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

Avi Kivity
2009-05-25T04:56:39Z

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.