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

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Message-ID: <79119cc04552617ad462d314dcd8bdbec90a1b20.camel@intel.com>
Date:   Wed, 20 Apr 2022 11:02:44 +1200
From:   Kai Huang <kai.huang@...el.com>
To:     Dave Hansen <dave.hansen@...el.com>,
        Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        Hans de Goede <hdegoede@...hat.com>,
        Mark Gross <mgross@...ux.intel.com>
Cc:     "H . Peter Anvin" <hpa@...or.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Tony Luck <tony.luck@...el.com>,
        Andi Kleen <ak@...ux.intel.com>, linux-kernel@...r.kernel.org,
        platform-driver-x86@...r.kernel.org
Subject: Re: [PATCH v3 4/4] platform/x86: intel_tdx_attest: Add TDX Guest
 attestation interface driver

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