[RFC v4 0/7] PCI: hv: Support host bridge probing on ARM64

[Boqun Feng]

Hi Bjorn, Arnd and Marc,

This is the v4 for the preparation of virtual PCI support on Hyper-V
ARM64. Previous versions:

v1:	https://lore.kernel.org/lkml/20210319161956.2838291-1-boqun.feng@gmail.com/
v2:	https://lore.kernel.org/lkml/20210503144635.2297386-1-boqun.feng@gmail.com/
v3:	https://lore.kernel.org/lkml/20210609163211.3467449-1-boqun.feng@gmail.com/

Changes since last version:

*	Rebase to 5.14-rc1.

*	Change the ordering of patches, now the first three patches are
	non Hyper-V specific ones (i.e. patches touch general code),
	make it convenient to review.

The basic problem we need to resolve is that ARM64 is an arch with
PCI_DOMAINS_GENERIC=y, so the bus sysdata is pci_config_window. However,
Hyper-V PCI provides a paravirtualized PCI interface, so there is no
actual pci_config_window for a PCI host bridge, so no information can be
retrieve from the pci_config_window of a Hyper-V virtual PCI bus. Also
there is no corresponding ACPI device for the Hyper-V PCI root bridge,
which introduces a special case when trying to find the ACPI device from
the sysdata (see patch #3).

With this patchset, we could enable the virtual PCI on Hyper-V ARM64
guest with other code under development.

Comments and suggestions are welcome.

Regards,
Boqun

Arnd Bergmann (1):
  PCI: hv: Generify PCI probing

Boqun Feng (6):
  PCI: Introduce domain_nr in pci_host_bridge
  PCI: Allow msi domain set-up at host probing time
  arm64: PCI: Support root bridge preparation for Hyper-V PCI
  PCI: hv: Use pci_host_bridge::domain_nr for PCI domain
  PCI: hv: Set up msi domain at bridge probing time
  PCI: hv: Turn on the host bridge probing on ARM64

 arch/arm64/kernel/pci.c             |  8 ++-
 drivers/pci/controller/pci-hyperv.c | 86 +++++++++++++++++------------
 drivers/pci/probe.c                 | 11 +++-
 include/linux/pci.h                 | 10 ++++
 4 files changed, 76 insertions(+), 39 deletions(-)

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