Re: [PATCH v11 025/113] KVM: TDX: Use private memory for TDX

[Huang, Kai]

On Tue, 2023-01-17 at 16:40 +0000, Sean Christopherson wrote:
> On Mon, Jan 16, 2023, Huang, Kai wrote:
> > On Thu, 2023-01-12 at 08:31 -0800, isaku.yamahata@xxxxxxxxx wrote:
> > > From: Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx>
> > > 
> > > Override kvm_arch_has_private_mem() to use fd-based private memory.
> > > Return true when a VM has a type of KVM_X86_TDX_VM.
> > > 
> > > Signed-off-by: Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx>
> > > Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
> > > ---
> > >  arch/x86/kvm/x86.c | 5 +++++
> > >  1 file changed, 5 insertions(+)
> > > 
> > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> > > index d548d3af6428..a8b555935fd8 100644
> > > --- a/arch/x86/kvm/x86.c
> > > +++ b/arch/x86/kvm/x86.c
> > > @@ -13498,6 +13498,11 @@ int kvm_sev_es_string_io(struct kvm_vcpu *vcpu, unsigned int size,
> > >  }
> > >  EXPORT_SYMBOL_GPL(kvm_sev_es_string_io);
> > >  
> > > +bool kvm_arch_has_private_mem(struct kvm *kvm)
> > > +{
> > > +	return kvm->arch.vm_type == KVM_X86_TDX_VM;
> > > +}
> > > +
> > 
> > AMD's series has a different solution:
> > 
> > https://lore.kernel.org/lkml/20221214194056.161492-3-michael.roth@xxxxxxx/
> > 
> > I think somehow this needs to get aligned.
> 
> Ya.  My thought is
> 
>  bool kvm_arch_has_private_mem(struct kvm *kvm)
>  {
> 	return kvm->arch.vm_type != KVM_X86_DEFAULT_VM;
>  }
> 
> where the VM types end up being:
> 
>  #define KVM_X86_DEFAULT_VM	0
>  #define KVM_X86_PROTECTED_VM	1
>  #define KVM_X86_TDX_VM		2
>  #define KVM_X86_SNP_VM		3

What's the  difference between  PROTECTED_VM vs TDX_VM/SNP_VM, may I ask?

> 
> Don't spend too much time reworking the TDX series at this point, I'm going to do
> a trial run of combining UPM+TDX+SNP sometime in the next few weeks to see how all
> the pieces fit together, this is one of the common touchpoints that I'll make sure
> to look at.  Though if you have ideas on, by all means post them.

Glad to know.  Thanks for your time.