virtio-gpu: Support DRM native context

Add support for DRM native contexts to VirtIO-GPU. DRM context is enabled
using a new virtio-gpu-gl device option "drm_native_context=on".

Unlike Virgl and Venus contexts that operate on application API level,
DRM native contexts work on a kernel UAPI level. This lower level results
in a lightweight context implementations that yield better performance.

Reviewed-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Tested-by: Alex Bennée <alex.bennee@linaro.org>
Acked-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>
Reviewed-by: Yiwei Zhang <zzyiwei@gmail.com>
Tested-by: Yiwei Zhang <zzyiwei@gmail.com>
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Message-ID: <20260303151422.977399-11-dmitry.osipenko@collabora.com>
Message-ID: <20260304165043.1437519-13-alex.bennee@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>

docs/system/devices/virtio/virtio-gpu.rst

@@ -84,6 +84,17 @@ of virtio-gpu host memory window. This is typically between 256M and 8G.
 
 .. _venus: https://gitlab.freedesktop.org/virgl/venus-protocol/
 
+DRM native context is supported since release of `virglrenderer`_ v1.0.0
+using `drm`_ protocol.  ``DRM`` virtio-gpu capability set ("capset") requires
+host blob support (``hostmem`` and ``blob`` fields) and should be enabled
+using ``drm_native_context`` field.  The ``hostmem`` field specifies the size
+of virtio-gpu host memory window. This is typically between 256M and 8G.
+
+.. parsed-literal::
+    -device virtio-gpu-gl,hostmem=8G,blob=on,drm_native_context=on
+
+.. _drm: https://gitlab.freedesktop.org/virgl/virglrenderer/-/tree/main/src/drm
+
 virtio-gpu rutabaga
 -------------------
 

hw/display/virtio-gpu-gl.c

@@ -159,6 +159,8 @@ static const Property virtio_gpu_gl_properties[] = {
                     VIRTIO_GPU_FLAG_STATS_ENABLED, false),
     DEFINE_PROP_BIT("venus", VirtIOGPU, parent_obj.conf.flags,
                     VIRTIO_GPU_FLAG_VENUS_ENABLED, false),
+    DEFINE_PROP_BIT("drm_native_context", VirtIOGPU, parent_obj.conf.flags,
+                    VIRTIO_GPU_FLAG_DRM_ENABLED, false),
 };
 
 static void virtio_gpu_gl_device_unrealize(DeviceState *qdev)

hw/display/virtio-gpu-virgl.c

@@ -1323,6 +1323,25 @@ int virtio_gpu_virgl_init(VirtIOGPU *g)
     if (virtio_gpu_venus_enabled(g->parent_obj.conf)) {
         flags |= VIRGL_RENDERER_VENUS | VIRGL_RENDERER_RENDER_SERVER;
     }
+    if (virtio_gpu_drm_enabled(g->parent_obj.conf)) {
+        flags |= VIRGL_RENDERER_DRM;
+
+        if (!(flags & VIRGL_RENDERER_ASYNC_FENCE_CB)) {
+            /*
+             * Virglrenderer skips enabling DRM context support without
+             * enabled async-fence feature. VirtIO-GPU will initialize
+             * successfully, but DRM context won't be available in guest.
+             *
+             * For vrend async-fencing can be enabled only if EGL display
+             * is used. Vrend can't be disabled in QEMU, hence DRM implicitly
+             * requires EGL too.
+             *
+             * Async-fence was bugged in virglrenderer versions <= 1.1.1.
+             */
+            error_report("drm requires egl display and virglrenderer >= 1.2.0");
+            return -EINVAL;
+        }
+    }
 #endif
 
     ret = virgl_renderer_init(g, flags, &virtio_gpu_3d_cbs);
@@ -1386,5 +1405,14 @@ GArray *virtio_gpu_virgl_get_capsets(VirtIOGPU *g)
         }
     }
 
+    if (virtio_gpu_drm_enabled(g->parent_obj.conf)) {
+        virgl_renderer_get_cap_set(VIRTIO_GPU_CAPSET_DRM,
+                                   &capset_max_ver,
+                                   &capset_max_size);
+        if (capset_max_size) {
+            virtio_gpu_virgl_add_capset(capset_ids, VIRTIO_GPU_CAPSET_DRM);
+        }
+    }
+
     return capset_ids;
 }

hw/display/virtio-gpu.c

@@ -1517,6 +1517,21 @@ void virtio_gpu_device_realize(DeviceState *qdev, Error **errp)
 #endif
     }
 
+    if (virtio_gpu_drm_enabled(g->parent_obj.conf)) {
+#ifdef VIRGL_VERSION_MAJOR
+    #if VIRGL_VERSION_MAJOR >= 1
+        if (!virtio_gpu_blob_enabled(g->parent_obj.conf) ||
+            !virtio_gpu_hostmem_enabled(g->parent_obj.conf)) {
+            error_setg(errp, "drm requires enabled blob and hostmem options");
+            return;
+        }
+    #else
+        error_setg(errp, "old virglrenderer, drm unsupported");
+        return;
+    #endif
+#endif
+    }
+
     if (!virtio_gpu_base_device_realize(qdev,
                                         virtio_gpu_handle_ctrl_cb,
                                         virtio_gpu_handle_cursor_cb,

include/hw/virtio/virtio-gpu.h

@@ -100,6 +100,7 @@ enum virtio_gpu_base_conf_flags {
     VIRTIO_GPU_FLAG_RUTABAGA_ENABLED,
     VIRTIO_GPU_FLAG_VENUS_ENABLED,
     VIRTIO_GPU_FLAG_RESOURCE_UUID_ENABLED,
+    VIRTIO_GPU_FLAG_DRM_ENABLED,
 };
 
 #define virtio_gpu_virgl_enabled(_cfg) \
@@ -122,6 +123,8 @@ enum virtio_gpu_base_conf_flags {
     (_cfg.hostmem > 0)
 #define virtio_gpu_venus_enabled(_cfg) \
     (_cfg.flags & (1 << VIRTIO_GPU_FLAG_VENUS_ENABLED))
+#define virtio_gpu_drm_enabled(_cfg) \
+    (_cfg.flags & (1 << VIRTIO_GPU_FLAG_DRM_ENABLED))
 
 struct virtio_gpu_base_conf {
     uint32_t max_outputs;