Re: [PATCH 1/1] drm/virtio: Implement RESOURCE_GET_LAYOUT ioctl

[Zhang, Julia]

On 2024/1/10 18:47, Daniel Vetter wrote:
> On Thu, Dec 21, 2023 at 06:00:16PM +0800, Julia Zhang wrote:
>> From: Daniel Stone <daniels@xxxxxxxxxxxxx>
>>
>> Add a new ioctl to allow the guest VM to discover how the guest
>> actually allocated the underlying buffer, which allows buffers to
>> be used for GL<->Vulkan interop and through standard window systems.
>> It's also a step towards properly supporting modifiers in the guest.
>>
>> Signed-off-by: Daniel Stone <daniels@xxxxxxxxxxxxx>
>> Co-developed-by: Julia Zhang <julia.zhang@xxxxxxx> # support query
>> stride before it's created
>> Signed-off-by: Julia Zhang <julia.zhang@xxxxxxx>
>> ---
>>  drivers/gpu/drm/virtio/virtgpu_drv.c   |  1 +
>>  drivers/gpu/drm/virtio/virtgpu_drv.h   | 22 ++++++++-
>>  drivers/gpu/drm/virtio/virtgpu_ioctl.c | 66 ++++++++++++++++++++++++++
>>  drivers/gpu/drm/virtio/virtgpu_kms.c   |  8 +++-
>>  drivers/gpu/drm/virtio/virtgpu_vq.c    | 63 ++++++++++++++++++++++++
>>  include/uapi/drm/virtgpu_drm.h         | 21 ++++++++
>>  include/uapi/linux/virtio_gpu.h        | 30 ++++++++++++
>>  7 files changed, 208 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/virtio/virtgpu_drv.c b/drivers/gpu/drm/virtio/virtgpu_drv.c
>> index 4334c7608408..98061b714b98 100644
>> --- a/drivers/gpu/drm/virtio/virtgpu_drv.c
>> +++ b/drivers/gpu/drm/virtio/virtgpu_drv.c
>> @@ -148,6 +148,7 @@ static unsigned int features[] = {
>>  	VIRTIO_GPU_F_RESOURCE_UUID,
>>  	VIRTIO_GPU_F_RESOURCE_BLOB,
>>  	VIRTIO_GPU_F_CONTEXT_INIT,
>> +	VIRTIO_GPU_F_RESOURCE_QUERY_LAYOUT,
>>  };
>>  static struct virtio_driver virtio_gpu_driver = {
>>  	.feature_table = features,
>> diff --git a/drivers/gpu/drm/virtio/virtgpu_drv.h b/drivers/gpu/drm/virtio/virtgpu_drv.h
>> index 96365a772f77..bb5edcfeda54 100644
>> --- a/drivers/gpu/drm/virtio/virtgpu_drv.h
>> +++ b/drivers/gpu/drm/virtio/virtgpu_drv.h
>> @@ -214,6 +214,16 @@ struct virtio_gpu_drv_cap_cache {
>>  	atomic_t is_valid;
>>  };
>>  
>> +struct virtio_gpu_query_info {
>> +	uint32_t num_planes;
>> +	uint64_t modifier;
>> +	struct {
>> +		uint64_t offset;
>> +		uint32_t stride;
>> +	} planes[VIRTIO_GPU_MAX_RESOURCE_PLANES];
>> +	atomic_t is_valid;
>> +};
>> +
>>  struct virtio_gpu_device {
>>  	struct drm_device *ddev;
>>  
>> @@ -246,6 +256,7 @@ struct virtio_gpu_device {
>>  	bool has_resource_blob;
>>  	bool has_host_visible;
>>  	bool has_context_init;
>> +	bool has_resource_query_layout;
>>  	struct virtio_shm_region host_visible_region;
>>  	struct drm_mm host_visible_mm;
>>  
>> @@ -277,7 +288,7 @@ struct virtio_gpu_fpriv {
>>  };
>>  
>>  /* virtgpu_ioctl.c */
>> -#define DRM_VIRTIO_NUM_IOCTLS 12
>> +#define DRM_VIRTIO_NUM_IOCTLS 13
>>  extern struct drm_ioctl_desc virtio_gpu_ioctls[DRM_VIRTIO_NUM_IOCTLS];
>>  void virtio_gpu_create_context(struct drm_device *dev, struct drm_file *file);
>>  
>> @@ -420,6 +431,15 @@ virtio_gpu_cmd_set_scanout_blob(struct virtio_gpu_device *vgdev,
>>  				uint32_t width, uint32_t height,
>>  				uint32_t x, uint32_t y);
>>  
>> +int
>> +virtio_gpu_cmd_get_resource_layout(struct virtio_gpu_device *vgdev,
>> +				   struct virtio_gpu_query_info *bo_info,
>> +				   uint32_t width,
>> +				   uint32_t height,
>> +				   uint32_t format,
>> +				   uint32_t bind,
>> +				   uint32_t hw_res_handle);
>> +
>>  /* virtgpu_display.c */
>>  int virtio_gpu_modeset_init(struct virtio_gpu_device *vgdev);
>>  void virtio_gpu_modeset_fini(struct virtio_gpu_device *vgdev);
>> diff --git a/drivers/gpu/drm/virtio/virtgpu_ioctl.c b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
>> index b24b11f25197..216c04314177 100644
>> --- a/drivers/gpu/drm/virtio/virtgpu_ioctl.c
>> +++ b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
>> @@ -107,6 +107,9 @@ static int virtio_gpu_getparam_ioctl(struct drm_device *dev, void *data,
>>  	case VIRTGPU_PARAM_SUPPORTED_CAPSET_IDs:
>>  		value = vgdev->capset_id_mask;
>>  		break;
>> +	case VIRTGPU_PARAM_RESOURCE_QUERY_LAYOUT:
>> +		value = vgdev->has_resource_query_layout ? 1 : 0;
>> +		break;
>>  	default:
>>  		return -EINVAL;
>>  	}
>> @@ -668,6 +671,65 @@ static int virtio_gpu_context_init_ioctl(struct drm_device *dev,
>>  	return ret;
>>  }
>>  
>> +static int virtio_gpu_resource_query_layout_ioctl(struct drm_device *dev,
>> +						  void *data,
>> +						  struct drm_file *file)
>> +{
>> +	struct drm_virtgpu_resource_query_layout *args = data;
>> +	struct virtio_gpu_device *vgdev = dev->dev_private;
>> +	struct drm_gem_object *obj = NULL;
>> +	struct virtio_gpu_object *bo = NULL;
>> +	struct virtio_gpu_query_info bo_info = {0};
>> +	int ret = 0;
>> +	int i;
>> +
>> +	if (!vgdev->has_resource_query_layout) {
>> +		DRM_ERROR("failing: no RQL on host\n");
>> +		return -EINVAL;
>> +	}
>> +
>> +	if (args->handle > 0) {
>> +		obj = drm_gem_object_lookup(file, args->handle);
>> +		if (obj == NULL) {
>> +			DRM_ERROR("invalid handle 0x%x\n", args->handle);
>> +			return -ENOENT;
>> +		}
>> +		bo = gem_to_virtio_gpu_obj(obj);
>> +	}
>> +
>> +	ret = virtio_gpu_cmd_get_resource_layout(vgdev, &bo_info, args->width,
>> +						 args->height, args->format,
>> +						 args->bind, bo ? bo->hw_res_handle : 0);
>> +	if (ret)
>> +		goto out;
>> +
>> +	ret = wait_event_timeout(vgdev->resp_wq,
>> +				 atomic_read(&bo_info.is_valid),
>> +				 5 * HZ);
>> +	if (!ret)
>> +		goto out;
>> +
>> +valid:
>> +	smp_rmb();
> 
> Please, please no hand-rolling of coherency/synchronization primitives
> without writing an entire paper about why this is correct.
> 
> I've done a full-length talk about this:
> 
> https://blog.ffwll.ch/2023/07/eoss-prague-locking-engineering.html
> 
> See the "Level 3: Lockless Tricks" section here:
> 
> https://blog.ffwll.ch/2022/08/locking-hierarchy.html
> 
> To fix this please just use a struct completion, which is practically what
> you hand-roll here.
> 
> Since I looked, on the patch itself: It would be good to add a lot more
> context to this, like the userspace work and why exactly the kernel has to
> be in the business of knowing all this stuff. Because generally it really
> should not, ever: Userspace allocates buffers, userspace better knows how
> it allocated its buffers and should share that through userspace protocol
> (like wayland linux-dmabuf or x11 dri2/3). Why virtio breaks this needs a
> big explainer imo.

Yes I see your point, thank you very much. 

Actually we are going to implement another way to get those information by
using existing submit_cmd ioctl of virtio gpu driver. We will create a buffer
in guest mesa to pass and get information between host and guest. So these
patches can be dropped.

Regards,
Julia

> 
> Thanks, Sima
> 
>> +	WARN_ON(atomic_read(&bo_info.is_valid));
>> +	args->num_planes = bo_info.num_planes;
>> +	args->modifier = bo_info.modifier;
>> +	for (i = 0; i < args->num_planes; i++) {
>> +		args->planes[i].offset = bo_info.planes[i].offset;
>> +		args->planes[i].stride = bo_info.planes[i].stride;
>> +	}
>> +	for (; i < VIRTIO_GPU_MAX_RESOURCE_PLANES; i++) {
>> +		args->planes[i].offset = 0;
>> +		args->planes[i].stride = 0;
>> +	}
>> +	ret = 0;
>> +
>> +out:
>> +	if (obj)
>> +		drm_gem_object_put(obj);
>> +	return ret;
>> +}
>> +
>>  struct drm_ioctl_desc virtio_gpu_ioctls[DRM_VIRTIO_NUM_IOCTLS] = {
>>  	DRM_IOCTL_DEF_DRV(VIRTGPU_MAP, virtio_gpu_map_ioctl,
>>  			  DRM_RENDER_ALLOW),
>> @@ -707,4 +769,8 @@ struct drm_ioctl_desc virtio_gpu_ioctls[DRM_VIRTIO_NUM_IOCTLS] = {
>>  
>>  	DRM_IOCTL_DEF_DRV(VIRTGPU_CONTEXT_INIT, virtio_gpu_context_init_ioctl,
>>  			  DRM_RENDER_ALLOW),
>> +
>> +	DRM_IOCTL_DEF_DRV(VIRTGPU_RESOURCE_QUERY_LAYOUT,
>> +			  virtio_gpu_resource_query_layout_ioctl,
>> +			  DRM_RENDER_ALLOW),
>>  };
>> diff --git a/drivers/gpu/drm/virtio/virtgpu_kms.c b/drivers/gpu/drm/virtio/virtgpu_kms.c
>> index 5a3b5aaed1f3..4f34f4145910 100644
>> --- a/drivers/gpu/drm/virtio/virtgpu_kms.c
>> +++ b/drivers/gpu/drm/virtio/virtgpu_kms.c
>> @@ -175,6 +175,9 @@ int virtio_gpu_init(struct virtio_device *vdev, struct drm_device *dev)
>>  	if (virtio_has_feature(vgdev->vdev, VIRTIO_GPU_F_RESOURCE_BLOB)) {
>>  		vgdev->has_resource_blob = true;
>>  	}
>> +	if (virtio_has_feature(vgdev->vdev, VIRTIO_GPU_F_RESOURCE_QUERY_LAYOUT)) {
>> +		vgdev->has_resource_query_layout = true;
>> +	}
>>  	if (virtio_get_shm_region(vgdev->vdev, &vgdev->host_visible_region,
>>  				  VIRTIO_GPU_SHM_ID_HOST_VISIBLE)) {
>>  		if (!devm_request_mem_region(&vgdev->vdev->dev,
>> @@ -204,8 +207,9 @@ int virtio_gpu_init(struct virtio_device *vdev, struct drm_device *dev)
>>  		 vgdev->has_resource_blob ? '+' : '-',
>>  		 vgdev->has_host_visible ? '+' : '-');
>>  
>> -	DRM_INFO("features: %ccontext_init\n",
>> -		 vgdev->has_context_init ? '+' : '-');
>> +	DRM_INFO("features: %ccontext_init %cresource_query_layout\n",
>> +		 vgdev->has_context_init ? '+' : '-',
>> +		 vgdev->has_resource_query_layout ? '+' : '-');
>>  
>>  	ret = virtio_find_vqs(vgdev->vdev, 2, vqs, callbacks, names, NULL);
>>  	if (ret) {
>> diff --git a/drivers/gpu/drm/virtio/virtgpu_vq.c b/drivers/gpu/drm/virtio/virtgpu_vq.c
>> index b1a00c0c25a7..26998a3ac4c2 100644
>> --- a/drivers/gpu/drm/virtio/virtgpu_vq.c
>> +++ b/drivers/gpu/drm/virtio/virtgpu_vq.c
>> @@ -1302,3 +1302,66 @@ void virtio_gpu_cmd_set_scanout_blob(struct virtio_gpu_device *vgdev,
>>  
>>  	virtio_gpu_queue_ctrl_buffer(vgdev, vbuf);
>>  }
>> +
>> +static void virtio_gpu_cmd_get_resource_layout_cb(struct virtio_gpu_device *vgdev,
>> +						  struct virtio_gpu_vbuffer *vbuf)
>> +{
>> +	struct virtio_gpu_resp_resource_layout *resp =
>> +		(struct virtio_gpu_resp_resource_layout *)vbuf->resp_buf;
>> +	struct virtio_gpu_query_info *bo_info = vbuf->resp_cb_data;
>> +	int i;
>> +
>> +	vbuf->resp_cb_data = NULL;
>> +
>> +	if (resp->hdr.type != VIRTIO_GPU_RESP_OK_RESOURCE_LAYOUT) {
>> +		atomic_set(&bo_info->is_valid, 0);
>> +		goto out;
>> +	}
>> +
>> +	bo_info->modifier = le64_to_cpu(resp->modifier);
>> +	bo_info->num_planes = le32_to_cpu(resp->num_planes);
>> +	for (i = 0; i < bo_info->num_planes; i++) {
>> +		bo_info->planes[i].stride = le32_to_cpu(resp->planes[i].stride);
>> +		bo_info->planes[i].offset = le32_to_cpu(resp->planes[i].offset);
>> +	}
>> +	smp_wmb();
>> +	atomic_set(&bo_info->is_valid, 1);
>> +
>> +out:
>> +	wake_up_all(&vgdev->resp_wq);
>> +}
>> +
>> +int virtio_gpu_cmd_get_resource_layout(struct virtio_gpu_device *vgdev,
>> +				       struct virtio_gpu_query_info *bo_info,
>> +				       uint32_t width,
>> +				       uint32_t height,
>> +				       uint32_t format,
>> +				       uint32_t bind,
>> +				       uint32_t hw_res_handle)
>> +{
>> +	struct virtio_gpu_resource_query_layout *cmd_p;
>> +	struct virtio_gpu_vbuffer *vbuf;
>> +	void *resp_buf;
>> +
>> +	resp_buf = kzalloc(sizeof(struct virtio_gpu_resp_resource_layout),
>> +			   GFP_KERNEL);
>> +	if (!resp_buf)
>> +		return -ENOMEM;
>> +
>> +	cmd_p = virtio_gpu_alloc_cmd_resp
>> +		(vgdev, &virtio_gpu_cmd_get_resource_layout_cb, &vbuf,
>> +		 sizeof(*cmd_p), sizeof(struct virtio_gpu_resp_resource_layout),
>> +		 resp_buf);
>> +	memset(cmd_p, 0, sizeof(*cmd_p));
>> +
>> +	cmd_p->hdr.type = cpu_to_le32(VIRTIO_GPU_CMD_RESOURCE_QUERY_LAYOUT);
>> +	cmd_p->resource_id = cpu_to_le32(hw_res_handle);
>> +	cmd_p->width = cpu_to_le32(width);
>> +	cmd_p->height = cpu_to_le32(height);
>> +	cmd_p->format = cpu_to_le32(format);
>> +	cmd_p->bind = cpu_to_le32(bind);
>> +	vbuf->resp_cb_data = bo_info;
>> +
>> +	virtio_gpu_queue_ctrl_buffer(vgdev, vbuf);
>> +	return 0;
>> +}
>> diff --git a/include/uapi/drm/virtgpu_drm.h b/include/uapi/drm/virtgpu_drm.h
>> index b1d0e56565bc..66f7c0fa1d4d 100644
>> --- a/include/uapi/drm/virtgpu_drm.h
>> +++ b/include/uapi/drm/virtgpu_drm.h
>> @@ -48,6 +48,7 @@ extern "C" {
>>  #define DRM_VIRTGPU_GET_CAPS  0x09
>>  #define DRM_VIRTGPU_RESOURCE_CREATE_BLOB 0x0a
>>  #define DRM_VIRTGPU_CONTEXT_INIT 0x0b
>> +#define DRM_VIRTGPU_RESOURCE_QUERY_LAYOUT 0x0c
>>  
>>  #define VIRTGPU_EXECBUF_FENCE_FD_IN	0x01
>>  #define VIRTGPU_EXECBUF_FENCE_FD_OUT	0x02
>> @@ -97,6 +98,7 @@ struct drm_virtgpu_execbuffer {
>>  #define VIRTGPU_PARAM_CROSS_DEVICE 5 /* Cross virtio-device resource sharing  */
>>  #define VIRTGPU_PARAM_CONTEXT_INIT 6 /* DRM_VIRTGPU_CONTEXT_INIT */
>>  #define VIRTGPU_PARAM_SUPPORTED_CAPSET_IDs 7 /* Bitmask of supported capability set ids */
>> +#define VIRTGPU_PARAM_RESOURCE_QUERY_LAYOUT 8 /* DRM_VIRTGPU_RESOURCE_QUERY_LAYOUT (also needs cap) */
>>  
>>  struct drm_virtgpu_getparam {
>>  	__u64 param;
>> @@ -211,6 +213,21 @@ struct drm_virtgpu_context_init {
>>  	__u64 ctx_set_params;
>>  };
>>  
>> +#define VIRTIO_GPU_MAX_RESOURCE_PLANES 4
>> +struct drm_virtgpu_resource_query_layout {
>> +	__u32 handle;
>> +	__u32 width;
>> +	__u32 height;
>> +	__u32 format;
>> +	__u32 bind;
>> +	__u32 num_planes;
>> +	__u64 modifier;
>> +	struct {
>> +		__u64 offset;
>> +		__u32 stride;
>> +	} planes[VIRTIO_GPU_MAX_RESOURCE_PLANES];
>> +};
>> +
>>  /*
>>   * Event code that's given when VIRTGPU_CONTEXT_PARAM_POLL_RINGS_MASK is in
>>   * effect.  The event size is sizeof(drm_event), since there is no additional
>> @@ -261,6 +278,10 @@ struct drm_virtgpu_context_init {
>>  	DRM_IOWR(DRM_COMMAND_BASE + DRM_VIRTGPU_CONTEXT_INIT,		\
>>  		struct drm_virtgpu_context_init)
>>  
>> +#define DRM_IOCTL_VIRTGPU_RESOURCE_QUERY_LAYOUT				\
>> +	DRM_IOWR(DRM_COMMAND_BASE + DRM_VIRTGPU_RESOURCE_QUERY_LAYOUT,	\
>> +		struct drm_virtgpu_resource_query_layout)
>> +
>>  #if defined(__cplusplus)
>>  }
>>  #endif
>> diff --git a/include/uapi/linux/virtio_gpu.h b/include/uapi/linux/virtio_gpu.h
>> index f556fde07b76..547575232376 100644
>> --- a/include/uapi/linux/virtio_gpu.h
>> +++ b/include/uapi/linux/virtio_gpu.h
>> @@ -65,6 +65,11 @@
>>   */
>>  #define VIRTIO_GPU_F_CONTEXT_INIT        4
>>  
>> +/*
>> + * VIRTIO_GPU_CMD_RESOURCE_QUERY_LAYOUT
>> + */
>> +#define VIRTIO_GPU_F_RESOURCE_QUERY_LAYOUT 5
>> +
>>  enum virtio_gpu_ctrl_type {
>>  	VIRTIO_GPU_UNDEFINED = 0,
>>  
>> @@ -95,6 +100,7 @@ enum virtio_gpu_ctrl_type {
>>  	VIRTIO_GPU_CMD_SUBMIT_3D,
>>  	VIRTIO_GPU_CMD_RESOURCE_MAP_BLOB,
>>  	VIRTIO_GPU_CMD_RESOURCE_UNMAP_BLOB,
>> +	VIRTIO_GPU_CMD_RESOURCE_QUERY_LAYOUT,
>>  
>>  	/* cursor commands */
>>  	VIRTIO_GPU_CMD_UPDATE_CURSOR = 0x0300,
>> @@ -108,6 +114,7 @@ enum virtio_gpu_ctrl_type {
>>  	VIRTIO_GPU_RESP_OK_EDID,
>>  	VIRTIO_GPU_RESP_OK_RESOURCE_UUID,
>>  	VIRTIO_GPU_RESP_OK_MAP_INFO,
>> +	VIRTIO_GPU_RESP_OK_RESOURCE_LAYOUT,
>>  
>>  	/* error responses */
>>  	VIRTIO_GPU_RESP_ERR_UNSPEC = 0x1200,
>> @@ -453,4 +460,27 @@ struct virtio_gpu_resource_unmap_blob {
>>  	__le32 padding;
>>  };
>>  
>> +/* VIRTIO_GPU_CMD_RESOURCE_QUERY_LAYOUT */
>> +struct virtio_gpu_resource_query_layout {
>> +	struct virtio_gpu_ctrl_hdr hdr;
>> +	__le32 resource_id;
>> +	__le32 width;
>> +	__le32 height;
>> +	__le32 format;
>> +	__le32 bind;
>> +};
>> +
>> +
>> +/* VIRTIO_GPU_RESP_OK_RESOURCE_LAYOUT */
>> +#define VIRTIO_GPU_RES_MAX_PLANES 4
>> +struct virtio_gpu_resp_resource_layout {
>> +	struct virtio_gpu_ctrl_hdr hdr;
>> +	__le64 modifier;
>> +	__le32 num_planes;
>> +	struct virtio_gpu_resource_plane {
>> +		__le64 offset;
>> +		__le32 stride;
>> +	} planes[VIRTIO_GPU_RES_MAX_PLANES];
>> +};
>> +
>>  #endif
>> -- 
>> 2.34.1
>>
>