2016-02-12 16:38+0100, Paolo Bonzini: > On 12/02/2016 14:59, Suravee Suthikulpanit wrote: >> + case AVIC_INCMP_IPI_ERR_TARGET_NOT_RUN: >> + kvm_lapic_reg_write(apic, APIC_ICR2, icrh); >> + kvm_lapic_reg_write(apic, APIC_ICR, icrl); > > Wouldn't this cause a double injection of the IPI if the following happens: I think it will. (IRR was written to APIC pages, so hypervisor's only job is to make sure that all targeted VCPUs eventually run.) > The handling of races for IsRunning and incomplete IPIs has always been > very confusing to me whenever I read the AVIC specification. It would > be great if you could clarify this. Yeah, we bug there as well: If all target VCPUs have IsRunning set and are in the process of being scheduled out (avic_set_running false), then there is no VMEXIT on IPI and the doorbell does nothing[1]; KVM desn't re-check pending interrupts before actually scheduling out, therefore VCPUs will wake only if another interrupt comes. The hypervisor can manage the IsRunning as it wishes to, so KVM probably should set IsRunning to false before scanning IRR. --- 1: I didn't find a single mention of a situation when doorbell arrives outside of guest mode, so I presume that nothing happens. Is it right? Thanks. -- 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
