RE: [Xen-ia64-devel] RE: Latest status about multiple domains on XEN/IPF

["Magenheimer, Dan (HP Labs Fort Collins)" <dan.magenheimer@xxxxxx>]

> diff -r 55bc6698c889 xen/arch/ia64/xen/vcpu.c
> @@ -631,6 +632,16 @@
>  {
>       UINT64 *p, *q, *r, bits, bitnum, mask, i, vector;
>  
> +     /* Always check pending event, since guest may just ack the
> +      * event injection without handle. Later guest may throw out
> +      * the event itself.
> +      */
> +     if (event_pending(vcpu) && 
> +             !test_bit(vcpu->vcpu_info->arch.evtchn_vector,
> +                     &PSCBX(vcpu, insvc[0])))
> +             test_and_set_bit(vcpu->vcpu_info->arch.evtchn_vector,
> +                     &PSCBX(vcpu, irr[0]));
> +
>       p = &PSCBX(vcpu,irr[3]);
>       /* q = &PSCB(vcpu,delivery_mask[3]); */
>       r = &PSCBX(vcpu,insvc[3]);

Why is the line that sets the irr bit calling
test_and_set_bit() rather than just set_bit()?
Even better, why not call vcpu_pend_interrupt()
which also sets the pending_interruption flag?

Also, why does the irr bit get set only if insvc is
not set?  Isn't it possible to pend one interrupt
while another is in-service?

Thanks,
Dan

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