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.
Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@xxxxxxxxx>
---
drivers/gpu/drm/drm_syncobj.c | 119 +++++++++++++++++++++-------------
include/drm/drm_syncobj.h | 9 +++
include/uapi/drm/drm.h | 4 +-
3 files changed, 86 insertions(+), 46 deletions(-)
diff --git a/drivers/gpu/drm/drm_syncobj.c b/drivers/gpu/drm/drm_syncobj.c
index b927e482e554..c437fb6aaf7c 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);
@@ -1197,7 +1199,7 @@ drm_syncobj_timeline_signal_ioctl(struct drm_device *dev, void *data,
{
struct drm_syncobj_timeline_array *args = data;
struct drm_syncobj **syncobjs;
- struct dma_fence_chain **chains;
+ struct dma_fence_chain **chains = NULL;
uint64_t *points;
uint32_t i, j;
int ret;
@@ -1205,7 +1207,8 @@ 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->selector != DRM_SYNCOBJ_TIMELINE_ARRAY_SELECTOR_SIGNALED_POINT &&
+ args->selector != DRM_SYNCOBJ_TIMELINE_ARRAY_SELECTOR_SIDEBAND_PAYLOAD)
return -EINVAL;
if (args->count_handles == 0)
@@ -1232,30 +1235,41 @@ drm_syncobj_timeline_signal_ioctl(struct drm_device *dev, void *data,
goto err_points;
}
- chains = kmalloc_array(args->count_handles, sizeof(void *), GFP_KERNEL);
- if (!chains) {
- ret = -ENOMEM;
- goto err_points;
- }
- for (i = 0; i < args->count_handles; i++) {
- chains[i] = kzalloc(sizeof(struct dma_fence_chain), GFP_KERNEL);
- if (!chains[i]) {
- for (j = 0; j < i; j++)
- kfree(chains[j]);
+ switch (args->selector) {
+ case DRM_SYNCOBJ_TIMELINE_ARRAY_SELECTOR_SIGNALED_POINT:
+ chains = kmalloc_array(args->count_handles, sizeof(void *), GFP_KERNEL);
+ if (!chains) {
ret = -ENOMEM;
- goto err_chains;
+ goto err_points;
+ }
+ for (i = 0; i < args->count_handles; i++) {
+ chains[i] = kzalloc(sizeof(struct dma_fence_chain), GFP_KERNEL);
+ if (!chains[i]) {
+ for (j = 0; j < i; j++)
+ kfree(chains[j]);
+ ret = -ENOMEM;
+ goto err_chains;
+ }
}
- }
- for (i = 0; i < args->count_handles; i++) {
- struct dma_fence *fence = dma_fence_get_stub();
+ for (i = 0; i < args->count_handles; i++) {
+ struct dma_fence *fence = dma_fence_get_stub();
- drm_syncobj_add_point(syncobjs[i], chains[i],
- fence, points[i]);
- dma_fence_put(fence);
+ drm_syncobj_add_point(syncobjs[i], chains[i],
+ fence, points[i]);
+ dma_fence_put(fence);
+ }
+ break;
+
+ case DRM_SYNCOBJ_TIMELINE_ARRAY_SELECTOR_SIDEBAND_PAYLOAD:
+ for (i = 0; i < args->count_handles; i++)
+ syncobjs[i]->sideband_payload = points[i];
+ break;
}
+
err_chains:
- kfree(chains);
+ if (chains)
+ kfree(chains);
err_points:
kfree(points);
out:
@@ -1276,7 +1290,8 @@ 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->selector != DRM_SYNCOBJ_TIMELINE_ARRAY_SELECTOR_SIGNALED_POINT &&
+ args->selector != DRM_SYNCOBJ_TIMELINE_ARRAY_SELECTOR_SIDEBAND_PAYLOAD)
return -EINVAL;
if (args->count_handles == 0)
@@ -1290,37 +1305,51 @@ int drm_syncobj_query_ioctl(struct drm_device *dev, void *data,
return ret;
for (i = 0; i < args->count_handles; i++) {
- struct dma_fence_chain *chain;
struct dma_fence *fence;
+ struct dma_fence_chain *chain;
uint64_t point;
- fence = drm_syncobj_fence_get(syncobjs[i]);
- chain = to_dma_fence_chain(fence);
- if (chain) {
- struct dma_fence *iter, *last_signaled = NULL;
-
- dma_fence_chain_for_each(iter, fence) {
- if (iter->context != fence->context) {
- dma_fence_put(iter);
- /* It is most likely that timeline has
- * unorder points. */
- break;
+ switch (args->selector) {
+ case DRM_SYNCOBJ_TIMELINE_ARRAY_SELECTOR_SIGNALED_POINT:
+ fence = drm_syncobj_fence_get(syncobjs[i]);
+ chain = to_dma_fence_chain(fence);
+ if (chain) {
+ struct dma_fence *iter, *last_signaled = NULL;
+
+ dma_fence_chain_for_each(iter, fence) {
+ if (iter->context != fence->context) {
+ dma_fence_put(iter);
+ /* It is most likely that
+ * timeline has unorder
+ * points. */
+ break;
+ }
+ dma_fence_put(last_signaled);
+ last_signaled = dma_fence_get(iter);
}
+ point = dma_fence_is_signaled(last_signaled) ?
+ last_signaled->seqno :
+ to_dma_fence_chain(last_signaled)->prev_seqno;
dma_fence_put(last_signaled);
- last_signaled = dma_fence_get(iter);
+ } else {
+ point = 0;
}
- point = dma_fence_is_signaled(last_signaled) ?
- last_signaled->seqno :
- to_dma_fence_chain(last_signaled)->prev_seqno;
- dma_fence_put(last_signaled);
- } else {
- point = 0;
- }
- ret = copy_to_user(&points[i], &point, sizeof(uint64_t));
- ret = ret ? -EFAULT : 0;
- if (ret)
+ ret = copy_to_user(&points[i], &point, sizeof(uint64_t));
+ ret = ret ? -EFAULT : 0;
+ if (ret)
+ goto error;
+ break;
+
+ case DRM_SYNCOBJ_TIMELINE_ARRAY_SELECTOR_SIDEBAND_PAYLOAD:
+ copy_to_user(&points[i], &syncobjs[i]->sideband_payload, 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..dea759a36d37 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 selector;
+#define DRM_SYNCOBJ_TIMELINE_ARRAY_SELECTOR_SIGNALED_POINT (0)
+#define DRM_SYNCOBJ_TIMELINE_ARRAY_SELECTOR_SIDEBAND_PAYLOAD (1)
};
--
2.23.0.rc1
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