On 14/03/16 18:20, Andre Przywara wrote: > Hi, > > On 14/03/16 17:54, Marc Zyngier wrote: >> On 14/03/16 17:29, Peter Maydell wrote: >>> On 14 March 2016 at 11:13, Andre Przywara <andre.przywara@xxxxxxx> wrote: >>>> So I see two ways to fix this: >>>> 1.) we find a KVM specific way of letting userland save and restore the >>>> ITS tables directly >>>> 2.) we implement the BASER<n> registers, but still use our "cache" for >>>> normal operations. On demand we would serialize KVM's virtual ITS data >>>> structures and put them into the guest's memory, so they could be >>>> saved/restored from there. >>> >>> I feel like we're rehashing a bunch of design choices we talked >>> through way back in the last-but-one Connect. I don't suppose >>> anybody wrote down our rationales from back then? >>> >>> (In particular I forget whether we decided the ITS tables were >>> large enough to need to allow some sort of before-the-VM-stops >>> migration of the data, which would be relatively doable with >>> option 2 but painful under option 1.) >> >> I think only option 2 is valid here, and we must be able to shove most >> of the routing information in the device/collection/IT tables. Common HW >> seems to use 64bit of data per entry per table, so we should be able to >> do the same with KVM. > > All right, just skimmed over this and it looks doable. > For the collection table we will most likely even get away with 32 bits > per entry (compressed MPIDR or even VCPUIDs). > Would the IPA of the ITTE suffice for each device table entry? Yup. You can even loose the low 8 bits, as this is guaranteed to be 256 byte aligned. So for a 48bit IPA and 32bit of EventID, you end up only using 45 bits, which leaves quite a few to spare, should we ever want a larger IPA. Ideally, this should contain the relevant fields of the MAPD command, with similar sizes. Thanks, M. -- Jazz is not dead. It just smells funny... -- 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
