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

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Message-ID: <CABgObfaeYdKeYQb+6j6j6u5ytasgb=t2z03cQvkG2c+owfOCgg@mail.gmail.com>
Date: Fri, 20 Jun 2025 14:03:49 +0200
From: Paolo Bonzini <pbonzini@...hat.com>
To: Xiaoyao Li <xiaoyao.li@...el.com>
Cc: "Kernel Mailing List, Linux" <linux-kernel@...r.kernel.org>, kvm <kvm@...r.kernel.org>, 
	Sean Christopherson <seanjc@...gle.com>, Rick Edgecombe <rick.p.edgecombe@...el.com>, 
	"Huang, Kai" <kai.huang@...el.com>, Adrian Hunter <adrian.hunter@...el.com>, reinette.chatre@...el.com, 
	"Lindgren, Tony" <tony.lindgren@...el.com>, "Yamahata, Isaku" <isaku.yamahata@...el.com>, 
	Yan Zhao <yan.y.zhao@...el.com>, mikko.ylinen@...ux.intel.com, 
	"Shutemov, Kirill" <kirill.shutemov@...el.com>, "Yao, Jiewen" <jiewen.yao@...el.com>, 
	Binbin Wu <binbin.wu@...ux.intel.com>
Subject: Re: [PATCH 3/3] KVM: TDX: Exit to userspace for GetTdVmCallInfo

Il ven 20 giu 2025, 03:21 Xiaoyao Li <xiaoyao.li@...el.com> 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.

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. */
>