[PULL 02/31] vfio/igd: Enable quirks when IGD is not the primary display

["Cédric Le Goater" <clg@redhat.com>]

From: Tomita Moeko <tomitamoeko@gmail.com>

Since linux 6.15, commit 41112160ca87 ("vfio/pci: match IGD devices in
display controller class"), IGD related regions are also exposed when
IGD is not primary display (device class is Display controller).

Allow IGD quirks to be enabled in this configuration so that guests can
have display output on IGD when it is not the primary display.

Signed-off-by: Tomita Moeko <tomitamoeko@gmail.com>
Reviewed-by: Alex Williamson <alex.williamson@redhat.com>
Link: https://lore.kernel.org/qemu-devel/20250813160510.23553-1-tomitamoeko@gmail.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>
---
 hw/vfio/pci.h | 5 +++++
 hw/vfio/igd.c | 7 ++++---
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/hw/vfio/pci.h b/hw/vfio/pci.h
index 810a842f4a153d4bcc924a6984c6dae58e1e69dd..923cf9c2f79d078546239bf67195d6ba8157265a 100644
--- a/hw/vfio/pci.h
+++ b/hw/vfio/pci.h
@@ -203,6 +203,11 @@ static inline bool vfio_is_vga(VFIOPCIDevice *vdev)
     return (vdev->class_code >> 8) == PCI_CLASS_DISPLAY_VGA;
 }
 
+static inline bool vfio_is_base_display(VFIOPCIDevice *vdev)
+{
+    return (vdev->class_code >> 16) == PCI_BASE_CLASS_DISPLAY;
+}
+
 /* MSI/MSI-X/INTx */
 void vfio_pci_vector_init(VFIOPCIDevice *vdev, int nr);
 void vfio_pci_add_kvm_msi_virq(VFIOPCIDevice *vdev, VFIOMSIVector *vector,
diff --git a/hw/vfio/igd.c b/hw/vfio/igd.c
index ee0767b0b89c085a5147369dd6fcbd3ff21f8927..f116c40ccd933c8e6e7fd99d599c6372c26973e1 100644
--- a/hw/vfio/igd.c
+++ b/hw/vfio/igd.c
@@ -460,7 +460,7 @@ void vfio_probe_igd_bar0_quirk(VFIOPCIDevice *vdev, int nr)
     int gen;
 
     if (!vfio_pci_is(vdev, PCI_VENDOR_ID_INTEL, PCI_ANY_ID) ||
-        !vfio_is_vga(vdev) || nr != 0) {
+        !vfio_is_base_display(vdev) || nr != 0) {
         return;
     }
 
@@ -518,7 +518,7 @@ static bool vfio_pci_igd_config_quirk(VFIOPCIDevice *vdev, Error **errp)
     Error *err = NULL;
 
     if (!vfio_pci_is(vdev, PCI_VENDOR_ID_INTEL, PCI_ANY_ID) ||
-        !vfio_is_vga(vdev)) {
+        !vfio_is_base_display(vdev)) {
         return true;
     }
 
@@ -534,12 +534,13 @@ static bool vfio_pci_igd_config_quirk(VFIOPCIDevice *vdev, Error **errp)
     /*
      * For backward compatibility, enable legacy mode when
      * - Device geneation is 6 to 9 (including both)
-     * - IGD claims VGA cycles on host
+     * - IGD exposes itself as VGA controller and claims VGA cycles on host
      * - Machine type is i440fx (pc_piix)
      * - IGD device is at guest BDF 00:02.0
      * - Not manually disabled by x-igd-legacy-mode=off
      */
     if ((vdev->igd_legacy_mode != ON_OFF_AUTO_OFF) &&
+        vfio_is_vga(vdev) &&
         (gen >= 6 && gen <= 9) &&
         !(gmch & IGD_GMCH_VGA_DISABLE) &&
         !strcmp(MACHINE_GET_CLASS(qdev_get_machine())->family, "pc_piix") &&
-- 
2.51.0