Re: [PATCH v2 04/11] KVM: SEV: publish supported VMSA features

[Paolo Bonzini]

On 2/23/24 17:07, Sean Christopherson wrote:
> > diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> > index f760106c31f8..53e958805ab9 100644
> > --- a/arch/x86/kvm/svm/sev.c
> > +++ b/arch/x86/kvm/svm/sev.c
> > @@ -59,10 +59,12 @@ module_param_named(sev_es, sev_es_enabled, bool, 0444);
> >   /* enable/disable SEV-ES DebugSwap support */
> >   static bool sev_es_debug_swap_enabled = true;
> >   module_param_named(debug_swap, sev_es_debug_swap_enabled, bool, 0444);
> > +static u64 sev_supported_vmsa_features;
> >   #else
> >   #define sev_enabled false
> >   #define sev_es_enabled false
> >   #define sev_es_debug_swap_enabled false
> > +#define sev_supported_vmsa_features 0
>
> Ok, I've reached my breaking point.  Compiling sev.c for CONFIG_KVM_AMD_SEV=n is
> getting untenable.  Splattering #ifdefs _inside_ SEV specific functions is weird
> and confusing.

Ok, I think in some cases I prefer stubs but I'll weave your 4 patches 
in v3.

Paolo

> And unless dead code elimination isn't as effective as I think it is, we don't
> even need any stuba  since sev_guest() and sev_es_guest() are __always_inline
> specifically so that useless code can be elided.  Or if we want to avoid use of
> IS_ENABLED(), we could add four stubs, which is still well worth it.
>
> Note, I also have a separate series that I will post today (I hope) that gives
> __svm_sev_es_vcpu_run() similar treatment (the 32-bit "support" in assembly is
> all kinds of stupid).
>
> Attached patches are compile-tested only, though I'll try to take them for a spin
> on hardware later today.