PCI/MSI: Fix MSI IRQ domains for VFs on virtual buses

SR-IOV creates a virtual bus where bus->self is NULL.  When we add VFs and
scan for an MSI domain, pci_set_bus_msi_domain() dereferences bus->self,
which causes a kernel NULL pointer dereference oops.

Scan up to the parent bus until we find a real bridge where we can get the
MSI domain.

[bhelgaas: changelog]
Fixes: 44aa0c657e3e ("PCI/MSI: Add hooks to populate the msi_domain field")
Tested-by: Joerg Roedel <joro@8bytes.org>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Bjorn Helgaas <helgaas@kernel.org>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>

1 files changed, 11 insertions, 6 deletions

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index c8cc0e62a7b9..8361d27e5eca 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -676,15 +676,20 @@ static struct irq_domain *pci_host_bridge_msi_domain(struct pci_bus *bus)
 static void pci_set_bus_msi_domain(struct pci_bus *bus)
 {
         struct irq_domain *d;
+        struct pci_bus *b;
 
         /*
-         * Either bus is the root, and we must obtain it from the
-         * firmware, or we inherit it from the bridge device.
+         * The bus can be a root bus, a subordinate bus, or a virtual bus
+         * created by an SR-IOV device.  Walk up to the first bridge device
+         * found or derive the domain from the host bridge.
          */
-        if (pci_is_root_bus(bus))
-                d = pci_host_bridge_msi_domain(bus);
-        else
-                d = dev_get_msi_domain(&bus->self->dev);
+        for (b = bus, d = NULL; !d && !pci_is_root_bus(b); b = b->parent) {
+                if (b->self)
+                        d = dev_get_msi_domain(&b->self->dev);
+        }
+
+        if (!d)
+                d = pci_host_bridge_msi_domain(b);
 
         dev_set_msi_domain(&bus->dev, d);
 }