Re: [PATCH v3 2/2] target/arm/kvm: add kvm-psci-version vcpu property

[Eric Auger <eric.auger@redhat.com>]

On 11/13/25 1:05 PM, Sebastian Ott wrote:
> Hi Philippe,
>
> On Wed, 12 Nov 2025, Philippe Mathieu-Daudé wrote:
>> On 12/11/25 19:13, Sebastian Ott wrote:
>>>  Provide a kvm specific vcpu property to override the default
>>>  (as of kernel v6.13 that would be PSCI v1.3) PSCI version emulated
>>>  by kvm. Current valid values are: 0.1, 0.2, 1.0, 1.1, 1.2, and 1.3
>>>
>>>  Note: in order to support PSCI v0.1 we need to drop vcpu
>>>  initialization with KVM_CAP_ARM_PSCI_0_2 in that case.
>>>
>>>  Signed-off-by: Sebastian Ott <sebott@redhat.com>
>>>  ---
>>>    docs/system/arm/cpu-features.rst |  5 +++
>>>    target/arm/cpu.h                 |  6 +++
>>>    target/arm/kvm.c                 | 64
>>> +++++++++++++++++++++++++++++++-
>>>    3 files changed, 74 insertions(+), 1 deletion(-)
>>
>>
>>>  diff --git a/target/arm/kvm.c b/target/arm/kvm.c
>>>  index 0d57081e69..e91b1abfb8 100644
>>>  --- a/target/arm/kvm.c
>>>  +++ b/target/arm/kvm.c
>>>  @@ -484,6 +484,49 @@ static void kvm_steal_time_set(Object *obj, bool
>>>  value, Error **errp)
>>>        ARM_CPU(obj)->kvm_steal_time = value ? ON_OFF_AUTO_ON :
>>>    ON_OFF_AUTO_OFF;
>>>    }
>>>
>>>  +struct psci_version {
>>>  +    uint32_t number;
>>>  +    const char *str;
>>>  +};
>>>  +
>>>  +static const struct psci_version psci_versions[] = {
>>>  +    { QEMU_PSCI_VERSION_0_1, "0.1" },
>>>  +    { QEMU_PSCI_VERSION_0_2, "0.2" },
>>>  +    { QEMU_PSCI_VERSION_1_0, "1.0" },
>>>  +    { QEMU_PSCI_VERSION_1_1, "1.1" },
>>>  +    { QEMU_PSCI_VERSION_1_2, "1.2" },
>>>  +    { QEMU_PSCI_VERSION_1_3, "1.3" },
>>>  +    { -1, NULL },
>>>  +};
>>
>>
>>>  @@ -505,6 +548,12 @@ void kvm_arm_add_vcpu_properties(ARMCPU *cpu)
>>>                                 kvm_steal_time_set);
>>>        object_property_set_description(obj, "kvm-steal-time",
>>>                                        "Set off to disable KVM steal
>>>  time.");
>>>  +
>>>  +    object_property_add_str(obj, "kvm-psci-version",
>>>  kvm_get_psci_version,
>>>  +                            kvm_set_psci_version);
>>>  +    object_property_set_description(obj, "kvm-psci-version",
>>>  +                                    "Set PSCI version. "
>>>  +                                    "Valid values are 0.1, 0.2,
>>> 1.0, 1.1,
>>>  1.2, 1.3");
>>
>> Could we enumerate from psci_versions[] here?
>>
>
> Hm, we'd need to concatenate these. Either manually:
> "Valid values are " psci_versions[0].str ", " psci_versions[1].str ",
> " ... which is not pretty and still needs to be touched for a new
> version.
>
> Or by a helper function that puts these in a new array and uses smth like
> g_strjoinv(", ", array);
> But that's quite a bit of extra code that needs to be maintained without
> much gain.
>
> Or we shy away from the issue and rephrase that to:
> "Valid values include 1.0, 1.1, 1.2, 1.3" 
Personally I would vote for keeping it as is (by the way why did you
moit 0.1 and 0.2 above?)

Eric
>
> Since the intended use case is via machine types and I don't expect a
> lot of users setting the psci version manually - I vote for option 3.
>
> Opinions?
>
> Sebastian