Re: [GIT PULL] Xen APIC hooks (with io_apic_ops)

From: Avi Kivity
Date: Mon May 25 2009 - 00:56:43 EST

Ingo Molnar wrote:
We do something similar for Windows (by patching it) very successfully; Windows likes to touch the APIC TPR ~ 100,000 times per second, usually without triggering an interrupt. We hijack these writes, do the checks in guest context, and only exit if the TPR write would trigger an interrupt.

I suspect you aware of that this is about the io-apic not the local APIC. The local apic methods are already driver-ized - and they sit closer to the CPU so they matter more to performance.

Yeah, I gave this as an example. It's very different -- io-apic vs. local apic, paravirtualization vs. patching the guest behind its back, Linux vs. Windows.

Of course if we hook the io-apic EOI we'll want to hook the local apic EOI as well.

I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.

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