[PATCH v2 1/1] drm/syncobj: add sideband payload

Lionel Landwerlin lionel.g.landwerlin at intel.com
Thu Aug 8 09:42:58 UTC 2019


On 08/08/2019 12:32, Koenig, Christian wrote:
> Am 08.08.19 um 11:04 schrieb Lionel Landwerlin:
>> The Vulkan timeline semaphores allow signaling to happen on the point
>> of the timeline without all of the its dependencies to be created.
>>
>> The current 2 implementations (AMD/Intel) of the Vulkan spec on top of
>> the Linux kernel are using a thread to wait on the dependencies of a
>> given point to materialize and delay actual submission to the kernel
>> driver until the wait completes.
>>
>> If a binary semaphore is submitted for signaling along the side of a
>> timeline semaphore waiting for completion that means that the drm
>> syncobj associated with that binary semaphore will not have a DMA
>> fence associated with it by the time vkQueueSubmit() returns. This and
>> the fact that a binary semaphore can be signaled and unsignaled as
>> before its DMA fences materialize mean that we cannot just rely on the
>> fence within the syncobj but we also need a sideband payload verifying
>> that the fence in the syncobj matches the last submission from the
>> Vulkan API point of view.
>>
>> This change adds a sideband payload that is incremented with signaled
>> syncobj when vkQueueSubmit() is called. The next vkQueueSubmit()
>> waiting on a the syncobj will read the sideband payload and wait for a
>> fence chain element with a seqno superior or equal to the sideband
>> payload value to be added into the fence chain and use that fence to
>> trigger the submission on the kernel driver.
>>
>> v2: Use a separate ioctl to get/set the sideband value (Christian)
>>
>> Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin at intel.com>
>> Cc: Christian Koenig <Christian.Koenig at amd.com>
>> Cc: Jason Ekstrand <jason at jlekstrand.net>
>> Cc: David(ChunMing) Zhou <David1.Zhou at amd.com>
>> ---
>>    drivers/gpu/drm/drm_internal.h |  2 ++
>>    drivers/gpu/drm/drm_ioctl.c    |  3 ++
>>    drivers/gpu/drm/drm_syncobj.c  | 63 +++++++++++++++++++++++++++++++---
>>    include/drm/drm_syncobj.h      |  9 +++++
>>    include/uapi/drm/drm.h         |  5 ++-
>>    5 files changed, 77 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/drm_internal.h b/drivers/gpu/drm/drm_internal.h
>> index 51a2055c8f18..de5267711a7c 100644
>> --- a/drivers/gpu/drm/drm_internal.h
>> +++ b/drivers/gpu/drm/drm_internal.h
>> @@ -208,6 +208,8 @@ int drm_syncobj_timeline_signal_ioctl(struct drm_device *dev, void *data,
>>    				      struct drm_file *file_private);
>>    int drm_syncobj_query_ioctl(struct drm_device *dev, void *data,
>>    			    struct drm_file *file_private);
>> +int drm_syncobj_sideband_ioctl(struct drm_device *dev, void *data,
>> +			       struct drm_file *file_private);
>>    
>>    /* drm_framebuffer.c */
>>    void drm_framebuffer_print_info(struct drm_printer *p, unsigned int indent,
>> diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c
>> index f675a3bb2c88..7fd99533f78f 100644
>> --- a/drivers/gpu/drm/drm_ioctl.c
>> +++ b/drivers/gpu/drm/drm_ioctl.c
>> @@ -703,6 +703,9 @@ static const struct drm_ioctl_desc drm_ioctls[] = {
>>    		      DRM_RENDER_ALLOW),
>>    	DRM_IOCTL_DEF(DRM_IOCTL_SYNCOBJ_QUERY, drm_syncobj_query_ioctl,
>>    		      DRM_RENDER_ALLOW),
>> +	DRM_IOCTL_DEF(DRM_IOCTL_SYNCOBJ_SIDEBAND, drm_syncobj_sideband_ioctl,
>> +		      DRM_RENDER_ALLOW),
>> +
>>    	DRM_IOCTL_DEF(DRM_IOCTL_CRTC_GET_SEQUENCE, drm_crtc_get_sequence_ioctl, 0),
>>    	DRM_IOCTL_DEF(DRM_IOCTL_CRTC_QUEUE_SEQUENCE, drm_crtc_queue_sequence_ioctl, 0),
>>    	DRM_IOCTL_DEF(DRM_IOCTL_MODE_CREATE_LEASE, drm_mode_create_lease_ioctl, DRM_MASTER),
>> diff --git a/drivers/gpu/drm/drm_syncobj.c b/drivers/gpu/drm/drm_syncobj.c
>> index b927e482e554..66f4f91baa6d 100644
>> --- a/drivers/gpu/drm/drm_syncobj.c
>> +++ b/drivers/gpu/drm/drm_syncobj.c
>> @@ -1150,8 +1150,10 @@ drm_syncobj_reset_ioctl(struct drm_device *dev, void *data,
>>    	if (ret < 0)
>>    		return ret;
>>    
>> -	for (i = 0; i < args->count_handles; i++)
>> +	for (i = 0; i < args->count_handles; i++) {
>>    		drm_syncobj_replace_fence(syncobjs[i], NULL);
>> +		syncobjs[i]->sideband_payload = 0;
>> +	}
>>    
>>    	drm_syncobj_array_free(syncobjs, args->count_handles);
>>    
>> @@ -1205,7 +1207,7 @@ drm_syncobj_timeline_signal_ioctl(struct drm_device *dev, void *data,
>>    	if (!drm_core_check_feature(dev, DRIVER_SYNCOBJ_TIMELINE))
>>    		return -EOPNOTSUPP;
>>    
>> -	if (args->pad != 0)
>> +	if (args->flags != 0)
>>    		return -EINVAL;
>>    
>>    	if (args->count_handles == 0)
>> @@ -1276,7 +1278,7 @@ int drm_syncobj_query_ioctl(struct drm_device *dev, void *data,
>>    	if (!drm_core_check_feature(dev, DRIVER_SYNCOBJ_TIMELINE))
>>    		return -EOPNOTSUPP;
>>    
>> -	if (args->pad != 0)
>> +	if (args->flags != 0)
>>    		return -EINVAL;
>>    
>>    	if (args->count_handles == 0)
>> @@ -1312,15 +1314,68 @@ int drm_syncobj_query_ioctl(struct drm_device *dev, void *data,
>>    			point = dma_fence_is_signaled(last_signaled) ?
>>    				last_signaled->seqno :
>>    				to_dma_fence_chain(last_signaled)->prev_seqno;
>> -			dma_fence_put(last_signaled);
>> +				dma_fence_put(last_signaled);


Whoops, I need to drop this.


>>    		} else {
>>    			point = 0;
>>    		}
>>    		ret = copy_to_user(&points[i], &point, sizeof(uint64_t));
>>    		ret = ret ? -EFAULT : 0;
>>    		if (ret)
>> +			goto error;
>> +		break;
>> +	}
>> +
>> +error:
>> +	drm_syncobj_array_free(syncobjs, args->count_handles);
>> +
>> +	return ret;
>> +}
> Those changes above to drm_syncobj_query now look completely unrelated
> to me.


The diff is really weird indeed but apart from the mistake above it's right.


>
>> +
>> +int drm_syncobj_sideband_ioctl(struct drm_device *dev, void *data,
>> +			       struct drm_file *file_private)
>> +{
>> +	struct drm_syncobj_timeline_array *args = data;
>> +	struct drm_syncobj **syncobjs;
>> +	uint64_t __user *points = u64_to_user_ptr(args->points);
>> +	uint32_t i;
>> +	int ret;
>> +
>> +	if (!drm_core_check_feature(dev, DRIVER_SYNCOBJ_TIMELINE))
>> +		return -EOPNOTSUPP;
>> +
>> +	if (args->flags != DRM_SYNCOBJ_TIMELINE_ARRAY_GET_SIDEBAND_PAYLOAD &&
>> +	    args->flags != DRM_SYNCOBJ_TIMELINE_ARRAY_SET_SIDEBAND_PAYLOAD)
>> +		return -EINVAL;
>> +
>> +	if (args->count_handles == 0)
>> +		return -EINVAL;
>> +
>> +	ret = drm_syncobj_array_find(file_private,
>> +				     u64_to_user_ptr(args->handles),
>> +				     args->count_handles,
>> +				     &syncobjs);
>> +	if (ret < 0)
>> +		return ret;
>> +
>> +	for (i = 0; i < args->count_handles; i++) {
>> +		switch (args->flags) {
>> +		case DRM_SYNCOBJ_TIMELINE_ARRAY_GET_SIDEBAND_PAYLOAD:
>> +			copy_to_user(&points[i], &syncobjs[i]->sideband_payload, sizeof(uint64_t));
>> +			ret = ret ? -EFAULT : 0;
>> +			if (ret)
>> +				goto error;
>> +			break;
>> +
>> +		case DRM_SYNCOBJ_TIMELINE_ARRAY_SET_SIDEBAND_PAYLOAD:
>> +			copy_from_user(&syncobjs[i]->sideband_payload, &points[i], sizeof(uint64_t));
>> +			ret = ret ? -EFAULT : 0;
>> +			if (ret)
>> +				goto error;
>>    			break;
>> +		}
>>    	}
>> +
>> +error:
>>    	drm_syncobj_array_free(syncobjs, args->count_handles);
>>    
>>    	return ret;
>> diff --git a/include/drm/drm_syncobj.h b/include/drm/drm_syncobj.h
>> index 6cf7243a1dc5..b587b8e07547 100644
>> --- a/include/drm/drm_syncobj.h
>> +++ b/include/drm/drm_syncobj.h
>> @@ -61,6 +61,15 @@ struct drm_syncobj {
>>    	 * @file: A file backing for this syncobj.
>>    	 */
>>    	struct file *file;
>> +	/**
>> +	 * @sideband_payload: A 64bit side band payload.
>> +	 *
>> +	 * We use the sideband payload value to wait on binary syncobj fences
>> +	 * to materialize. It is a reservation mechanism for the signaler to
>> +	 * express that at some point in the future a dma fence with the same
>> +	 * seqno will be put into the syncobj.
>> +	 */
>> +	u64 sideband_payload;
>>    };
>>    
>>    void drm_syncobj_free(struct kref *kref);
>> diff --git a/include/uapi/drm/drm.h b/include/uapi/drm/drm.h
>> index 8a5b2f8f8eb9..dfcbaf603aff 100644
>> --- a/include/uapi/drm/drm.h
>> +++ b/include/uapi/drm/drm.h
>> @@ -782,7 +782,9 @@ struct drm_syncobj_timeline_array {
>>    	__u64 handles;
>>    	__u64 points;
>>    	__u32 count_handles;
>> -	__u32 pad;
>> +	__u32 flags;
>> +#define DRM_SYNCOBJ_TIMELINE_ARRAY_GET_SIDEBAND_PAYLOAD (0)
>> +#define DRM_SYNCOBJ_TIMELINE_ARRAY_SET_SIDEBAND_PAYLOAD (1)
>>    };
>>    
>>    
>> @@ -946,6 +948,7 @@ extern "C" {
>>    #define DRM_IOCTL_SYNCOBJ_QUERY		DRM_IOWR(0xCB, struct drm_syncobj_timeline_array)
>>    #define DRM_IOCTL_SYNCOBJ_TRANSFER	DRM_IOWR(0xCC, struct drm_syncobj_transfer)
>>    #define DRM_IOCTL_SYNCOBJ_TIMELINE_SIGNAL	DRM_IOWR(0xCD, struct drm_syncobj_timeline_array)
>> +#define DRM_IOCTL_SYNCOBJ_SIDEBAND	DRM_IOWR(0xCE, struct drm_syncobj_timeline_array)
> Maybe better add separate get/set IOCTLs, but just a suggestion.
>
> Regards,
> Christian.


Alright, I was worried about polluting the ioctl IDs.


Did the new tests on the CTS helped reproduce on your side the issue 
this is solving?


Thanks,


-Lionel


>
>>    
>>    /**
>>     * Device specific ioctls should only be in their respective headers




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