* [PATCH v2] drm/virtio: Extend blob UAPI with deferred-mapping hinting
@ 2026-05-01 0:00 Dmitry Osipenko
2026-05-13 22:10 ` Dmitry Osipenko
0 siblings, 1 reply; 2+ messages in thread
From: Dmitry Osipenko @ 2026-05-01 0:00 UTC (permalink / raw)
To: David Airlie, Gerd Hoffmann, Gurchetan Singh, Chia-I Wu,
Pierre-Eric Pelloux-Prayer, Alyssa Rosenzweig
Cc: Rob Clark, dri-devel, virtualization, linux-kernel, kernel,
Nagapuri Ramesh
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>
---
Changelog:
v2: Rebased on recent kernel. Intel i915 native ctx landed to Mesa, lets to
proceed with merging the mapping hint as a first user of the feature.
drivers/gpu/drm/virtio/virtgpu_drv.h | 2 ++
drivers/gpu/drm/virtio/virtgpu_ioctl.c | 1 +
drivers/gpu/drm/virtio/virtgpu_vram.c | 30 +++++++++++++++++++++-----
include/uapi/drm/virtgpu_drm.h | 4 ++++
4 files changed, 32 insertions(+), 5 deletions(-)
diff --git a/drivers/gpu/drm/virtio/virtgpu_drv.h b/drivers/gpu/drm/virtio/virtgpu_drv.h
index f17660a71a3e..6f49213e23f8 100644
--- 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 c33c057365f8..01daa72b1310 100644
--- 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 084e80227433..4ae3cbc35dd3 100644
--- 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 9debb320c34b..ba09a4ee3e77 100644
--- 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
--
2.53.0
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH v2] drm/virtio: Extend blob UAPI with deferred-mapping hinting
2026-05-01 0:00 [PATCH v2] drm/virtio: Extend blob UAPI with deferred-mapping hinting Dmitry Osipenko
@ 2026-05-13 22:10 ` Dmitry Osipenko
0 siblings, 0 replies; 2+ messages in thread
From: Dmitry Osipenko @ 2026-05-13 22:10 UTC (permalink / raw)
To: David Airlie, Gerd Hoffmann, Gurchetan Singh, Chia-I Wu,
Pierre-Eric Pelloux-Prayer, Alyssa Rosenzweig
Cc: Rob Clark, dri-devel, virtualization, linux-kernel, kernel,
Nagapuri Ramesh
On 5/1/26 03:00, Dmitry Osipenko wrote:
> 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>
> ---
>
> Changelog:
>
> v2: Rebased on recent kernel. Intel i915 native ctx landed to Mesa, lets to
> proceed with merging the mapping hint as a first user of the feature.
>
> drivers/gpu/drm/virtio/virtgpu_drv.h | 2 ++
> drivers/gpu/drm/virtio/virtgpu_ioctl.c | 1 +
> drivers/gpu/drm/virtio/virtgpu_vram.c | 30 +++++++++++++++++++++-----
> include/uapi/drm/virtgpu_drm.h | 4 ++++
> 4 files changed, 32 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/virtio/virtgpu_drv.h b/drivers/gpu/drm/virtio/virtgpu_drv.h
> index f17660a71a3e..6f49213e23f8 100644
> --- 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 c33c057365f8..01daa72b1310 100644
> --- 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 084e80227433..4ae3cbc35dd3 100644
> --- 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 9debb320c34b..ba09a4ee3e77 100644
> --- 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
Applied patch to misc-next
--
Best regards,
Dmitry
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