Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:18 as permitted sender) client-ip=2620:137:e000::1:18;
Date:   Thu, 7 Apr 2022 22:34:57 -0700
From:   Isaku Yamahata <isaku.yamahata@gmail.com>
To:     Paolo Bonzini <pbonzini@redhat.com>
Cc:     Sagi Shahar <sagis@google.com>,
        "Yamahata, Isaku" <isaku.yamahata@intel.com>, kvm@vger.kernel.org,
        linux-kernel@vger.kernel.org, isaku.yamahata@gmail.com,
        Jim Mattson <jmattson@google.com>,
        Erdem Aktas <erdemaktas@google.com>,
        Connor Kuehl <ckuehl@redhat.com>,
        Sean Christopherson <seanjc@google.com>
Subject: Re: [RFC PATCH v5 083/104] KVM: x86: Split core of hypercall
 emulation to helper function
Message-ID: <20220408053457.GA857847@ls.amr.corp.intel.com>
References: <cover.1646422845.git.isaku.yamahata@intel.com>
 <f3293bd872a916bf33165a2ec0d6fc50533b817f.1646422845.git.isaku.yamahata@intel.com>
 <CAAhR5DFPsmxYXXXZ9WNW=MDWRRz5jrntPvsnKw7VTrRh5CbohQ@mail.gmail.com>
 <1eac9040-f75f-8838-bd75-521cb666c61a@redhat.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
In-Reply-To: <1eac9040-f75f-8838-bd75-521cb666c61a@redhat.com>
Precedence: bulk

On Thu, Apr 07, 2022 at 03:12:57PM +0200,
Paolo Bonzini <pbonzini@redhat.com> wrote:

> > > +       if (static_call(kvm_x86_get_cpl)(vcpu) != 0) {
> > > +               ret = -KVM_EPERM;
> > > +               goto out;
> > > +       }
> 
> Is this guaranteed by TDG.VP.VMCALL?

Yes. TDCALL instruction in TD results in #GP(0) if CPL > 0.
It's documented in trust domain CPU architectural extensions spec.
https://www.intel.com/content/dam/develop/external/us/en/documents-tps/intel-tdx-cpu-architectural-specification.pdf

Anyway VMM can't know TD guest CPL (or other CPU state).
-- 
Isaku Yamahata <isaku.yamahata@gmail.com>