Re: [PATCH 3/3] KVM: TDX: Exit to userspace for GetTdVmCallInfo

[Xiaoyao Li]

On 6/20/2025 8:03 PM, Paolo Bonzini wrote:
> Il ven 20 giu 2025, 03:21 Xiaoyao Li <xiaoyao.li@xxxxxxxxx> ha scritto:
> > >                tdx->vp_enter_args.r11 = 0;
> > > +             tdx->vp_enter_args.r12 = 0;
> > >                tdx->vp_enter_args.r13 = 0;
> > >                tdx->vp_enter_args.r14 = 0;
> > > +             return 1;
> >
> > Though it looks OK to return all-0 for r12 == 0 and undefined case of
> > r12 > 1, I prefer returning TDVMCALL_STATUS_INVALID_OPERAND for
> > undefined case.
>
>
>  From the GHCI I wasn't sure that TDVMCALL_STATUS_INVALID_OPERAND is a
> valid result at all.

It's part of the new GHCI change, which currently is still in draft 
state. (Sorry for not informing you)

The proposed GHCI update defines VMCALL_OPERAND_INVALID for the case of 
input R12 value is not supported. So for VMM that doesn't implement the 
enumeration for the optional leafs when r12 = 1 can return this status 
code. As well, VMM can return this status code for the case of input R12 
>= 2, to avoid the VMM introduces its own defined behavior.

> Paolo
>
> > So please make above "case 0:", and make the "default:" return
> > TDVMCALL_STATUS_INVALID_OPERAND
> >
> > >        }
> > > -     return 1;
> > >    }
> > >
> > >    static int tdx_complete_simple(struct kvm_vcpu *vcpu)
> > > diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> > > index 6708bc88ae69..fb3b4cd8d662 100644
> > > --- a/include/uapi/linux/kvm.h
> > > +++ b/include/uapi/linux/kvm.h
> > > @@ -461,6 +461,11 @@ struct kvm_run {
> > >                                        __u64 gpa;
> > >                                        __u64 size;
> > >                                } get_quote;
> > > +                             struct {
> > > +                                     __u64 ret;
> > > +                                     __u64 leaf;
> > > +                                     __u64 r11, r12, r13, r14;
> > > +                             } get_tdvmcall_info;
> > >                        };
> > >                } tdx;
> > >                /* Fix the size of the union. */