[PULL 05/28] vfio/igd: Always emulate ASLS (OpRegion) register

["Cédric Le Goater" <clg@redhat.com>]

From: Tomita Moeko <tomitamoeko@gmail.com>

ASLS register represents the base address of OpRegion, and it is
programmed with HPA. In IGD passthrough scenario, it needs to be
reprogrammed with GPA by guest firmware. To prevent guest accessing
wrong memory range, ASLS should always be emulated and cleared.

In GVT-g scenario, emulating ASLS is unnecessary as access is handled
by kvmgt backend [1].

[1]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/gpu/drm/i915/gvt/cfg_space.c?h=v6.14#n295

Signed-off-by: Tomita Moeko <tomitamoeko@gmail.com>
Reviewed-by: Corvin Köhne <c.koehne@beckhoff.com>
Reviewed-by: Alex Williamson <alex.williamson@redhat.com>
Tested-by: Alex Williamson <alex.williamson@redhat.com>
Link: https://lore.kernel.org/qemu-devel/20250505170305.23622-3-tomitamoeko@gmail.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>
---
 hw/vfio/igd.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/hw/vfio/igd.c b/hw/vfio/igd.c
index e06484c9112f104b87c18bb7b2d0a2cd2de1992e..b1fce76f7250c2b2185cc259ac673d0d595832e8 100644
--- a/hw/vfio/igd.c
+++ b/hw/vfio/igd.c
@@ -182,10 +182,6 @@ static bool vfio_pci_igd_opregion_init(VFIOPCIDevice *vdev,
 
     trace_vfio_pci_igd_opregion_enabled(vdev->vbasedev.name);
 
-    pci_set_long(vdev->pdev.config + IGD_ASLS, 0);
-    pci_set_long(vdev->pdev.wmask + IGD_ASLS, ~0);
-    pci_set_long(vdev->emulated_config_bits + IGD_ASLS, ~0);
-
     return true;
 }
 
@@ -584,7 +580,15 @@ static bool vfio_pci_igd_config_quirk(VFIOPCIDevice *vdev, Error **errp)
     if ((vdev->features & VFIO_FEATURE_ENABLE_IGD_LPC) &&
         !vfio_pci_igd_setup_lpc_bridge(vdev, errp)) {
         goto error;
-     }
+    }
+
+    /*
+     * ASLS (OpRegion address) is read-only, emulated
+     * It contains HPA, guest firmware need to reprogram it with GPA.
+     */
+    pci_set_long(vdev->pdev.config + IGD_ASLS, 0);
+    pci_set_long(vdev->pdev.wmask + IGD_ASLS, ~0);
+    pci_set_long(vdev->emulated_config_bits + IGD_ASLS, ~0);
 
     /*
      * Allow user to override dsm size using x-igd-gms option, in multiples of
-- 
2.49.0