On 03/20/2015 09:22 AM, James Sullivan wrote: > On 03/20/2015 09:15 AM, Radim Krčmář wrote: >> 2015-03-19 16:51-0600, James Sullivan: >>> I played around with native_compose_msi_msg and discovered the following: >>> >>> * dm=0, rh=0 => Physical Destination Mode >>> * dm=0, rh=1 => Failed delivery >>> * dm=1, rh=0 => Logical Destination Mode, No Redirection >>> * dm=1, rh=1 => Logical Destination Mode, Redirection >> >> Great! (What CPU family was that?) >> > > This was on Intel x86_64 (Core i5-3210m, 'Ivy Bridge'). > >>> So it seems to be the case that logical destination mode is used whenever >>> DM=1, regardless of RH. Furthermore, the case where DM=0 and RH=1 is >>> undefined, as was indicated in the closing response to the thread in >>> https://software.intel.com/en-us/forums/topic/288883 : >> >> DM=0+RH=1 might be defined to "fail", but I think it's acceptable to >> treat it as undefined. (Deliver them in KVM if it improves something.) >> > > My thoughts as well. > >> I'm still wondering about last sentence from that link, the >> parenthesised part to be exact, >> The reference to the APIC ID being 0xff is because 0xff is broadcast >> and lowest priority (what the RH bit really is for X86) is illegal >> with broadcast. >> >> Can you also check if RH=1 does something to delivery mode? >> >> Thanks. >> > > Sure, I'll look into that as well. > > -James > I haven't seen any changes in the MSI Data Register for any values of RH, but I don't have a great sample size (one machine with one set of PCI devices), so if anyone else can confirm that I would appreciate it. Worth noting that low prio delivery was used across the board for my PCI devices regardless of RH=1 or 0, so it doesn't seem to be de facto the case that the RH bit's only purpose is for lowprio delivery on x86. Again, need to have some more PCI devices to test against to confirm anything. -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
