Re: [PATCH] x86/sev: Add AMD_SEV_ES_GUEST Kconfig for including SEV-ES support

[Sean Christopherson]

On Mon, Jan 18, 2021, Borislav Petkov wrote:
> On Mon, Jan 18, 2021 at 09:32:07PM +0100, Paolo Bonzini wrote:
> > I think it makes sense because AMD_SEV_ES_GUEST's #VC handling is quite a
> > bit of code that you may not want or need.
> 
> Quite a bit of code which ends up practically enabled on the majority of
> distros.
> 
> And it ain't about savings of whopping KiBs. And yet another Kconfig symbol
> in our gazillion Kconfig symbols space means ugly ifdeffery and paying
> attention to randconfig builds.
> 
> For tailored configs you simply disable AMD_MEM_ENCRYPT on !AMD hw and
> all done.

It was the AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT dependency that tripped me up.  To
get KVM to enable SEV/SEV-ES by default, that needs to be enabled, which in turn
requires AMD_MEM_ENCRYPT=y.  I didn't realize that there isn't actually a
dependency on AMD_MEM_ENCRYPT=y

> So I don't see the point for this.

Agreed, I'll send a KVM patch to remove the AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT
dependency.