[PATCH v4 4/4] virtio-gpu: advertise VIRTIO_GPU_F_BLOB_ALIGNMENT

[Lucas Amaral <lucaaamaral@gmail.com>]

Set blob_alignment to the host page size so the guest kernel can
align blob BAR offsets accordingly, avoiding alignment mismatches
with the VMM's memory mapping API (e.g., hv_vm_map on macOS).

Guest-side kernel support (drm_mm alignment) is pending upstream
Linux merge.

Signed-off-by: Lucas Amaral <lucaaamaral@gmail.com>
---
 hw/display/virtio-gpu.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/hw/display/virtio-gpu.c b/hw/display/virtio-gpu.c
index de7a86a7..44ae5034 100644
--- a/hw/display/virtio-gpu.c
+++ b/hw/display/virtio-gpu.c
@@ -1532,6 +1532,14 @@ void virtio_gpu_device_realize(DeviceState *qdev, Error **errp)
 #endif
     }
 
+    /*
+     * TODO: guest-side F_BLOB_ALIGNMENT support pending upstream Linux merge
+     * (Sergio Lopez's patches, Nov 2025). Until merged, the guest won't
+     * negotiate this feature. The host advertises it per OASIS virtio spec.
+     */
+    g->parent_obj.virtio_config.blob_alignment =
+        cpu_to_le32(qemu_real_host_page_size());
+
     if (!virtio_gpu_base_device_realize(qdev,
                                         virtio_gpu_handle_ctrl_cb,
                                         virtio_gpu_handle_cursor_cb,
-- 
2.52.0