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Wed, 30 Sep 2026 07:47:27 -0700 (PDT) Date: Wed, 30 Sep 2026 16:47:21 +0200 From: Jiri Pirko To: "Quigley, David" Cc: linux-coco@lists.linux.dev, linux-pci@vger.kernel.org, driver-core@lists.linux.dev Subject: Re: [PATCH 00/15] Device Evidence and Trust for PCI Security Protocol (TDISP) Message-ID: References: <20260805005533.GB28508@ziepe.ca> <2e721509-0aee-47ee-b17a-688876e02f74@amd.com> <20260902150125.GD2890729@ziepe.ca> Precedence: bulk X-Mailing-List: linux-pci@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Wed, Sep 30, 2026 at 04:14:00PM +0200, david.quigley@intel.com wrote: >Is there a way for this to be posted as its own patch set so we can provide >feedback inline? Also do we have any other potential uses for your proposed >ctlv mechanism or is attestation the only user at the moment? Will do that, still need to do some work on it before though. So far I focus on attestation with ctlv, as that is my immediate target. But the mechanism is quite generic, easy to be used by anyone. > >On 9/30/2026 5:22 AM, Jiri Pirko wrote: >> Fri, Sep 04, 2026 at 11:52:12AM +0200, jiri@resnulli.us wrote: >> > Thu, Sep 03, 2026 at 03:36:54PM +0200, lukas@wunner.de wrote: >> > > [+cc Jonathan, start of thread is here: >> > > https://lore.kernel.org/all/20260902150125.GD2890729@ziepe.ca/ >> > > ] >> > > >> > > On Wed, Sep 02, 2026 at 12:01:25PM -0300, Jason Gunthorpe wrote: >> > >> > [..] >> > >> > >> > > > I've asked Jiri Pirko to work on >> > > > the PCI evidence uAPI based on his deep netlink experience >> > > netlink isn't well suited to transport large blobs because the nlattr >> > > len is u16. (The len of the enclosing nlmsg is u32, which is sufficient.) >> > > >> > > Previous approaches, including the one proposed by Dan in this series, >> > > work around the problem by splitting the blob into a sequence of nlattrs. >> > > I think we should instead extend the netlink protocol with 32-bit "jumbo" >> > > attributes. >> > > >> > > I suggest we reserve bit 13 of nla_type as NLA_F_JUMBO and use the >> > > the first 4 bytes after the struct nlattr header as length (if the >> > > jumbo flag is set). >> > > >> > > >> > > A second problem is that the size of a socket buffer's linear data >> > > is limited. Also, copying the blob into the nlmsg is a bit wasteful >> > > and we'd want zero copy instead. The solution I've come up with is >> > > to attach the pages backing the blob as fragments to the skb. >> > > It's very simple, overcomes the skb size limitation and allows for >> > > zero-copy: >> > > >> > > https://github.com/l1k/linux/commit/6e73bb999128 >> > > >> > > That commit is from January and the time I've been able to devote >> > > to this has since been limited as my employer prioritized various >> > > AER feature gaps and fixes. >> > > >> > > I worked on this for native PCI device authentication, which faces >> > > the same netlink blob issue as TSM-mediated authentication. >> > > Both should use the same uABI for evidence exposure. Additionally, >> > > native device authentication may be used by non-PCI buses such as >> > > ATA or SCSI. The uABI should work for those use cases as well. >> > Not sure if netlink as actually the best fit for this purpose, >> > for large blob transfers ioctl-based iface is probably much more >> > convenient. I'm working on a uapi framework that make the best of >> > netlink and takes it over to a fd-based ioctl. I call it CTLV, here's >> > a link to an early pre-RFC draft: >> > >> > https://github.com/jpirko/linux_mlxsw/commits/wip_ctlv_pre_rfc_draft1/ >> > >> [..] >> >> Following up on this, I have a very early draft of an attestation >> framework here: >> >> https://github.com/jpirko/linux_mlxsw/commits/wip_attestation_pre_rfc_draft1/ >> >> It introduces a provider-neutral, fd-based interface for evidence >> retrieval, userspace verdicts tied to exact device/evidence generations, >> measurement registers and their journal, events, and device-security >> state transitions. Large evidence is written directly to referenced >> buffers instead of being split across Netlink messages. >> >> For this series, the intent is to replace the device-evidence >> Generic Netlink UAPI and the draft PCI/TSM evidence-accept UAPI. >> It does not replace PCI/TSM connect/disconnect or lock/unlock, >> nor the underlying device-trust, SPDM/IDE/TDISP, MMIO, or >> DMA machinery. >> >> The branch currently contains the core, a simulation provider with >> tests, and a TDX provider demonstrating the provider boundary. >> The PCI/TSM provider is not implemented yet.