Re: [Linaro-mm-sig] [PATCH v4 07/13] drm/msm: Track "seqno" fences by idr

On Wed, Nov 10, 2021 at 7:28 AM Akhil P Oommen akhilpo@codeaurora.org wrote:

On 7/28/2021 6:36 AM, Rob Clark wrote:

...

From: Rob Clark robdclark@chromium.org

Previously the (non-fd) fence returned from submit ioctl was a raw seqno, which is scoped to the ring. But from UABI standpoint, the ioctls related to seqno fences all specify a submitqueue. We can take advantage of that to replace the seqno fences with a cyclic idr handle.

This is in preperation for moving to drm scheduler, at which point the submit ioctl will return after queuing the submit job to the scheduler, but before the submit is written into the ring (and therefore before a ring seqno has been assigned). Which means we need to replace the dma_fence that userspace may need to wait on with a scheduler fence.

Signed-off-by: Rob Clark robdclark@chromium.org Acked-by: Christian König christian.koenig@amd.com

---

drivers/gpu/drm/msm/msm_drv.c | 30 +++++++++++++++++-- drivers/gpu/drm/msm/msm_fence.c | 42 --------------------------- drivers/gpu/drm/msm/msm_fence.h | 3 -- drivers/gpu/drm/msm/msm_gem.h | 1 + drivers/gpu/drm/msm/msm_gem_submit.c | 23 ++++++++++++++- drivers/gpu/drm/msm/msm_gpu.h | 5 ++++ drivers/gpu/drm/msm/msm_submitqueue.c | 5 ++++ 7 files changed, 61 insertions(+), 48 deletions(-)

diff --git a/drivers/gpu/drm/msm/msm_drv.c b/drivers/gpu/drm/msm/msm_drv.c index 9b8fa2ad0d84..1594ae39d54f 100644 --- a/drivers/gpu/drm/msm/msm_drv.c +++ b/drivers/gpu/drm/msm/msm_drv.c @@ -911,6 +911,7 @@ static int msm_ioctl_wait_fence(struct drm_device *dev, void *data, ktime_t timeout = to_ktime(args->timeout); struct msm_gpu_submitqueue *queue; struct msm_gpu *gpu = priv->gpu;

• struct dma_fence *fence;
  int ret;
  
  if (args->pad) {
  

@@ -925,10 +926,35 @@ static int msm_ioctl_wait_fence(struct drm_device *dev, void *data, if (!queue) return -ENOENT;

• ret = msm_wait_fence(gpu->rb[queue->prio]->fctx, args->fence, &timeout,
  

•         true);
  

• /*
  

•  * Map submitqueue scoped "seqno" (which is actually an idr key)
  

•  * back to underlying dma-fence
  

•  *
  

•  * The fence is removed from the fence_idr when the submit is
  

•  * retired, so if the fence is not found it means there is nothing
  

•  * to wait for
  

•  */
  

• ret = mutex_lock_interruptible(&queue->lock);
  

• if (ret)
  

•         return ret;
  

• fence = idr_find(&queue->fence_idr, args->fence);
  

• if (fence)
  

•         fence = dma_fence_get_rcu(fence);
  

• mutex_unlock(&queue->lock);
  

• if (!fence)
  

•         return 0;
  
  

• ret = dma_fence_wait_timeout(fence, true, timeout_to_jiffies(&timeout));
  

• if (ret == 0) {
  

•         ret = -ETIMEDOUT;
  

• } else if (ret != -ERESTARTSYS) {
  

•         ret = 0;
  

• }
  

• dma_fence_put(fence);
  msm_submitqueue_put(queue);
  

• return ret;
  

  }

diff --git a/drivers/gpu/drm/msm/msm_fence.c b/drivers/gpu/drm/msm/msm_fence.c index b92a9091a1e2..f2cece542c3f 100644 --- a/drivers/gpu/drm/msm/msm_fence.c +++ b/drivers/gpu/drm/msm/msm_fence.c @@ -24,7 +24,6 @@ msm_fence_context_alloc(struct drm_device *dev, volatile uint32_t *fenceptr, strncpy(fctx->name, name, sizeof(fctx->name)); fctx->context = dma_fence_context_alloc(1); fctx->fenceptr = fenceptr;

• init_waitqueue_head(&fctx->event);
  spin_lock_init(&fctx->spinlock);
  
  return fctx;
  

@@ -45,53 +44,12 @@ static inline bool fence_completed(struct msm_fence_context *fctx, uint32_t fenc (int32_t)(*fctx->fenceptr - fence) >= 0; }

-/* legacy path for WAIT_FENCE ioctl: */ -int msm_wait_fence(struct msm_fence_context *fctx, uint32_t fence,

•         ktime_t *timeout, bool interruptible)
  

-{

• int ret;
  

• if (fence > fctx->last_fence) {
  

•         DRM_ERROR_RATELIMITED("%s: waiting on invalid fence: %u (of %u)\n",
  

•                         fctx->name, fence, fctx->last_fence);
  

•         return -EINVAL;
  

Rob, we changed this pre-existing behaviour in this patch. Now, when userspace tries to wait on a future fence, we don't return an error.

I just want to check if this was accidental or not?

Hmm, perhaps we should do this to restore the previous behavior:

------------- diff --git a/drivers/gpu/drm/msm/msm_drv.c b/drivers/gpu/drm/msm/msm_drv.c index 73e827641024..3dd6da56eae6 100644 --- a/drivers/gpu/drm/msm/msm_drv.c +++ b/drivers/gpu/drm/msm/msm_drv.c @@ -1000,8 +1000,12 @@ static int msm_ioctl_wait_fence(struct drm_device *dev, void *data, fence = dma_fence_get_rcu(fence); mutex_unlock(&queue->lock);

- if (!fence) - return 0; + if (!fence) { + struct msm_fence_context *fctx = gpu->rb[queue->ring_nr]->fctx; + DRM_ERROR_RATELIMITED("%s: waiting on invalid fence: %u (of %u)\n", + fctx->name, fence, fctx->last_fence); + return -EINVAL; + }

ret = dma_fence_wait_timeout(fence, true, timeout_to_jiffies(&timeout)); if (ret == 0) { -------------

BR, -R

-Akhil.

...

• }
  

• if (!timeout) {
  

•         /* no-wait: */
  

•         ret = fence_completed(fctx, fence) ? 0 : -EBUSY;
  

• } else {
  

•         unsigned long remaining_jiffies = timeout_to_jiffies(timeout);
  

•         if (interruptible)
  

•                 ret = wait_event_interruptible_timeout(fctx->event,
  

•                         fence_completed(fctx, fence),
  

•                         remaining_jiffies);
  

•         else
  

•                 ret = wait_event_timeout(fctx->event,
  

•                         fence_completed(fctx, fence),
  

•                         remaining_jiffies);
  

•         if (ret == 0) {
  

•                 DBG("timeout waiting for fence: %u (completed: %u)",
  

•                                 fence, fctx->completed_fence);
  

•                 ret = -ETIMEDOUT;
  

•         } else if (ret != -ERESTARTSYS) {
  

•                 ret = 0;
  

•         }
  

• }
  

• return ret;
  

-}

• /* called from workqueue */ void msm_update_fence(struct msm_fence_context *fctx, uint32_t fence) { spin_lock(&fctx->spinlock); fctx->completed_fence = max(fence, fctx->completed_fence); spin_unlock(&fctx->spinlock);

• wake_up_all(&fctx->event);
  

  }

  struct msm_fence {

diff --git a/drivers/gpu/drm/msm/msm_fence.h b/drivers/gpu/drm/msm/msm_fence.h index 6ab97062ff1a..4783db528bcc 100644 --- a/drivers/gpu/drm/msm/msm_fence.h +++ b/drivers/gpu/drm/msm/msm_fence.h @@ -49,7 +49,6 @@ struct msm_fence_context { */ volatile uint32_t *fenceptr;

• wait_queue_head_t event;
  spinlock_t spinlock;
  

  };

@@ -57,8 +56,6 @@ struct msm_fence_context * msm_fence_context_alloc(struct drm_device *dev, volatile uint32_t *fenceptr, const char *name); void msm_fence_context_free(struct msm_fence_context *fctx);

-int msm_wait_fence(struct msm_fence_context *fctx, uint32_t fence,

•         ktime_t *timeout, bool interruptible);
  

  void msm_update_fence(struct msm_fence_context *fctx, uint32_t fence);

  struct dma_fence * msm_fence_alloc(struct msm_fence_context *fctx);

diff --git a/drivers/gpu/drm/msm/msm_gem.h b/drivers/gpu/drm/msm/msm_gem.h index da3af702a6c8..e0579abda5b9 100644 --- a/drivers/gpu/drm/msm/msm_gem.h +++ b/drivers/gpu/drm/msm/msm_gem.h @@ -320,6 +320,7 @@ struct msm_gem_submit { struct ww_acquire_ctx ticket; uint32_t seqno; /* Sequence number of the submit on the ring */ struct dma_fence *fence;

• int fence_id;       /* key into queue->fence_idr */
  struct msm_gpu_submitqueue *queue;
  struct pid *pid;    /* submitting process */
  bool fault_dumped;  /* Limit devcoredump dumping to one per submit */
  

diff --git a/drivers/gpu/drm/msm/msm_gem_submit.c b/drivers/gpu/drm/msm/msm_gem_submit.c index 4f02fa3c78f9..f6f595aae2c5 100644 --- a/drivers/gpu/drm/msm/msm_gem_submit.c +++ b/drivers/gpu/drm/msm/msm_gem_submit.c @@ -68,7 +68,14 @@ void __msm_gem_submit_destroy(struct kref *kref) container_of(kref, struct msm_gem_submit, ref); unsigned i;

• if (submit->fence_id) {
  

•         mutex_lock(&submit->queue->lock);
  

•         idr_remove(&submit->queue->fence_idr, submit->fence_id);
  

•         mutex_unlock(&submit->queue->lock);
  

• }
  

• dma_fence_put(submit->fence);
  

• put_pid(submit->pid);
  msm_submitqueue_put(submit->queue);
  
  

@@ -872,6 +879,20 @@ int msm_ioctl_gem_submit(struct drm_device *dev, void *data, goto out; }

• /*
  

•  * Allocate an id which can be used by WAIT_FENCE ioctl to map back
  

•  * to the underlying fence.
  

•  */
  

• mutex_lock(&queue->lock);
  

• submit->fence_id = idr_alloc_cyclic(&queue->fence_idr,
  

•                 submit->fence, 0, INT_MAX, GFP_KERNEL);
  

• mutex_unlock(&queue->lock);
  

• if (submit->fence_id < 0) {
  

•         ret = submit->fence_id = 0;
  

•         submit->fence_id = 0;
  

•         goto out;
  

• }
  

• if (args->flags & MSM_SUBMIT_FENCE_FD_OUT) {
          struct sync_file *sync_file = sync_file_create(submit->fence);
          if (!sync_file) {
  

@@ -886,7 +907,7 @@ int msm_ioctl_gem_submit(struct drm_device *dev, void *data,

  msm_gpu_submit(gpu, submit);

• args->fence = submit->fence->seqno;
  

• args->fence = submit->fence_id;
  
  msm_reset_syncobjs(syncobjs_to_reset, args->nr_in_syncobjs);
  msm_process_post_deps(post_deps, args->nr_out_syncobjs,
  

diff --git a/drivers/gpu/drm/msm/msm_gpu.h b/drivers/gpu/drm/msm/msm_gpu.h index 96efcb31e502..579627252540 100644 --- a/drivers/gpu/drm/msm/msm_gpu.h +++ b/drivers/gpu/drm/msm/msm_gpu.h @@ -263,6 +263,9 @@ struct msm_gpu_perfcntr {

•         which set of pgtables do submits jobs associated with the
  

•         submitqueue use)
  

• @node: node in the context's list of submitqueues

• • @fence_idr: maps fence-id to dma_fence for userspace visible fence

• •         seqno, protected by submitqueue lock
    

• • @lock: submitqueue lock
  • @ref: reference count
  */ struct msm_gpu_submitqueue {

@@ -272,6 +275,8 @@ struct msm_gpu_submitqueue { int faults; struct msm_file_private *ctx; struct list_head node;

• struct idr fence_idr;
  

• struct mutex lock;
  struct kref ref;
  

  };

diff --git a/drivers/gpu/drm/msm/msm_submitqueue.c b/drivers/gpu/drm/msm/msm_submitqueue.c index 9e9fec61d629..66f8d0fb38b0 100644 --- a/drivers/gpu/drm/msm/msm_submitqueue.c +++ b/drivers/gpu/drm/msm/msm_submitqueue.c @@ -12,6 +12,8 @@ void msm_submitqueue_destroy(struct kref *kref) struct msm_gpu_submitqueue *queue = container_of(kref, struct msm_gpu_submitqueue, ref);

• idr_destroy(&queue->fence_idr);
  

• msm_file_private_put(queue->ctx);
  
  kfree(queue);
  

@@ -89,6 +91,9 @@ int msm_submitqueue_create(struct drm_device *drm, struct msm_file_private *ctx, if (id) *id = queue->id;

• idr_init(&queue->fence_idr);
  

• mutex_init(&queue->lock);
  

• list_add_tail(&queue->node, &ctx->submitqueues);
  
  write_unlock(&ctx->queuelock);