On 03/11/2015 07:43 AM, Radim Krčmář wrote: > 2015-03-10 16:39-0600, James Sullivan: >> On 03/10/2015 08:47 AM, Radim Krčmář wrote: >>>> + irq->dest_mode = phys ? 0 : (MSI_ADDR_DEST_MODE_LOGICAL); >>> >>> (Should be APIC_DEST_LOGICAL. All works because it is a boolean and we >>> only checked for APIC_DEST_PHYSICAL, which is 0.) >>> >> >> Thank you, that should be as follows: >> irq->dest_mode = phys ? (APIC_DEST_PHYSICAL) : (APIC_DEST_LOGICAL); >> ? > > Yes, thanks. (No need for parentheses around macros, we "agreed" to > cover that in definition and they don't make this more readable.) > I'll tidy that up too. > Your patch improves the situation, but removing the TODO is not > warranted -- RH still doesn't do what it should: > >>> How does DM=1/RH=1 work on real hardware? >>> (There seem to be interesting corner cases with irq->delivery_mode like >>> APIC_DM_NMI.) >> >> The IA32 manual says that if DM=1/RH=1, we operate in logical destination mode >> similarly to other IPIs. I don't believe this patch introduces any invalid >> settings listed in section 10-21, Vol. 3, so this shouldn't create any weirdness. > > Quoting SDM Jan 2015, 10.11.1 Message Address Register Format: > This bit [RH] indicates whether the message should be directed to the > processor with the lowest interrupt priority among processors that can > receive the interrupt. > > => it should behave like lowest priority delivery. > Deliver to just one APIC -- we don't do that. > > KVM interrupt delivery functions can only specify lowest priority though > delivery_mode and we would have to rework KVM if MSI can set something > else in the delivery_mode (like NMI). > I see-- That will pose issues when you want some particular semantics of one delivery mode (such as ignoring vector info in NMI) but want low-pri delivery. Short of writing an MSI specific delivery function and calling it in kvm_set_msi, I can't think of a way to get this. Do you think that's warranted? I'll document this and resubmit this patch with the TODO for now. Thanks for the insight. -- 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
