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Thu, 22 Oct 2026 11:24:58 +0000 (GMT) Received: from li-43857255-d5e6-4659-90f1-fc5cee4750ad.ibm.com (unknown [9.61.112.79]) by smtpav05.dal12v.mail.ibm.com (Postfix) with ESMTP; Thu, 22 Oct 2026 11:24:58 +0000 (GMT) Message-ID: <2342b42699292d4e5fc85e5dd4d351a3f29ae336.camel@linux.ibm.com> Subject: Re: [PATCH RFC 00/20] attestation: Add a common subsystem and TDX support From: Mimi Zohar To: Jiri Pirko Cc: Jason Gunthorpe , Dionna Glaze , Jarkko Sakkinen , linux-coco@lists.linux.dev, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, x86@kernel.org, kvm@vger.kernel.org, linux-doc@vger.kernel.org, david.quigley@intel.com, lukas@wunner.de, ksinyuk@kernel.org, rodrigo.vivi@intel.com, cedric.xing@intel.com, sameo@meta.com, James.Bottomley@hansenpartnership.com, aik@amd.com, jpiotrowski@nvidia.com, qinkun@google.com, pgonda@google.com, jic23@kernel.org, alistair.francis@wdc.com, ankita@nvidia.com, suzuki.poulose@arm.com, kas@kernel.org, rick.p.edgecombe@intel.com, elena.reshetova@intel.com, dave.hansen@linux.intel.com, sathyanarayanan.kuppuswamy@linux.intel.com, peter.fang@intel.com, roberto.sassu@huawei.com In-Reply-To: References: <20261017231007.GP13920@nvidia.com> <20261019225658.GS13920@nvidia.com> <103486a4a29ecc7b72940dd051c00ae59266bd05.camel@linux.ibm.com> <20261021143529.GP3008132@nvidia.com> <8d8833fac61558a94af415143530884349584a2f.camel@linux.ibm.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Date: Thu, 22 Oct 2026 07:24:57 -0400 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Evolution 3.58.3 (3.58.3-2.fc43) X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYxMDIyMDA0NCBTYWx0ZWRfXxwiqvDMronE4 FQK3t3Ka+UBmU9zzP6ecQ8euUkLzhX4FWUA5V6YeEa4nH5caVDHgElYPouOKaWY3eO8sxSm1dQq H9/MmeIBwxmSOkAbNRJNbqEIv2r1PEY9b1MnCLPNEX55kJslBV5xEVWyyOyg9O0b9gQeRA+uSgu CHr64hZ9+eFCMu4Eg31bmjUZAedOL5lT0MHSsG3X9uxk9kuBE0aN07NN90hsjqZGukFlvNi+kbN qv0hKlFArX4L+q+8xOiOrZfCGEnyMBxfUuw+usWF8t2Xgp5pDm5omURfcg6/QKbMdBXe7lF7m35 0m9fwfHY2VP0GfW6qd8iWkBOJ3LOOtvHhZ5+qfxq7bKjK7mEf3MJAAs87PHyTjNgR1mM/wIovh7 9hTns2c/rsKR85/hvetAL40zf8fx8w== X-Proofpoint-ORIG-GUID: -IIoPKCgjZ0iA8b4LLnSoxnm_Zenbl1V X-Proofpoint-Spam-Info: AW1haW4tMjYxMDIyMDA0NCBTYWx0ZWRfX7uaAEEsIiURA ne+UmovPSY99pNXg6qSZquGDhuWRRe4QPG5ipgQoLtIN4s8DvmHYGAUjbPLNQTDpe8oGqQEQCGh DzJvSX212klGw9ZeBsDgcoe8AzXgIYU= X-Proofpoint-GUID: Dmhzh_FOqH-X5ktGgnB0OO9LGedtpqZL X-Authority-Analysis: v=2.4 cv=ZfSIpcVA c=1 sm=1 tr=0 ts=6ad9f28e cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=IkcTkHD0fZMA:10 a=660iZSQnnn4A:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=RzCfie-kr_QcCd8fBx8p:22 a=VnNF1IyMAAAA:8 a=cpN7-hlQ1AlEGHSOM8EA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.138,FMLib:17.12.100.49 definitions=2026-10-22_04,2026-10-21_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 spamscore=0 suspectscore=0 phishscore=0 bulkscore=0 lowpriorityscore=0 adultscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2610190000 definitions=main-2610220044 On Thu, 2026-10-22 at 12:54 +0200, Jiri Pirko wrote: > Wed, Oct 21, 2026 at 09:05:09PM +0200, zohar@linux.ibm.com wrote: > > On Wed, 2026-10-21 at 11:35 -0300, Jason Gunthorpe wrote: > > > On Wed, Oct 21, 2026 at 10:12:34AM -0400, Mimi Zohar wrote: > > > > > > I think for now we should not include a new dynamic log here, t= he uAPI > > > > > > around this Jiri drafted can remain a future step. I don't want= to > > > > > > open complicated discussions about new functionality at this > > > > > > stage. The whole CTLV idea in general is a big enough thing to = bite > > > > > > off for this series. > > > > >=20 > > > > > Okay, dropping the log from this set. > > > >=20 > > > > Thank you. Please keep in mind going forward, that the scarce hard= ware register > > > > limitation (like the 4 TDX RTMRs) should be resolved (e.g. by multi= plexing the > > > > extension path), not by combining distinct measurement lists. > > >=20 > > > I'm not sure what you mean? > > >=20 > > > Since the HW doesn't support sealing the only *technical* requirement > > > is the verifier can reproduce the measurement register hash. So long > > > as we can get there we can do whatever. > > >=20 > > > Multiplexing extension alone isn't enough. We need some scheme to > > > reconstruct interleaved logs too. > > >=20 > > > For example we could add an atomic sequence number for each > > > extend. Every log sharing a register can report the sequence > > > number. The verifier would have to globally sort all logs to confirm > > > the hash. > > >=20 > > > Hopefully we don't have to tackle this problem. I hope that 4 > > > registers is enough for Linux. One for IMA, one for systemd, one for > > > user? Plus a spare! > >=20 > > Agreed, I hope you don't have to tackle it either. > >=20 > > >=20 > > > Maybe we can build a multiplexed scheme on the spare? I don't know. > >=20 > > To avoid interleaving the logs, AI had suggested multiplexing or virtua= lization > > of the RTMRs. Whether is has any merit, I'll leave to you. Here's the= very > > short AI explanation: > >=20 > > "Instead of allowing external drivers or subsystems to execute a direct= , raw > > extend command to a specific hardware register index, the new attestati= on > > subsystem should act as a Hypervisor for Registers." >=20 > Isn't the hypervisor what we are doing now? I mean multiple extension > originators share the same register and eventually the same log. Or do > you suggest to go even further having a "generic_registerX" exposed for > every hw implementation allowing the user to have full abstraction? > The "generic_registerX" would be always alias to something hw specific, > like RTMR2 for example of TDX. I definitely prefer the latter, as everything continues to work as is with minimal, if any, change. AI's wording: =E2=80=A2 The Virtual Mapping: The [attestation] subsystem exposes "Virtual= RTMRs" (vRTMRs) internally to the kernel. =E2=80=A2 IMA's Dedicated Lane: The kernel config routes IMA to vRTMR_IMA. Mimi