vfio/pci: match IGD devices in display controller class

IGD device can either expose as a VGA controller or display controller
depending on whether it is configured as the primary display device in
BIOS. In both cases, the OpRegion may be present. A new helper function
vfio_pci_is_intel_display() is introduced to check if the device might
be an IGD device.

Signed-off-by: Tomita Moeko <tomitamoeko@gmail.com>
Link: https://lore.kernel.org/r/20250123163416.7653-1-tomitamoeko@gmail.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

Author: tomitamoeko

drivers/vfio/pci/vfio_pci.c

@@ -111,9 +111,7 @@ static int vfio_pci_open_device(struct vfio_device *core_vdev)
 	if (ret)
 		return ret;
 
-	if (vfio_pci_is_vga(pdev) &&
-	    pdev->vendor == PCI_VENDOR_ID_INTEL &&
-	    IS_ENABLED(CONFIG_VFIO_PCI_IGD)) {
+	if (vfio_pci_is_intel_display(pdev)) {
 		ret = vfio_pci_igd_init(vdev);
 		if (ret && ret != -ENODEV) {
 			pci_warn(pdev, "Failed to setup Intel IGD regions\n");

drivers/vfio/pci/vfio_pci_igd.c

@@ -435,6 +435,12 @@ static int vfio_pci_igd_cfg_init(struct vfio_pci_core_device *vdev)
 	return 0;
 }
 
+bool vfio_pci_is_intel_display(struct pci_dev *pdev)
+{
+	return (pdev->vendor == PCI_VENDOR_ID_INTEL) &&
+	       ((pdev->class >> 16) == PCI_BASE_CLASS_DISPLAY);
+}
+
 int vfio_pci_igd_init(struct vfio_pci_core_device *vdev)
 {
 	int ret;

drivers/vfio/pci/vfio_pci_priv.h

@@ -67,8 +67,14 @@ void vfio_pci_memory_unlock_and_restore(struct vfio_pci_core_device *vdev,
 					u16 cmd);
 
 #ifdef CONFIG_VFIO_PCI_IGD
+bool vfio_pci_is_intel_display(struct pci_dev *pdev);
 int vfio_pci_igd_init(struct vfio_pci_core_device *vdev);
 #else
+static inline bool vfio_pci_is_intel_display(struct pci_dev *pdev)
+{
+	return false;
+}
+
 static inline int vfio_pci_igd_init(struct vfio_pci_core_device *vdev)
 {
 	return -ENODEV;