From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f199.google.com (mail-pl1-f199.google.com [209.85.214.199]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0BE7938B7D4 for ; Wed, 12 Aug 2026 16:43:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.199 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786553029; cv=none; b=Dy0vUF/PfWCnlBjiowsZUToeJX22GW2zhK+P0P8GG4AkPK6h2y9Yo/NxFBzDKOcPb8U1F/TkMEzhtVcQJ01DQlid0SJSw9O901EJgHtvJ/KtMrHrgHGoEg+sDv3V5NteptcRDnd5GlAKf7KmSzYPRu1htlZa0DsjvhjKK1okS/0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786553029; c=relaxed/simple; bh=qLDEIioUL3e7c7lhtoaFmAMbbGSjhMZuTdeVLqKZKZI=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=OG091HBfzJQU8KNCofj7cB0duLEWj+KfJHfN9M819/mPalh8ECM3lNFbswnptoYNFzWw0HhWn96hcpC5tmHzswnpov0pCymTzAXuqwsAJ6O/LOKEJcRzaX0wyI2YGnfXtolTYChCixclUpOF/r0cCXKkD8mUpp1v7D4aewjQN7c= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=IYtON+bQ; arc=none smtp.client-ip=209.85.214.199 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="IYtON+bQ" Received: by mail-pl1-f199.google.com with SMTP id d9443c01a7336-2ce8a76df2dso19342335ad.2 for ; Wed, 12 Aug 2026 09:43:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1786553027; x=1787157827; darn=vger.kernel.org; h=content-transfer-encoding:content-type:cc:to:from:subject :message-id:references:mime-version:in-reply-to:date:from:to:cc :subject:date:message-id:reply-to:content-type; bh=EVPNR6FWW7kQEwr41zGzOGzrHjzU+yGB7D+zhP7khak=; b=IYtON+bQ46itmarbFu/tTe4EPUMORSev6xJyYjuNuWihTifuFRM3DhiGMEumw9ikow n3dprJ8UFSPYBa+uXDQyZLFKxh976x7dgEga34i5d5FJc4Dq4JPKpiaOIlWaGJdiKO+9 S6ymJ7Cb9i2V6YJnx6d2+xn4Zo/kOw8GBqDXuAz0SFBQF+KnchepqQUZN0WOwyiCq9s+ w3+Pra8CunsG7F/ZjWRNAo8Mpv4zM5F8B9WbSBxCMzVCXK47PSZ6DQblM1kXLOdET89w sCm4F3D2JBUQt9rq9x695OxYttGPJlgyhtb4BKz+DTGa/I3mcS1jQF+ysMhrZdKhR8z0 poAQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1786553027; x=1787157827; h=content-transfer-encoding:content-type:cc:to:from:subject :message-id:references:mime-version:in-reply-to:date :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=EVPNR6FWW7kQEwr41zGzOGzrHjzU+yGB7D+zhP7khak=; b=VgsyGpmT8A7qipW35Q+IU5aK/yCFA1e5Bb793UuSMmUUGyefhP43aZXhPNw1SOMcRa qFRLniTjzDtaqN75Aik2QpKueOyUHkQQWnip3znhCjVPwJ0zo1AP/4T3cAtJI/GdBtQE D4wh3VzRgZSL+rwQAQAhK6yT7p3yxMTMZnALOqN/b0YYU57V0OxhHJwY1lGU2DgiEcxo fIz4A5QEr+6fL0fluvw8baAQ6YX6bFRCB5LCR89KIVjtIADvCMSqMlC3unyQdMJ8Hm0o /5+1BqGhYcoOi61GkSyx2wwwferWUMAdBouR57a+0fzcVPuk9I8vTdo3pu9kpda8NO7p sApA== X-Forwarded-Encrypted: i=1; AHgh+RqqT1hjzsrs882Ccu9O50EZ90Bzl+eqXtytYuvXNvqi0ei5BjomJ63R/71WSUk+VFiGh0Pw6u63qjm5FVU=@vger.kernel.org X-Gm-Message-State: AOJu0YxggA/e28qoG/6e1dk268jLOwrjJJC0WhGd3pkxB/nZckvs/XdK TCasY4U7PJP6WtkmSZr3tGCvMXhgYoP3kl5OZKg/EGFZieTZcO9CDYB/SOvXzoyl40QWCU9sqPi +rN9AGA== X-Received: from plbkr8.prod.google.com ([2002:a17:903:808:b0:2cc:8741:f340]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:903:2cb:b0:2ca:d658:d874 with SMTP id d9443c01a7336-2d345713af3mr80782795ad.23.1786553027152; Wed, 12 Aug 2026 09:43:47 -0700 (PDT) Date: Wed, 12 Aug 2026 09:43:46 -0700 In-Reply-To: <86d532f33816cd4fa3e29c40079a6003abf89324.camel@intel.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260729122939.1340412-1-peter.fang@intel.com> <80b4ea89ebf17398c3bee21d157c7f97ea32aadf.camel@intel.com> <86d532f33816cd4fa3e29c40079a6003abf89324.camel@intel.com> Message-ID: Subject: Re: [PATCH v3 0/4] tdx-guest: Make Quote buffer size dynamic From: Sean Christopherson To: Rick P Edgecombe Cc: "hpa@zytor.com" , Xiaoyao Li , "bp@alien8.de" , "kas@kernel.org" , "binbin.wu@linux.intel.com" , "x86@kernel.org" , "sathyanarayanan.kuppuswamy@linux.intel.com" , "mingo@redhat.com" , "dave.hansen@linux.intel.com" , "linux-kernel@vger.kernel.org" , Artem Bityutskiy , Peter Fang , "tglx@kernel.org" , "linux-coco@lists.linux.dev" , "kvm@vger.kernel.org" Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable On Wed, Aug 12, 2026, Rick P Edgecombe wrote: > On Wed, 2026-08-12 at 07:08 -0700, Sean Christopherson wrote: > > > =C2=A0 |Normal quote=C2=A0=C2=A0=C2=A0 |Migration quote |Report size|= Quote size|uAPI location=C2=A0 | > > > -|----------------|----------------|-----------|----------|----------= -----| > > > 1|Platform scoped |Platform scoped |Grows=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0 |Grows=C2=A0=C2=A0=C2=A0=C2=A0 |TDX host driver| > >=20 > > With my KVM hat on, this option looks very attractive. > >=20 > > And with the caveat that I'm most definitely not an attestation expert,= from a > > separate of concerns perspective, IMO it seems like the report should c= ontain > > the TD-specific information while the quote just wraps that information= in > > platform-specific goo. > >=20 > > In other words, to me, TD-scoped quotes feel like a hack that was throw= n in to > > avoid having to modify the guest because y'all didn't plan ahead. >=20 > Caveman crypto person here too.=C2=A0It seems scattered and makes me simi= larly > suspicious about some lack of planning. But I kind of came to a different > conclusion on what went wrong. >=20 > It seems to me that from the overall solution level, the report should ne= ver > have had the details in it. It should just be some nonce or some type of = thing > that can tie the guest request to the quote that it ends up getting > back.=C2=A0Doesn't it seem weird to get a bunch of details from the TDX m= odule, then > pass them from the guest to host KVM to host userspace then back to the T= DX > module... which already had all those details? Hmm, my mental model of this is that the report contains the "real" payload= , i.e. the metadata describing what is running and whatnot, while the quote effect= ively signs the payload to prove the provenance of the report. That's why I view= the report as TD-specific (what's running) and the quote as platform-specific (= provides root of trust). > My understanding was that the original SGX attestation was a complicator = of the > design of this stuff. Because I'm not sure that SGX had all those details= about > the TD. In fact I can't see how it could have. Is that right Peter? So it= needs > them all to be passed in. All the extra validations etc of this shuffling= is > TDX's problems to deal with, but for Linux, it would be at least a lot le= ss > confusing if there was not two things that have the TD details in them. >=20 > That said, from KVM POV, (1) kicks the attestation out of KVM. I see the > benefit. But a TD quote is a TD scoped operation in concept. To me at lea= st.