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

[Paolo Bonzini]

On 16/01/21 06:40, Tom Lendacky wrote:
> > Introduce a new Kconfig, AMD_SEV_ES_GUEST, to control the inclusion of
> > support for running as an SEV-ES guest.  Pivoting on AMD_MEM_ENCRYPT for
> > guest SEV-ES support is undesirable for host-only kernel builds as
> > AMD_MEM_ENCRYPT is also required to enable KVM/host support for SEV and
> > SEV-ES.
>
> I believe only KVM_AMD_SEV is required to enable the KVM support to run 
> SEV and SEV-ES guests. The AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT setting is 
> only used to determine whether to enable the KVM SEV/SEV-ES support by 
> default on module load.

Right:

        if (IS_ENABLED(CONFIG_KVM_AMD_SEV) && sev) {
                sev_hardware_setup();
        } else {
                sev = false;
                sev_es = false;
        }

I removed the addition to "config AMD_MEM_ENCRYPT_ from Sean's patch, 
but (despite merging it not once but twice) I don't really like the 
hidden dependency on AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT and thus 
AMD_MEM_ENCRYPT.  Is there any reason to not always enable sev/sev_es by 
default?

Paolo