On Fri, Mar 19, 2021 at 10:14 PM Bjorn Helgaas <helgaas@xxxxxxxxxx> wrote:
> > However, for a virtualized PCI bus, there might be no enough data in of
> > or acpi table to create a pci_config_window. This is similar to the case
> > where CONFIG_PCI_DOMAINS_GENERIC=n, IOW, architectures use their own
> > structure for sysdata, so no apci table lookup is required.
> >
> > In order to enable Hyper-V's virtual PCI (which doesn't have acpi table
> > entry for PCI) on ARM64 (which selects CONFIG_PCI_DOMAINS_GENERIC), we
> > introduce arch-specific pci sysdata (similar to the one for x86) for
> > ARM64, and allow the core PCI code to detect the type of sysdata at the
> > runtime. The latter is achieved by adding a pci_ops::use_arch_sysdata
> > field.
> >
> > Originally-by: Sunil Muthuswamy <sunilmut@xxxxxxxxxxxxx>
> > Signed-off-by: Boqun Feng (Microsoft) <boqun.feng@xxxxxxxxx>
> > ---
> > arch/arm64/include/asm/pci.h | 29 +++++++++++++++++++++++++++++
> > arch/arm64/kernel/pci.c | 15 ++++++++++++---
> > include/linux/pci.h | 3 +++
> > 3 files changed, 44 insertions(+), 3 deletions(-)
> >
> > diff --git a/arch/arm64/include/asm/pci.h b/arch/arm64/include/asm/pci.h
> > index b33ca260e3c9..dade061a0658 100644
> > --- a/arch/arm64/include/asm/pci.h
> > +++ b/arch/arm64/include/asm/pci.h
> > @@ -22,6 +22,16 @@
> >
> > extern int isa_dma_bridge_buggy;
> >
> > +struct pci_sysdata {
> > + int domain; /* PCI domain */
> > + int node; /* NUMA Node */
> > +#ifdef CONFIG_ACPI
> > + struct acpi_device *companion; /* ACPI companion device */
> > +#endif
> > +#ifdef CONFIG_PCI_MSI_IRQ_DOMAIN
> > + void *fwnode; /* IRQ domain for MSI assignment */
> > +#endif
> > +};
>
> Our PCI domain code is really a mess (mostly my fault) and I hate to
> make it even more complicated by adding more switches, e.g.,
> ->use_arch_sysdata.
>
> I think the design problem is that PCI host bridge drivers should
> supply the PCI domain up front instead of having callbacks to extract
> it.
>
> We could put "int domain_nr" in struct pci_host_bridge, and the arch
> code or host bridge driver (pcibios_init_hw(), *_pcie_probe(), VMD,
> HV, etc) could fill in pci_host_bridge.domain_nr before calling
> pci_scan_root_bus_bridge() or pci_host_probe().
>
> Then maybe we could get rid of pci_bus_find_domain_nr() and some of
> the needlessly arch-specific implementations of pci_domain_nr().
> I think we likely could get rid of CONFIG_PCI_DOMAINS_GENERIC, too,
> eventually.
Agreed. I actually still have a (not really tested) patch series to clean up
the pci host bridge registration, and this should make this a lot easier
to add on top.
I should dig that out of my backlog and post for review.
Arnd
