Re: [Xen-devel] Windows SMP

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

On 29/12/2008 09:40, "James Harper" <james.harper@xxxxxxxxxxxxxxxx> wrote:

> Assuming the hypervisor route, if I understand correctly it could go
> like this:

Either of your described approaches could work. This doesn't involve qemu at
all, since APIC emulation is done within Xen. So it'll be a new hvm_op
hypercall either way. Getting Xen to do the patching isn't a bad idea. Might
also be worth looking at how KVM does it to get some further ideas.

I don't think your patched routine has to be any more complex than filtering
out TPR writes which don't change the TPR value. Again you could check KVM
for this. And of course the TPR write in your patch routine should be
skipped by the trap-and-patch mechanism. :-)

>> Both. As well as the VMEXIT you have a run through the instruction
>> emulator
>> and into the apic device model. It sucks pretty bad if you do it
> often.
> 
> I see. It's the sum of a whole load of tiny overheads that adds up...

Two fairly big overheads.

 -- Keir



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