Re: KVM_SET_CPUID doesn't check supported bits (was Re: [PATCH 0/6] KVM: x86: KVM_SET_SREGS.CR4 bug fixes and cleanup)

[stsp]

07.12.2020 17:09, Paolo Bonzini пишет:
> Il lun 7 dic 2020, 15:04 stsp <stsp2@xxxxxxxxx 
> <mailto:stsp2@xxxxxxxxx>> ha scritto:
>
>     Perhaps it would be good if guest cpuid to
>     have a default values of KVM_GET_SUPPORTED_CPUID,
>     so that the user doesn't have to do the needless
>     calls to just copy host features to guest cpuid.
>
>
> It is too late to change that aspect of the API, unfortunately. We 
> don't know how various userspaces would behave.
Which means some sensible behaviour
already exists if I don't call KVM_SET_CPUID2.
So what is it, #UD on CPUID?
Would be good to have that documented.