PCI: vmd: Assign VMD IRQ domain before enumeration

During the boot process all the PCI devices are assigned default PCI-MSI
IRQ domain including VMD endpoint devices. If interrupt-remapping is
enabled by IOMMU, the PCI devices except VMD get new INTEL-IR-MSI IRQ
domain. And VMD is supposed to create and assign a separate VMD-MSI IRQ
domain for its child devices in order to support MSI-X remapping
capabilities.

Now when MSI-X remapping in VMD is disabled in order to improve
performance, VMD skips VMD-MSI IRQ domain assignment process to its
child devices. Thus the devices behind VMD get default PCI-MSI IRQ
domain instead of INTEL-IR-MSI IRQ domain when VMD creates root bus and
configures child devices.

As a result host OS fails to boot and DMAR errors were observed when
interrupt remapping was enabled on Intel Icelake CPUs. For instance:

  DMAR: DRHD: handling fault status reg 2
  DMAR: [INTR-REMAP] Request device [0xe2:0x00.0] fault index 0xa00 [fault reason 0x25] Blocked a compatibility format interrupt request

To fix this issue, dev_msi_info struct in dev struct maintains correct
value of IRQ domain. VMD will use this information to assign proper IRQ
domain to its child devices when it doesn't create a separate IRQ domain.

Link: https://lore.kernel.org/r/20220511095707.25403-2-nirmal.patel@linux.intel.com
Signed-off-by: Nirmal Patel <nirmal.patel@linux.intel.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>

drivers/pci/controller/vmd.c

@@ -853,6 +853,9 @@ static int vmd_enable_domain(struct vmd_dev *vmd, unsigned long features)
 	vmd_attach_resources(vmd);
 	if (vmd->irq_domain)
 		dev_set_msi_domain(&vmd->bus->dev, vmd->irq_domain);
+	else
+		dev_set_msi_domain(&vmd->bus->dev,
+				   dev_get_msi_domain(&vmd->dev->dev));
 
 	vmd_acpi_begin();