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

Avi Kivity
2007-04-10T16:11:36Z

Gregory Haskins wrote:
>>>> On Tue, Apr 10, 2007 at 11:39 AM, in message <461B7755.BA47.005A.0-Et1tbQHTxzrQT0dZR+AlfA@public.gmane.org>,
>>>>
> Gregory Haskins wrote:
>
>> We could change the API to handle the pending condition as a tri-level
>>
>
> I just thought of a better way. Leave the return value as a boolean, but use the concept of the mask_reasons. It simplifies the logic, and allows the irqdevice to register for additional VMEXITs regardless of whether its currently injecting something or not. So we have:
>
> spin_lock(vcpu- >irq_lock)
> vcpu->exit_reasons = 0;
> nmi = !irq_window_open(vcpu)
> if (vcpu- >irq- >pending(nmi, &mask_reasons))
> inject(vcpu, vcpu- >irq- >read_vector(nmi))
> if (mask_reasons) {
> if (mask_reasons & MASKREASON_TPR)
> vcpu->exit_reasons &= TPR;
> /* etc */
> }
> spin_unlock(vcpu- >irq_lock)
>

It's more complex than that; you need to program the hardware to exit on
a specific threshold level of tpr values (e.g. exit when tpr <= n).

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.

--
error compiling committee.c: too many arguments to function