Re: [PATCH] KVM: arm64: Bump KVM_VCPU_MAX_FEATURES
From: Steven Price
Date: Wed Nov 27 2024 - 10:24:45 EST
On 27/11/2024 15:16, Marc Zyngier wrote:
> On Wed, 27 Nov 2024 14:56:31 +0000,
> Steven Price <steven.price@xxxxxxx> wrote:
>>
>> When the KVM_ARM_VCPU_HAS_EL2 define was added, the value of
>> KVM_VCPU_MAX_FEATURES wasn't incremented, so that feature has never been
>> in the KVM_VCPU_VALID_FEATURES bit mask. This means the HAS_EL2 feature
>> will never be exposed to user space even if the system supports it.
>>
>> Fixes: 89b0e7de3451 ("KVM: arm64: nv: Introduce nested virtualization VCPU feature")
>> Signed-off-by: Steven Price <steven.price@xxxxxxx>
>> ---
>> I might be missing something, and it's possible that
>> KVM_ARM_VCPU_HAS_EL2 is deliberately not exposed yet.
>
> This is on purpose. I'm not planning to enable EL2 support until it is
> ready.
I did suspect that's the case - but it might have been better to knobble
it in system_supported_vcpu_features()/kvm_vcpu_init_check_features()
rather than 'hiding' it in the MAX_FEATURES. But hindsight is a
wonderful thing ;)
>> However I'm
>> working on v6 of the host CCA series and as part of that want to add a
>> new feature but and bump KVM_VCPU_MAX_FEATURES up to 9.
>
> Well, I guess that defines some ordering then! :D
Indeed - I'll try to remember to include note about this "dependency" in
my cover letter. We're likely to need a few more rounds for CCA to be
ready, so hopefully NV will naturally be there in time :D
Thanks,
Steve