------- Comment From niklas.schne...@ibm.com 2020-05-20 11:37 EDT-------
And in the meantime this has also been added to
the public s390 repository on kernel.org which also
includes the later Reviewed-by from Pierre Morel.

PCI/IOV: Introduce pci_iov_sysfs_link() function

https://git.kernel.org/pub/scm/linux/kernel/git/s390/linux.git/commit/?h=features&id=a1ceea67f2e5b73cebd456e7fb463b3052bc6344

s390/pci: create links between PFs and VFs

https://git.kernel.org/pub/scm/linux/kernel/git/s390/linux.git/commit/?h=features&id=e5794cf1a270d813a5b9373a6876487d4d154195

I've also tested that the patches apply clean on
focal master-next + the patches from LP 1874056

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https://bugs.launchpad.net/bugs/1879704

Title:
  [UBUNTU 20.04] s390x/pci: implement linking between PF and VF for
  multifunction devices

Status in Ubuntu on IBM z Systems:
  Incomplete
Status in linux package in Ubuntu:
  Incomplete

Bug description:
  As with other architectures, we must be able on s390x to verify the
  following relationships between PFs and VFs for proper management
  (including by libvirt) of network interfaces:

  1. Determine if a device is a virtual function: for other architectures this 
is currently available in the file `physfn` which is a link to the parent PF's 
device.
  2. Determine virtual functions of a physical function: for other 
architectures this is currently available as `virtfn{index}` links under the PF 
device's directory.
  3. Determine the physical function of a virtual function: on x86 this is 
currently available in the file `physfn` which is a link to the parent PF

  More details for the already existing parameters mentioned above can
  be found here: https://www.kernel.org/doc/Documentation/ABI/testing
  /sysfs-bus-pci

  Moreover creating not just the sysfs but also the in-kernel link
  (struct pci_dev->physfn) also allows us to use the common code path
  for disabling/shutdown of PFs.
  This code path is currently fenced off by the
  struct pci_dev->no_vf_scan flag of which s390 is currently the only user.

  This in turn allows for a graceful and orderly shutdown of VFs
  associated with a VF as triggered by:

  echo 0 > /sys/bus/pci/devices/<some_pf>/sriov_numvfs

  Previously this could leave the card in an unresponsive error state.

  The patches for this have been discussed and Acked-by the
  responsible upstream maintainer here:

  [RFC 0/2] Enable PF-VF linking with pdev->no_vf_scan (s390)
  
https://lore.kernel.org/linux-pci/20200506154139.90609-1-schne...@linux.ibm.com/

  [RFC 1/2] PCI/IOV: Introduce pci_iov_sysfs_link() function
  
https://lore.kernel.org/linux-pci/20200506154139.90609-2-schne...@linux.ibm.com/

  [RFC 2/2] s390/pci: create links between PFs and VFs
  
https://lore.kernel.org/linux-pci/20200506154139.90609-2-schne...@linux.ibm.com/

  They are currently queued to be posted to the public s390 Kernel
  repository and linux-next / 5.8.
  These depend on the previous multi-function/enumeration rework.

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