On Wed, May 16, 2012 at 08:58:57PM +0300, Michael S. Tsirkin wrote: > On Wed, May 16, 2012 at 02:20:58PM -0300, Marcelo Tosatti wrote: > > On Wed, May 16, 2012 at 07:22:47PM +0300, Michael S. Tsirkin wrote: > > > On Wed, May 16, 2012 at 12:49:40PM -0300, Marcelo Tosatti wrote: > > > > > @@ -1245,9 +1306,20 @@ int kvm_get_apic_interrupt(struct kvm_vcpu *vcpu) > > > > > int vector = kvm_apic_has_interrupt(vcpu); > > > > > struct kvm_lapic *apic = vcpu->arch.apic; > > > > > > > > > > - if (vector == -1) > > > > > + /* Detect interrupt nesting and disable EOI optimization */ > > > > > + if (pv_eoi_enabled(vcpu) && vector == -2) > > > > > + pv_eoi_clr_pending(vcpu); > > > > > + > > > > > + if (vector < 0) > > > > > > > > With interrupt window exiting, the guest will exit: > > > > > > > > - as soon as it sets RFLAGS.IF=1 and there is any > > > > interrupt pending in IRR. > > > > - any new interrupt is set in IRR will kick vcpu > > > > out of guest mode and recalculate interrupt-window-exiting. > > > > > > > > Doesnt this make this bit unnecessary ? > > > > > > Looks like we could cut it out. But I'm not sure how architectural it is > > > that we exit on interrupt window. > > > I guess there are reasons to exit on interrupt window but > > > isn't it better to make the feature independent of it? > > > > Hum... not sure. Is it helpful for the Hyper-V interface? > > > > > This almost never happens in my testing anyway, so > > > however we handle it is unlikely to affect performance. > > > > It decreases the amount of state that must be maintained. > > > > BTW there is a bug covered by interrupt window exiting: > > > > vcpu0 host > > - irr 5 set > > - isr 5 set, irr 5 cleared > > - eoi_skip bit not set, > > no other bit set in irr. > > - enter guest > > > > irr 4 set > > kick vcpu0 out of guest mode > > > > - eoi pending bit not set > > (previous interrupt injection > > still pending) > > - skip eoi > > > > If it were not for interrupt window exiting, this would > > inject vector 4 on an unrelated exit who knows how long > > in the future. > > > > Also note optimization depends on the fact that the host > > kicks vcpu out unconditionally (so it is dependent on > > certain kvm implementation details). > > > > Look we can summarize as follows: irq windows exit is > required both before and after this patch. > But it does not make the check above redundant. Right, it is not redundant. The above is still a bug: a case where eoi pending bit is not updated properly. How come is this compatible with hyper-v again? Enlight me. -- 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
