On Thu, Jun 10, 2021 at 1:06 PM Dan Williams <dan.j.williams@xxxxxxxxx> wrote: > > On Mon, May 24, 2021 at 6:41 AM Jonathan Cameron > <Jonathan.Cameron@xxxxxxxxxx> wrote: > > > > Introduced in a PCI ECN [1], DOE provides a config space based mailbox with > > standard protocol discovery. Each mailbox is accessed through a DOE > > Extended Capability. > > > > A device may have 1 or more DOE mailboxes, each of which is allowed to > > support any number of protocols (some DOE protocol specifications apply > > additional restrictions). A given protocol may be supported on more than > > one DOE mailbox on a given function. > > > > If a driver wishes to access any number of DOE instances / protocols it > > makes a single call to pci_doe_register_all() which will find available > > DOEs, create the required infrastructure and cache the protocols they > > support. pci_doe_find() can then retrieve a pointer to an appropriate DOE > > instance. > > > > A synchronous interface is provided in pci_doe_exchange_sync() to perform a > > single query / response exchange. > > > > Testing conducted against QEMU using: > > > > https://lore.kernel.org/qemu-devel/1619454964-10190-1-git-send-email-cbrowy@xxxxxxxxxxxxxxxx/ > > Nice. > > I was hoping that by now QEMU upstream would have given us some > indication that this useful work that has a chance of being merged. I > fear it's only us CXL practitioner's that care. Perhaps the PCI IDE > support will get them to move on at least the DOE patches? > > > > > [1] https://members.pcisig.com/wg/PCI-SIG/document/14143 > > Data Object Exchange (DOE) - Approved 12 March 2020 > > > > Signed-off-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx> > > The core logic of this looks good to me. The interfaces for other code > to make use of this I feel can lean heavier on existing mechanics. A > few points come to mind: > > - Does this need to support anything more than queue depth 1? I know > the specification seems to allow for some overlapping and queueing, > but I don't think there are any use cases that are precluded if the > max number of tasks in flight for a given DOE is one. > > - Once its queue depth 1 then the list of tasks can be replaced with a > wait_queue_head_t where submitters wait for the previous task to > finish. > > - This appears to be the prototypical scenario for deploying the new > auxiliary bus facility. Rather than custom code device-like facilities > (lists and parents etc) in 'struct pci_doe' just make pci_doe a device > directly (auxiliary-device) and separate the infrastructure that > drives that device to a driver (auxiliary-driver). That makes the > lifetime management more idiomatic, allows for user space to have > typical driver-binding controls to manage kernel-user DOE conflicts, > and it allows for typical driver services like devm. Hi Jonathan, Are you waiting on me to take a shot at refactoring the DOE driver into this proposed auxiliary device/driver organization? I am happy to do that if you've moved on to looking at the kernel-side SPDM implementation [1]. I would expect DOE, SPDM, and IDE would be a useful topic to discuss at the the Plumbers PCI Microconference assuming we do not solve all the open issues before September. [1]: https://lore.kernel.org/r/20210629132520.00000d1f@xxxxxxxxxx
