Re: [PATCH v4 2/2] target/arm/kvm: add kvm-psci-version vcpu property

[Sebastian Ott <sebott@redhat.com>]

On Wed, 11 Feb 2026, Peter Maydell wrote:
> On Wed, 11 Feb 2026 at 15:37, Sebastian Ott <sebott@redhat.com> wrote:
>>
>> Hi Peter,
>>
>> On Fri, 6 Feb 2026, Peter Maydell wrote:
>>> On Tue, 2 Dec 2025 at 16:09, Sebastian Ott <sebott@redhat.com> wrote:
>
>>>> +static char *kvm_get_psci_version(Object *obj, Error **errp)
>>>> +{
>>>> +    ARMCPU *cpu = ARM_CPU(obj);
>>>> +    const struct psci_version *ver;
>>>> +
>>>> +    for (ver = psci_versions; ver->number != -1; ver++) {
>> [...]
>>>> +        if (ver->number == cpu->psci_version)
>>>> +            return g_strdup(ver->str);
>>>> +    }
>>>> +
>>>> +    return g_strdup_printf("Unknown PSCI-version: %x", cpu->psci_version);
>>>
>>> Is this ever possible?
>>
>> Hm, not sure actually - what if there's a new kernel/qemu implementing
>> psci version 1.4 and then you migrate to a qemu that doesn't know about
>> 1.4?
>
> Oh, I see -- we're reporting back cpu->psci_version here, which
> indeed could be the value set by KVM. I misread and assumed
> this was just reading back the field that the setter sets,
> which is kvm_prop_psci_version (and which I think will only
> be set via the setter and so isn't ever a value the setter
> doesn't know about).
>
> That does flag up a bug in this patch, though: if I set
> a QOM property via the setter function and then read its
> value via the getter function I ought to get back what
> I just wrote.
>

Meaning this should be something like below?

static char *kvm_get_psci_version(Object *obj, Error **errp)
{
     ARMCPU *cpu = ARM_CPU(obj);

     return g_strdup_printf("%d.%d",
 	(int) PSCI_VERSION_MAJOR(cpu->kvm_prop_psci_version),
 	(int) PSCI_VERSION_MINOR(cpu->kvm_prop_psci_version));
}