Hi Ian, On 13/01/15 15:55, Ian Campbell wrote: > On Fri, 2014-12-12 at 14:43 +0000, Julien Grall wrote: >> This help for guest interrupts debugging. If the vIRQ is not allocate, >> this means that nothing is wired to it. > > Should we short circuit the rest of the enable operation for this IRQ > then? i.e. implement such writes as ignored, e.g. not reflect it in > reads of ISENABLER etc. > > What (if anything) does the GIC spec have to say on the subject?
"A register bit corresponding to an unimplemented interrupt is RAZ/WI." The goal of this print was mostly for debugging physical IRQ routed to a guest. I could extend to ignore write to any register that should be RAZ/WI for this specific interrupt. But, I will have to think about possible race condition with the hypercall to route a physical IRQ to the guest (see [1] and [2]). The vIRQ is reserved before the physical IRQ is effectively routed. So a guest may enable the vIRQ before this time lapse. Though, the patch [2] protected for a such case. Not sure if we should take care of a such case. Regards, -- Julien Grall _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel
