On Fri, Dec 07, 2012 at 01:00:18AM +0000, Zhang, Yang Z wrote: > Marcelo Tosatti wrote on 2012-12-07: > >>> How about to recaculate irr_pending according the VIRR on each vmexit? > >>> > >> No need really. Since HW can only clear VIRR the only situation that may > >> happen is that irr_pending will be true but VIRR is empty and > >> apic_find_highest_irr() will return correct result in this case. > >> > >> If we will see a lot of unneeded irr scans because of stale irr_pending > >> value we can do irr_pending = rvi != 0 on vmexit. > >> > >> -- > >> Gleb. > > > > Yes, it is harmless ATM. But its clearer if irr_pending is not used when > > virtual interrupt delivery is in effect (that is, just skip irr_pending > > if virtual interrupt delivery is enabled). > irr_pending still is useful in virtual interrupt delivery case. Or else, as gleb said ,there may be lots of unneeded irr scan. > Actually, looking at it close, irr_pending will always be true (and thus effectively disabled without any additional checks) since it is cleared only in kvm_get_apic_interrupt() which will not be called with vid enabled. It is racy to do irr_pending = rvi != 0 on vmexit either. The code should be something like that: irr_pending = (rvi != 0) ? : apic_search_irr(apic) != -1; But we do not want to do that on each exit since rvi will be mostly zero and irr is, more often than not, empty. -- Gleb. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
