On Tue, Jan 24, 2023 at 05:51:55PM -0600, Bjorn Helgaas wrote: > On Tue, Jan 24, 2023 at 12:43:15PM +0000, Jonathan Cameron wrote: > > On Mon, 23 Jan 2023 11:20:00 +0100 Lukas Wunner <lukas@xxxxxxxxx> wrote: > > > An upcoming user of DOE is CMA (Component Measurement and Authentication, > > > PCIe r6.0 sec 6.31). > > > > > > It builds on SPDM (Security Protocol and Data Model): > > > https://www.dmtf.org/dsp/DSP0274 > > > > > > SPDM message sizes are not always a multiple of dwords. To transport > > > them over DOE without using bounce buffers, allow sending requests and > > > receiving responses whose final dword is only partially populated. [...] > > IIRC, at the time feedback was strongly in favour of making > > the handling of non dword payloads a problem for the caller (e.g. PCI/CMA) > > not the DOE core, mainly so that we could keep the layering simple. > > DOE part of PCI spec says DWORD multiples only, CMA has non dword > > entries. > > I can't remember, but I might have been the voice in favor of making > it the caller's problem. Your argument about dealing with it here > makes a lot of sense, and I'm OK with it, but I *would* like to add > some text to the commit log and comments in the code about what is > happening here. Otherwise there's an unexplained disconnect between > the DWORD spec language and the byte-oriented code. In v3 I amended both the commit message and the kerneldoc for pci_doe() to make it clear that support for arbitrary-sized request and response buffers is not stipulated by the spec, but merely for the convenience of the caller. Thanks, Lukas
