabled x2APIC in CPU's side,
external devices can't deliver interrupt to CPUs with >8-bit APIC ID --
this kind of software usage is not architecturally proper. The recommended usage
model is: we should only enable x2APIC and EIM when they are both supported by
CPU and VT-d IR engines on the system.

Thanks,
-- Dexuan



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