Re: [PATCH v6 0/8] PCI: hv: Support host bridge probing on ARM64

[Lorenzo Pieralisi]

On Tue, Jul 27, 2021 at 02:06:49AM +0800, Boqun Feng wrote:
> 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@xxxxxxxxx/
> v2:	https://lore.kernel.org/lkml/20210503144635.2297386-1-boqun.feng@xxxxxxxxx/
> v3:	https://lore.kernel.org/lkml/20210609163211.3467449-1-boqun.feng@xxxxxxxxx/
> v4:	https://lore.kernel.org/lkml/20210714102737.198432-1-boqun.feng@xxxxxxxxx/
> v5:	https://lore.kernel.org/lkml/20210720134429.511541-1-boqun.feng@xxxxxxxxx/
> 
> 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.

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 ?

[1] https://lore.kernel.org/lkml/20210811153619.88922-1-boqun.feng@xxxxxxxxx/