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

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Date: Fri, 23 Feb 2024 09:01:44 -0800
From: Sean Christopherson <seanjc@...gle.com>
To: Paolo Bonzini <pbonzini@...hat.com>
Cc: linux-kernel@...r.kernel.org, kvm@...r.kernel.org, michael.roth@....com, 
	aik@....com
Subject: Re: [PATCH v2 04/11] KVM: SEV: publish supported VMSA features

On Fri, Feb 23, 2024, Paolo Bonzini wrote:
> 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.

No problem, I don't have a strong preference.  I initially added stubs instead of
the IS_ENABLED().  The main reason I switched is when I realized that sev_set_cpu_caps()
*cleared* capabilities, and so decided it would be safer to have a separate patch
that effectively stubbed out the global SEV calls.