Re: [PATCH] PCI: rcar-host: Use proper IRQ domain

[Nam Cao <namcao@linutronix.de>]

Claudiu <claudiu.beznea@tuxon.dev> writes:
> From: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
>
> Starting with commit dd26c1a23fd5 ("PCI: rcar-host: Switch to
> msi_create_parent_irq_domain()"), the MSI parent IRQ domain is NULL because
> the object of type struct irq_domain_info passed to:
>
> msi_create_parent_irq_domain() ->
>   irq_domain_instantiate()() ->
>     __irq_domain_instantiate()
>
> has no reference to the parent IRQ domain. Using msi->domain->parent as an
> argument for generic_handle_domain_irq() leads to a "Unable to handle
> kernel NULL pointer dereference at virtual address" error.

Right. Before that commit, msi->domain is the domain of the children PCI
devices, and msi->domain->parent is the domain of this device.

That commit changed msi->domain to be the domain of this
device. msi->domain->parent does not exist anymore.

drivers/pci/controller/pcie-xilinx.c has the same issue, let me send a
patch..

> This error was identified while switching the upcoming RZ/G3S PCIe host
> controller driver to msi_create_parent_irq_domain() (which was using a
> similar pattern to handle MSIs (see link section)), but it was not tested
> on hardware using the pcie-rcar-host controller driver due to lack of
> hardware.
>
> Link: https://lore.kernel.org/all/20250704161410.3931884-6-claudiu.beznea.uj@bp.renesas.com/
> Fixes: dd26c1a23fd5 ("PCI: rcar-host: Switch to msi_create_parent_irq_domain()")
> Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>

Reviewed-by: Nam Cao <namcao@linutronix.de>