On Thu, Aug 19, 2021 at 03:17:58PM +0100, Lorenzo Pieralisi wrote:

On Tue, Jul 27, 2021 at 02:06:49AM +0800, Boqun Feng wrote:

quoted

Hi,

This is the v6 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/ (local)
v2:	https://lore.kernel.org/lkml/20210503144635.2297386-1-boqun.feng@gmail.com/ (local)
v3:	https://lore.kernel.org/lkml/20210609163211.3467449-1-boqun.feng@gmail.com/ (local)
v4:	https://lore.kernel.org/lkml/20210714102737.198432-1-boqun.feng@gmail.com/ (local)
v5:	https://lore.kernel.org/lkml/20210720134429.511541-1-boqun.feng@gmail.com/ (local)

Changes since last version:

*	Rebase to 5.14-rc3

*	Comment fixes as suggested by Bjorn.

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 (7):
  PCI: Introduce domain_nr in pci_host_bridge
  PCI: Support populating MSI domains of root buses via bridges
  arm64: PCI: Restructure pcibios_root_bridge_prepare()
  arm64: PCI: Support root bridge preparation for Hyper-V
  PCI: hv: Set ->domain_nr of pci_host_bridge at probing time
  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             | 29 +++++++---
 drivers/pci/controller/pci-hyperv.c | 86 +++++++++++++++++------------
 drivers/pci/probe.c                 | 12 +++-
 include/linux/pci.h                 | 11 ++++
 4 files changed, 93 insertions(+), 45 deletions(-)

If we take this series via the PCI tree we'd need Catalin/Will ACKs on
patches 3-4.

Got it.

I need some time to look into [1] (thanks for that).

Without [1] patch 8 is ugly, that's no news. The question is whether
it is worth waiting for a kernel cycle to integrate [1] into this series
or not.

Is it really a problem if we postpone this series for another kernel
cycle so that we can look into it ?

Well, it's definitely better for me that we can have it in 5.15-rc1 ;-),
because it's a dependency for Hyper-V virtual PCI support on ARM64 and
we plan to send the rest of work in 5.15 cycle. And I can just base on
hyperv-next for the rest of the work if this is in 5.15-rc1. But yes,
it's not really a problem, since this one still needs to work with other
patches to support virtual PCI on ARM64 Hyper-V.

In fact, I personally don't think [1] is better than patch 8 (plus patch
3 & 4): playing with ->private seems dangerous and not very helpful on
readiblity, but I agree that we should explore every potential solution,
and that's why I send [1].

Regards,
Boqun

[1] https://lore.kernel.org/lkml/20210811153619.88922-1-boqun.feng@gmail.com/ (local)