[PATCH v6 0/5] PCI: Rework pci_scan_slot() and isolated PCI functions

[Niklas Schnelle <schnelle@linux.ibm.com>]

Hi Bjorn,

In an earlier version[0], I sought to apply the existing jailhouse special case
for isolated PCI functions to s390. As Bjorn noted in[1] there appears to be
some potential for cleaning things up and removing duplication.

This series attempts to do this cleanup (Patches 1 through 3) followed by enabling
isolated PCI functions for s390 (Patches 4 and 5).

Testing:
- On s390 with SR-IOV and a ConnectX NIC with PF 1 but not PF 0 passed throug
  i.e. the isolated function case. Also of course with just VFs and an NVMe.
- On x86_64 on a desktop system where ARI is disabled and with an SR-IOV NIC
  with non-contiguous VFs as well as the usual other PCI devices.

Thanks,
Niklas

[0] https://lore.kernel.org/linux-pci/20220404095346.2324666-1-schnelle@linux.ibm.com/
[1] https://lore.kernel.org/linux-pci/20220408224514.GA353445@bhelgaas/

Changes v5 -> v6:
- Added a patch (2) which separates the ARI case into its own function
- Some whitespace changes to remove unnecesssary empty lines
Changes v4 -> v5:
- Remove unintended whitespace change in patch 1
Changes v3 -> v4:
- Use a do {} while loop in pci_scan_slot() as it is simpler (Bjorn)
- Explicitly check "fn == 0" as it is not a pointer or bool (Bjorn)
- Keep the "!dev" check in the ARI branch of next_fn() (Bjorn)
- Moved the "fn == 0 && !dev" condition out of next_fn() into pci_scan_slot().
  This allows us to keep the "!dev" case in the ARI branch and means there are
  no new conditions in next_fn() making it easier to verify that its behavior
  is equivalent to the existing code.
- Guard the assignment of dev->multifunction with "fn > 0"
  instead of "nr > 0". This matches the existing logic more closely and works
  for the jailhouse case which unconditionally sets dev->multifunction for
  "fn > 0". This also means fn == 0 is the single "first iteration" test.
- Remove some unneeded whitespace in patch 2

Changes v2 -> v3:
- Removed now unused nr_devs variable (kernel test robot)

Niklas Schnelle (5):
  PCI: Clean up pci_scan_slot()
  PCI: Split out next_ari_fn() from next_fn()
  PCI: Move jailhouse's isolated function handling to pci_scan_slot()
  PCI: Extend isolated function probing to s390
  s390/pci: allow zPCI zbus without a function zero

 arch/s390/pci/pci_bus.c    | 82 +++++++++---------------------------
 drivers/pci/probe.c        | 86 ++++++++++++++++++--------------------
 include/linux/hypervisor.h |  8 ++++
 3 files changed, 68 insertions(+), 108 deletions(-)

-- 
2.32.0