Re: Fwd: Re: [PATCH] Add irqdevice interface + userint implementation

Gregory Haskins
2007-04-10T17:58:01Z

>>> On Tue, Apr 10, 2007 at 12:11 PM, in message <461BB738.7040206-atKUWr5tajBWk0Htik3J/w@public.gmane.org>,
Avi Kivity <avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org> wrote:
>
>
> It's more complex than that;

Isn't it always ;)

> you need to program the hardware to exit on
> a specific threshold level of tpr values (e.g. exit when tpr <= n).
>

Agreed, but don't forget the TPR/CR8 will always be an exposed interface of the LAPIC and therefore readily available for factoring into the algorithm. I just am not there yet.

> It's a little sad to encode a complex condition (wait for nmi window
> opening/wait for irq window opening/wait for irq window opening with tpr
> <= n) in irqdevice, then decode it in the vcpu and program the hardware
> accordingly.

Agreed, but keep in mind that whatever we make the irqdevice do, it will have to do it in both the QEMU and in-kernel models if we want true dynamic ABI support for old userspace. I was trying to reduce the duplication of code in each model, but perhaps it's no more complex either way...TBD.

Regards,
-Greg