Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <5905d2772ba3ba015f386787fa0b7a8fade69005.camel@intel.com>
Subject: Re: [PATCH v8 5/5] x86/tdx: Add Quote generation support
From:   Kai Huang <kai.huang@intel.com>
To:     Dave Hansen <dave.hansen@intel.com>,
        Isaku Yamahata <isaku.yamahata@gmail.com>
Cc:     Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@linux.intel.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>, x86@kernel.org,
        "H . Peter Anvin" <hpa@zytor.com>,
        "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
        Tony Luck <tony.luck@intel.com>,
        Andi Kleen <ak@linux.intel.com>,
        Wander Lairson Costa <wander@redhat.com>,
        marcelo.cerri@canonical.com, tim.gardner@canonical.com,
        khalid.elmously@canonical.com, philip.cox@canonical.com,
        linux-kernel@vger.kernel.org
Date:   Mon, 25 Jul 2022 23:05:44 +1200
In-Reply-To: <18578c5a-7a35-ab20-467c-80141b0410a8@intel.com>
References: <20220609025220.2615197-1-sathyanarayanan.kuppuswamy@linux.intel.com>
         <20220609025220.2615197-6-sathyanarayanan.kuppuswamy@linux.intel.com>
         <403cfccb-7fff-ab0b-8ebd-e5b04e631571@intel.com>
         <20220722190524.GA3299911@ls.amr.corp.intel.com>
         <18578c5a-7a35-ab20-467c-80141b0410a8@intel.com>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
User-Agent: Evolution 3.44.3 (3.44.3-1.fc36) 
MIME-Version: 1.0
Precedence: bulk

On Fri, 2022-07-22 at 12:13 -0700, Dave Hansen wrote:
> On 7/22/22 12:05, Isaku Yamahata wrote:
> > > So, the quote portion of this is basically a bidirectional blob sende=
r.
> > >  It's to send a blob between guest userspace to host userspace.
> > >=20
> > > Do we *REALLY* need specific driver functionality for this?  For
> > > instance, is there no existing virtio device that can send blobs back
> > > and forth?
> > It's virtio-vsock.  If virtio-vsock is available, the communication wor=
ks.
> > However, some users would like to disable virtio-vsock on their environ=
ment for
> > some reasons.  Even virtio at all.  Especially for confidential computi=
ng use
> > case.  It's their choice.  It can't be assumed that virtio is available=
.
> >=20
> > The goal is VMM-agnostic (but TDX-specific) interface for that.
>=20
> You're basically saying that every confidential computing technology
> should have its own host user <-> guest kernel <-> guest user ABI.
> That's insanity.  If we do this, we need *one* interface that says "talk
> to the hypervisor" that's common for all hypervisors and hardware
> vendors, or at least more than *one*.
>=20
> We don't need a way to talk to hypervisors for Intel systems and another
> for AMD and yet another on whatever.

Maybe the GetQuote support can be a "Intel driver" with a dedicated Kconfig
option?  Not all customers want it anyway, so having a Kconfig option can a=
lso
reduce code size/attack window.

--=20
Thanks,
-Kai