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

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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
This commit is contained in:
Dmitry Osipenko 2026-05-01 03:00:43 +03:00
parent d989f135f7
commit 4c26e16294
4 changed files with 32 additions and 5 deletions
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2
drivers/gpu/drm/virtio/virtgpu_drv.h
View File

@ -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,

1
drivers/gpu/drm/virtio/virtgpu_ioctl.c
View File

@ -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;
}

30
drivers/gpu/drm/virtio/virtgpu_vram.c
View File

@ -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);
}

4
include/uapi/drm/virtgpu_drm.h
View File

@ -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