On Mon, Jan 11, 2016 at 04:29:03PM +0000, Peter Maydell wrote: > On 11 January 2016 at 16:21, Andrew Jones <drjones@xxxxxxxxxx> wrote: > > On Mon, Jan 11, 2016 at 05:09:27PM +0100, Andrew Jones wrote: > >> On Mon, Jan 11, 2016 at 04:09:29PM +0100, Christoffer Dall wrote: > >> > Are vcpu ids already exposed to userspace (beyond the stupid > >> > KVM_IRQ_LINE) ioctl and as such we're bound to whatever upper limit and > >> > format they have? > >> > >> The only other place I found is KVM_CREATE_VCPU. I suppose we could move > >> to MPIDR for that, and it would be a nice way to handle the "userspace > >> determines MPIDR" work that I plan to do. Both KVM and its userspaces > >> would still use some counter-based vcpu identifiers internally, to avoid > >> large, sparse structures, but I guess the advantage is that they don't > >> have to agree on how they do that. The 'vcpu id' used by KVM_CREATE_VCPU > >> is already 32-bits, and is supposed to be an arbitrary identifier. That > >> all looks good for converting to MPIDR. > >> > > > > Correction. I understand that vcpu-id is "supposed" to be an arbitrary > > identifier now, but it doesn't appear that all the assumptions that it's > > a counter are gone yet... virt/kvm/kvm_main.c has > > > > static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, u32 id) > > ... > > if (id >= KVM_MAX_VCPUS) > > return -EINVAL; > > I think the last time we talked about supporting "userspace > determines MPIDR" the idea was to do it by allowing userspace to > write to the MPIDR register with KVM_SET_ONE_REG. So you'd > create a bunch of CPUs with vcpu-ids as usual, and then the > MPIDRs would be set for them later as appropriate (or not > at all, if userspace was an older qemu). Yup, I recall that. I'm just expanding this discussion into that one. If we wanted to single vcpu identifier type, and we wanted it to be MPIDR, then I guess we'd want to pass it in to KVM_CREATE_VCPU too, at which point we no longer need to set it later with KVM_SET_ONE_REG. Thanks, drew -- 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
