iommu/vt-d: Cure VF irqdomain hickup

[Thomas Gleixner]

The recent changes to store the MSI irqdomain pointer in struct device
missed that Intel DMAR does not register virtual function devices.  Due to
that a VF device gets the plain PCI-MSI domain assigned and then issues
compat MSI messages which get caught by the interrupt remapping unit.

Cure that by inheriting the irq domain from the physical function
device.

That's a temporary workaround. The correct fix is to inherit the irq domain
from the bus, but that's a larger effort which needs quite some other
changes to the way how x86 manages PCI and MSI domains.

Fixes: 85a8dfc57a0b ("iommm/vt-d: Store irq domain in struct device")
Reported-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
---
 drivers/iommu/intel/dmar.c |   19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

--- a/drivers/iommu/intel/dmar.c
+++ b/drivers/iommu/intel/dmar.c
@@ -333,6 +333,11 @@ static void  dmar_pci_bus_del_dev(struct
 	dmar_iommu_notify_scope_dev(info);
 }
 
+static inline void vf_inherit_msi_domain(struct pci_dev *pdev)
+{
+	dev_set_msi_domain(&pdev->dev, dev_get_msi_domain(&pdev->physfn->dev));
+}
+
 static int dmar_pci_bus_notifier(struct notifier_block *nb,
 				 unsigned long action, void *data)
 {
@@ -342,8 +347,20 @@ static int dmar_pci_bus_notifier(struct
 	/* Only care about add/remove events for physical functions.
 	 * For VFs we actually do the lookup based on the corresponding
 	 * PF in device_to_iommu() anyway. */
-	if (pdev->is_virtfn)
+	if (pdev->is_virtfn) {
+		/*
+		 * Note: This is a horrible hack and needs to be cleaned
+		 * up by assigning the domain to the bus, but that's too
+		 * big of a change for post rc3.
+		 *
+		 * Ensure that the VF device inherits the irq domain of the
+		 * PF device:
+		 */
+		if (action == BUS_NOTIFY_ADD_DEVICE)
+			vf_inherit_msi_domain(pdev);
 		return NOTIFY_DONE;
+	}
+
 	if (action != BUS_NOTIFY_ADD_DEVICE &&
 	    action != BUS_NOTIFY_REMOVED_DEVICE)
 		return NOTIFY_DONE;