drm/virtio: Extend blob UAPI with deferred-mapping hinting

If userspace never maps GEM object, then BO wastes hostmem space
because VirtIO-GPU driver maps VRAM BO at the BO's creating time.

Make mappings on-demand by adding new RESOURCE_CREATE_BLOB IOCTL/UAPI
hinting flag telling that host mapping should be deferred until first
mapping is made when the flag is set by userspace.

Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Reviewed-by: Rob Clark <robdclark@gmail.com>
Link: https://patch.msgid.link/20260501000043.2483678-1-dmitry.osipenko@collabora.com

diff --git a/drivers/gpu/drm/virtio/virtgpu_drv.h b/drivers/gpu/drm/virtio/virtgpu_drv.h
index f17660a71a3e7a22b5d4fefa6b754c227a294037..6f49213e23f8ee3afe78f29bed52239ccd1d194c 100644 (file)
--- a/drivers/gpu/drm/virtio/virtgpu_drv.h
+++ b/drivers/gpu/drm/virtio/virtgpu_drv.h
@@ -84,6 +84,7 @@ struct virtio_gpu_object_params {
        uint32_t blob_mem;
        uint32_t blob_flags;
        uint64_t blob_id;
+       uint32_t blob_hints;
 };
 
 struct virtio_gpu_object {
@@ -507,6 +508,7 @@ struct sg_table *virtio_gpu_vram_map_dma_buf(struct virtio_gpu_object *bo,
 void virtio_gpu_vram_unmap_dma_buf(struct device *dev,
                                   struct sg_table *sgt,
                                   enum dma_data_direction dir);
+void virtio_gpu_vram_map_deferred(struct virtio_gpu_object_vram *vram);
 
 /* virtgpu_submit.c */
 int virtio_gpu_execbuffer_ioctl(struct drm_device *dev, void *data,

diff --git a/drivers/gpu/drm/virtio/virtgpu_ioctl.c b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
index c33c057365f85a2ace536f91655c903036827312..01daa72b1310e06f2565195246eb742df61050e4 100644 (file)
--- a/drivers/gpu/drm/virtio/virtgpu_ioctl.c
+++ b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
@@ -489,6 +489,7 @@ static int verify_blob(struct virtio_gpu_device *vgdev,
        params->size = rc_blob->size;
        params->blob = true;
        params->blob_flags = rc_blob->blob_flags;
+       params->blob_hints = rc_blob->blob_hints;
        return 0;
 }
 

diff --git a/drivers/gpu/drm/virtio/virtgpu_vram.c b/drivers/gpu/drm/virtio/virtgpu_vram.c
index 084e80227433728f54e1df8ce1847a6241546597..4ae3cbc35dd364368ffa5ae1db818cefc65d2960 100644 (file)
--- a/drivers/gpu/drm/virtio/virtgpu_vram.c
+++ b/drivers/gpu/drm/virtio/virtgpu_vram.c
@@ -3,6 +3,8 @@
 
 #include <linux/dma-mapping.h>
 
+static DEFINE_MUTEX(map_lock);
+
 static void virtio_gpu_vram_free(struct drm_gem_object *obj)
 {
        struct virtio_gpu_object *bo = gem_to_virtio_gpu_obj(obj);
@@ -42,6 +44,11 @@ static int virtio_gpu_vram_mmap(struct drm_gem_object *obj,
        if (!(bo->blob_flags & VIRTGPU_BLOB_FLAG_USE_MAPPABLE))
                return -EINVAL;
 
+       virtio_gpu_vram_map_deferred(vram);
+
+       if (vram->map_state == STATE_INITIALIZING)
+               virtio_gpu_notify(vgdev);
+
        wait_event(vgdev->resp_wq, vram->map_state != STATE_INITIALIZING);
        if (vram->map_state != STATE_OK)
                return -EINVAL;
@@ -218,14 +225,27 @@ int virtio_gpu_vram_create(struct virtio_gpu_device *vgdev,
 
        virtio_gpu_cmd_resource_create_blob(vgdev, &vram->base, params, NULL,
                                            0);
-       if (params->blob_flags & VIRTGPU_BLOB_FLAG_USE_MAPPABLE) {
-               ret = virtio_gpu_vram_map(&vram->base);
-               if (ret) {
-                       virtio_gpu_vram_free(obj);
-                       return ret;
+       if (!(params->blob_hints & DRM_VIRTGPU_BLOB_FLAG_HINT_DEFER_MAPPING)) {
+               if (params->blob_flags & VIRTGPU_BLOB_FLAG_USE_MAPPABLE) {
+                       ret = virtio_gpu_vram_map(&vram->base);
+                       if (ret) {
+                               virtio_gpu_vram_free(obj);
+                               return ret;
+                       }
                }
        }
 
        *bo_ptr = &vram->base;
        return 0;
 }
+
+void virtio_gpu_vram_map_deferred(struct virtio_gpu_object_vram *vram)
+{
+       if (!(vram->base.blob_flags & VIRTGPU_BLOB_FLAG_USE_MAPPABLE))
+               return;
+
+       mutex_lock(&map_lock);
+       if (!drm_mm_node_allocated(&vram->vram_node))
+               virtio_gpu_vram_map(&vram->base);
+       mutex_unlock(&map_lock);
+}

diff --git a/include/uapi/drm/virtgpu_drm.h b/include/uapi/drm/virtgpu_drm.h
index 9debb320c34bec120d38405e8c5f1f09abe1954b..ba09a4ee3e77a713b5df74a0ab0c763cfc022dfc 100644 (file)
--- a/include/uapi/drm/virtgpu_drm.h
+++ b/include/uapi/drm/virtgpu_drm.h
@@ -200,6 +200,10 @@ struct drm_virtgpu_resource_create_blob {
        __u32 cmd_size;
        __u64 cmd;
        __u64 blob_id;
+
+#define DRM_VIRTGPU_BLOB_FLAG_HINT_DEFER_MAPPING        0x0001
+       __u32 blob_hints;
+       __u32 pad2;
 };
 
 #define VIRTGPU_CONTEXT_PARAM_CAPSET_ID       0x0001