Re: [PATCH v3 4/4] platform/x86: intel_tdx_attest: Add TDX Guest attestation interface driver

From: Kai Huang <kai.huang@intel.com>
To: Dave Hansen <dave.hansen@intel.com>,
	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, Hans de Goede <hdegoede@redhat.com>,
	Mark Gross <mgross@linux.intel.com>
Cc: "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>,
	linux-kernel@vger.kernel.org,
	platform-driver-x86@vger.kernel.org
Subject: Re: [PATCH v3 4/4] platform/x86: intel_tdx_attest: Add TDX Guest attestation interface driver
Date: Wed, 20 Apr 2022 11:02:44 +1200	[thread overview]
Message-ID: <79119cc04552617ad462d314dcd8bdbec90a1b20.camel@intel.com> (raw)
In-Reply-To: <ec60ed6f-eafc-80eb-affc-3102c5dc3165@intel.com>

On Tue, 2022-04-19 at 15:49 -0700, Dave Hansen wrote:
> On 4/19/22 15:21, Kai Huang wrote:
> > On Tue, 2022-04-19 at 07:13 -0700, Dave Hansen wrote:
> > > On 4/19/22 00:47, Kai Huang wrote:
> > > > > From security's perspective, attestation is an essential part of TDX.  That
> > > > being said, w/o attestation support in TD guest, I guess nobody will seriously
> > > > use TD guest.
> > > Are you saying you can't think of a single threat model where there's a
> > > benefit to running a TDX guest without attestation?  Will TDX only be
> > > used in environments where secrets are provisioned to guests on the
> > > basis of attestation?
> > > 
> > I don't think anyone should provision secret to a TD before it get attested that
> > it is a genuine TD that he/she expected.  If someone does that, he/she takes the
> > risk of losing the secret.  Of course if someone just want to try a TD then w/o
> > attestation is totally fine.
> 
> Yeah, but you said:
> 
> 	w/o attestation support in TD guest, I guess nobody will
> 	seriously use TD guest.
> 
> I'm trying to get to the bottom of that.  That's a much more broad
> statement than something about when it's safe to deploy secrets.
> 
> There are lots of secrets deployed in (serious) VMs today.  There are
> lots of secrets deployed in (serious) SEV VMs that don't have
> attestation.  Yet, the world somehow hasn't come crashing down.
> 
> I think it's crazy to say that nobody will deploy secrets to TDX VMs
> without attestation.  I think it's a step father into crazy land to say
> that no one will "seriously" use TDX guests without attestation.
> 
> Let's be honest about this and not live in some fantasy world, please.

OK agree.  No argument about this.

-- 
Thanks,
-Kai