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Date: Tue, 9 Apr 2024 08:26:28 -0700
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Subject: Re: [PATCH v5 07/17] KVM: x86: add fields to struct kvm_arch for CoCo features
From: Sean Christopherson <seanjc@google.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Rick P Edgecombe <rick.p.edgecombe@intel.com>, "kvm@vger.kernel.org" <kvm@vger.kernel.org>, 
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, 
	"michael.roth@amd.com" <michael.roth@amd.com>, Isaku Yamahata <isaku.yamahata@intel.com>
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On Tue, Apr 09, 2024, Paolo Bonzini wrote:
> On Tue, Apr 9, 2024 at 3:21=E2=80=AFAM Sean Christopherson <seanjc@google=
com> wrote:
> > > I'm a little late to this conversation, so hopefully not just complic=
ating
> > > things. But why not deduce has_private_mem and has_protected_state fr=
om the
> > > vm_type during runtime? Like if kvm.arch.vm_type was instead a bit ma=
sk with
> > > the bit position of the KVM_X86_*_VM set, kvm_arch_has_private_mem() =
could
> > > bitwise-and with a compile time mask of vm_types that have primate me=
mory.
> > > This also prevents it from ever transitioning through non-nonsensical=
 states
> > > like vm_type =3D=3D KVM_X86_TDX_VM, but !has_private_memory, so would=
 be a little
> > > more robust.
> >
> > LOL, time is a circle, or something like that.  Paolo actually did this=
 in v2[*],
> > and I objected, vociferously.
>=20
> To be fair, Rick is asking for something much less hideous - just set
>=20
>  kvm->arch.vm_type =3D (1 << vm_type);
>=20
> and then define kvm_has_*(kvm) as !!(kvm->arch.vm_type & SOME_BIT_MASK).
>=20
> And indeed it makes sense as an alternative.

Ah, yeah, I'd be fine with that.=20

> It also feels a little bit more restrictive and the benefit is small, so =
I
> think I'm going to go with this version.

+1