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.

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>
---
 drivers/pci/controller/pcie-rcar-host.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/pci/controller/pcie-rcar-host.c b/drivers/pci/controller/pcie-rcar-host.c
index fe288fd770c4..4780e0109e58 100644
--- a/drivers/pci/controller/pcie-rcar-host.c
+++ b/drivers/pci/controller/pcie-rcar-host.c
@@ -584,7 +584,7 @@ static irqreturn_t rcar_pcie_msi_irq(int irq, void *data)
 		unsigned int index = find_first_bit(&reg, 32);
 		int ret;
 
-		ret = generic_handle_domain_irq(msi->domain->parent, index);
+		ret = generic_handle_domain_irq(msi->domain, index);
 		if (ret) {
 			/* Unknown MSI, just clear it */
 			dev_dbg(dev, "unexpected MSI\n");
-- 
2.43.0

On Sat, 09 Aug 2025 17:44:47 +0300, Claudiu wrote:
> 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()
> 
> [...]

Applied, thanks!

[1/1] PCI: rcar-host: Use proper IRQ domain
      commit: d3fee10e40a938331e2aae34348691136db31304

Best regards,
-- 
Manivannan Sadhasivam <mani@kernel.org>

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>