On Sat, Mar 14, 2015 at 06:00:15PM -0600, James Sullivan wrote: > This series of patches extends the KVM interrupt delivery mechanism > to correctly account for the MSI Redirection Hint bit. The RH bit is > used in logical destination mode to indicate that the delivery of the > interrupt shall only be to the lowest priority candidate LAPIC. > > Currently, there is no handling of the MSI RH bit in the KVM interrupt > delivery mechanism. This patch implements the following logic: > > * DM=0, RH=* : Physical destination mode. Interrupt is delivered to > the LAPIC with the matching APIC ID. (Subject to > the usual restrictions, i.e. no broadcast dest) > * DM=1, RH=0 : Logical destination mode without redirection. Interrupt > is delivered to all LAPICs in the logical group > specified by the IRQ's destination map and delivery > mode. "When RH is 0, the interrupt is directed to the processor listed in the Destination ID field." > * DM=1, RH=1 : Logical destination mode with redirection. Interrupt > is delivered only to the lowest priority LAPIC in the > logical group specified by the dest map and the > delivery mode. Delivery semantics are otherwise > specified by the delivery_mode of the IRQ, which > is unchanged. > > In other words, the RH bit is ignored in physical destination mode, and > when it is set in logical destination mode causes delivery to only apply > to the lowest priority processor in the logical group. The IA32 manual > is in slight contradiction with itself on this matter, but this patch > agrees with this interpretation of the RH bit: > > https://software.intel.com/en-us/forums/topic/288883 > > This patch has passed some rudimentary tests using an SMP QEMU guest and > virtio sourced MSIs, but I haven't done experiments with passing through > PCI hardware (intend to start working on this). > > Let me know your thoughts. > > -James > > -- > 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 -- 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
