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;
Date:   Tue, 8 Aug 2023 11:17:33 -0700
From:   Dan Williams <dan.j.williams@intel.com>
To:     Dionna Amalie Glaze <dionnaglaze@google.com>,
        Dan Williams <dan.j.williams@intel.com>
CC:     Sathyanarayanan Kuppuswamy 
        <sathyanarayanan.kuppuswamy@linux.intel.com>,
        James Bottomley <James.Bottomley@hansenpartnership.com>,
        <dhowells@redhat.com>, Brijesh Singh <brijesh.singh@amd.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Tom Lendacky <thomas.lendacky@amd.com>,
        "Borislav Petkov" <bp@alien8.de>,
        Jarkko Sakkinen <jarkko@kernel.org>,
        Samuel Ortiz <sameo@rivosinc.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "Andrew Morton" <akpm@linux-foundation.org>,
        <linux-coco@lists.linux.dev>, <keyrings@vger.kernel.org>,
        <x86@kernel.org>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 0/4] keys: Introduce a keys frontend for attestation
 reports
Message-ID: <64d286bda1d8b_5ea6e294eb@dwillia2-xfh.jf.intel.com.notmuch>
References: <c6576d1682b576ba47556478a98f397ed518a177.camel@HansenPartnership.com>
 <64cdb5f25c56_2138e294f1@dwillia2-xfh.jf.intel.com.notmuch>
 <1180481830431165d49c5e64b92b81c396ebc9b1.camel@HansenPartnership.com>
 <64d17f5728fbc_5ea6e2943f@dwillia2-xfh.jf.intel.com.notmuch>
 <c7d6e953a4b36014ea0c7406531b24bb29d6127e.camel@HansenPartnership.com>
 <2425e00b-defb-c12b-03e5-c3d23b30be01@linux.intel.com>
 <64d263e44e401_2138e29486@dwillia2-xfh.jf.intel.com.notmuch>
 <CAAH4kHamob7g_+BRd0JW76cM7_vS=jzXzRjrgCPDxZ29VnzdCQ@mail.gmail.com>
 <64d270a2a68ce_5ea6e294f0@dwillia2-xfh.jf.intel.com.notmuch>
 <CAAH4kHYht5s4CkS5Y9+VotPH4WqDrzng0vYy89oq0_U16H_dDA@mail.gmail.com>
Content-Type: text/plain; charset="us-ascii"
Content-Disposition: inline
In-Reply-To: <CAAH4kHYht5s4CkS5Y9+VotPH4WqDrzng0vYy89oq0_U16H_dDA@mail.gmail.com>
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?pn8yJT6J1dIykYoaVuuFWoleX3jjYVPwaEuVfok1fuHBcive+X4I9ueL5nww?=
 =?us-ascii?Q?KVvqCUwqQMn4s2TFHNiMSiouZa1eTU9YCoWBnucYbQ0O/U+pfpYkvf0HSxNd?=
 =?us-ascii?Q?4COhUK6DKoa6xlZXpmOrJGGV5mPz+LEOgrKYGQ6z1a2Z9gxu94yfiAGEhGgv?=
 =?us-ascii?Q?GHY+/InR3YdWrNHsGtL20Mfmt/FlHeAUtvqAubTM5lf3p35jJkivYBGjd4gZ?=
 =?us-ascii?Q?iNuR0j/TjEuDMVHVd6ZVqYLmanph/9bdAKKzyqi63WHXo9kTz6VFwe59Tv+b?=
 =?us-ascii?Q?tZwslVNZI/+cyfbXehOJcBNXZP3xj9PBHE8QRtu3BFqB1aPvGfSWgM5jJSm/?=
 =?us-ascii?Q?ut6+tLBIRZVPrQTEGqOWfyCFk2dBixY3UM1JqXCV3i3lFJQ7VldVZAMicMZ5?=
 =?us-ascii?Q?e6WYFjkeIa3iecWys/c5ljsqlLC/x91QuCBn3mPPGdZyRw9JpmYW04UoBkXC?=
 =?us-ascii?Q?gB28iGZn9otKs0fU7KwhAflUr3zQexiQwdo8cld80EpQRJxUvj2YMfoDmQ4q?=
 =?us-ascii?Q?vhBKvO+kU4BVsxanIDx7jZFgGNvPdR+iiIqOBBbQhHL44SZyWoqW/rBz1kUe?=
 =?us-ascii?Q?5CVPnVKQJKpdXhmgQsjEC4N8TzBy9EsmvOKG+8emED+TiOEJcMvIy5azTOH/?=
 =?us-ascii?Q?fM2i+0MiD4d7obPyjL8ufPb7Z7FcElohszKfEW7eI1TSBvSytzh7dSiGM9kV?=
 =?us-ascii?Q?1lc7Q64eDvymYM4Vy2ZGKqivTpATUgHcfynUMRwdAA0IY7KlJ3T8twC/qiQH?=
 =?us-ascii?Q?UO/2B8UCTpZ0+UnRKf1qRZilFA+sfmwgMuBxxjKH7Qd/f5W+pVUcFLS1p9Tw?=
 =?us-ascii?Q?mgW2GK3cj6rwzShYm812vqJDOGl3YHd6D7vJ4iwi9/I2fhAgzBL3cKgFI3on?=
 =?us-ascii?Q?BY7Ab4Uxz9TLNExv4Qelrcr/k6JMdSbaSjJ855M5hl+qoLUAv4bnCk7pkE4X?=
 =?us-ascii?Q?er9dp5jMqCzADzX0QBsgN2cnADMKnvIe/cXud6kkeH9dIcvrxfMI21w9iC4o?=
 =?us-ascii?Q?D+oV3QaOfbI3/P1wUdaC2bOaYJn8QIcAeNRPrWl3co5HuX7su4ctmYcN95d8?=
 =?us-ascii?Q?HrXXOto1DoXf0M470CF6Y3P46eJbvTzKF0YRJ347DJ4QLINgNHRjIFXgHoFf?=
 =?us-ascii?Q?VJJl3uIU+snOt8bnAean8rxh2tRS7tpXzyGveZwQZdg+31pngXszHe6FQjDs?=
 =?us-ascii?Q?YFJ1Co70gH6/r/DREyel4/KWdpJLLaloPghpKDZS5FmQW3EczEUDQjYMcmFq?=
 =?us-ascii?Q?h98mVMKuaqSj5Nd8V88jZny4i28ucWeMgGbwVtCnHEmGS6sYnw8sAdvQvtGM?=
 =?us-ascii?Q?DqiosZlBRauAFs6XY6tPh2nsTN+5DbqXKdY2lDVKxf1muPyN7kNwIoe8HwmW?=
 =?us-ascii?Q?BgeCsqdjeSZnmrrY4dQKcSLt9BEsV9BPxqsnFCNbenE4JN+CE1blbT4GI+aJ?=
 =?us-ascii?Q?t2FoslJYiT4YvGnTN35oWAGqXYxDlb6UhgRZMBzQqG6GnnRDl1a6/8NZsc19?=
 =?us-ascii?Q?EFfHG5aKCgSAMGkUK7eZypRjjKHF3YKNaHaEMUYvbq9DVOVPU0GwUd9c2SRG?=
 =?us-ascii?Q?drDdqM4K4iI87L79YqMdYXWXJ98EzAy6+cZbSuW6MtD5yGwBcxmJHN6mQOMF?=
 =?us-ascii?Q?gA=3D=3D?=
X-MS-Exchange-CrossTenant-Network-Message-Id: d3b7bce2-636b-419b-71ed-08db983bbeb7
X-MS-Exchange-CrossTenant-AuthSource: PH8PR11MB8107.namprd11.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 08 Aug 2023 18:17:37.4214
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 46c98d88-e344-4ed4-8496-4ed7712e255d
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: unZDo+IzhrliBsZz/tMKYOlgg7Ng/dS8eyczFzMPco+9vGlUEEh32FOdRPbivEA8RI8CNMxZmXhmlnMmCSxNcZhtT3qYZ2hFYhvvdda1+XU=
X-MS-Exchange-Transport-CrossTenantHeadersStamped: CY8PR11MB7363
X-OriginatorOrg: intel.com
X-Spam-Status: No, score=-4.4 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH,
        DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_MED,
        SPF_HELO_NONE,SPF_NONE,URIBL_BLOCKED autolearn=ham autolearn_force=no
        version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on
        lindbergh.monkeyblade.net
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

Dionna Amalie Glaze wrote:
> >
> > I do not see sysfs precluding a use case like that. If the kernel can
> > call out to userspace for TLS connection setup [1], then advanced user
> > can call out to a daemon for workload provenance setup. Recall that TDX
> > will round trip through the quoting enclave for these reports and,
> > without measuring, that seems to have the potential to dominate the
> > setup time vs the communication to ask a daemon to convey a report.
> >
> 
> It's rather hard to get new daemons approved for container
> distributions since they end up as resource hogs.
> I really don't think it's appropriate to delegate to a daemon to
> single-thread use of a kernel interface when the interface could
> provide functional semantics to begin with.

That's fair, it's also not without precedence for the kernel to await a
strong motivation of a use case before taking on a higher maintenance
burden. Unifying kernel interfaces is important for maintainability and
difficult / needs care. sysfs simplifies maintainability (but exports
complexity to userspace), keyring simplifies that (but there is a valid
argument that this is not a key), ioctl complicates that (it is not as
amenable to transport unification as the above options).