On Mon, Oct 14, 2013 at 09:43:04AM +0100, Marc Zyngier wrote: > On 13/10/13 02:09, Christoffer Dall wrote: > > On Tue, Oct 08, 2013 at 06:17:08PM +0100, Marc Zyngier wrote: > >> It appears we have an arbitrary limitation where we refuse to > >> create more than 4 virtual A15 in a single VM. > >> > >> This limitation doesn't make much sense (the number 4 probably > >> comes from the maximum number of CPUs in a A15 cluster, but > >> KVM doesn't have any notion of cluster), and directly > >> contradicts CONFIG_MAX_VCPUS. > > > > So this comes from the early days where I looked at the A15 TRM and the > > MPIDR bit field for the CPU ID is limited to 2 bits. Exactly because > > I wasn't sure what remifications (if any) it would have to start > > populating this register with cluster id = (vcpu_id / 4) and cpu id = > > (vcpu_id % 4) I put this nice arbitrary restriction in there. > > > > I think we need to fix how we show this register to the guest > > otherwise... No? > > I don't see this being an issue, but if we really want to be 100% true > to the A15/A7 TRM, we can always compute MPIDR that way, and adjust > L2CTLR as well. Even with mach-virt we're still pretending to be an A15/A7 right? I think we should adhere to that. Is there some other reason why people shouldn't generally expect MPIDR to be correct (merging this code to KVM and running in a VM notwithstanding)? > > That will require some userspace change in kvmtool though (need to > change the DT generator to cope with the cluster ID). > That would be the less fun part... -Christoffer _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/cucslists/listinfo/kvmarm
