Re: [Qemu-devel] [PATCH v5 11/17] target-s390x: Add KVM VM attribute interface for S390 CPU models

[Michael Mueller <mimu@linux.vnet.ibm.com>]

On Mon, 27 Apr 2015 12:52:54 +0200
Christian Borntraeger <borntraeger@de.ibm.com> wrote:

> Am 27.04.2015 um 11:43 schrieb Michael Mueller:
> > On Mon, 27 Apr 2015 10:15:47 +0200
> > Christian Borntraeger <borntraeger@de.ibm.com> wrote:
> > 
> >> Am 13.04.2015 um 15:56 schrieb Michael Mueller:
> >> [...]
> >>> +static int cpu_model_get(KVMState *s, uint64_t attr, uint64_t addr)
> >>> +{
> >>> +    int rc = -ENOSYS;
> >>> +    struct kvm_device_attr dev_attr = {
> >>> +        .group = KVM_S390_VM_CPU_MODEL,
> >>> +        .attr = attr,
> >>> +        .addr = addr,
> >>
> >> Would it make sense to do the cast here....
> > 
> > cpu_model_get/set() is used to handle both attributes,
> > KVM_S390_VM_CPU_MACHINE and KVM_S390_VM_CPU_PROCESSOR.
> > Both require a different type in the signature, (S390ProcessorProps*)
> > and (S390MachineProps*). Adding both as parameters seems to be odd
> > and would require additionally logic in the function.
> > Thus I think doing the cast outside is just the right thing to do.
> 
> So what about a void pointer then as parameter?
> I prefer a pointer for qemu process memory over uint64_t as part of the 
> function interface. This makes it somewhat clearer that this is an
> address within QEMU. Both ways will certainly work, though.

The interface calls are:

int kvm_s390_get_machine_props(KVMState *s, S390MachineProps *prop)
int kvm_s390_get_processor_props(S390ProcessorProps *prop)

cpu_model_get/set() are just static helpers.

> 
> Conny, I guess you will pick up the patches. Any preference?
> 
> Christian