Commit b14b8c5f authored by Rob Clark's avatar Rob Clark
Browse files

drm/msm: Decouple vma tracking from obj lock 



We need to use the inuse count to track that a BO is pinned until
we have the hw_fence.  But we want to remove the obj lock from the
job_run() path as this could deadlock against reclaim/shrinker
(because it is blocking the hw_fence from eventually being signaled).
So split that tracking out into a per-vma lock with narrower scope.

Signed-off-by: default avatarRob Clark <robdclark@chromium.org>
Patchwork: https://patchwork.freedesktop.org/patch/527839/
Link: https://lore.kernel.org/r/20230320144356.803762-5-robdclark@gmail.com
parent fc2f0756

drivers/gpu/drm/msm/msm_gem.h

+1 −0
Original line number Diff line number Diff line
@@ -59,6 +59,7 @@ struct msm_fence_context; 


struct msm_gem_vma {

	struct drm_mm_node node;

	spinlock_t lock;

	uint64_t iova;

	struct msm_gem_address_space *aspace;

	struct list_head list;    /* node in msm_gem_object::vmas */

drivers/gpu/drm/msm/msm_gem_vma.c

+38 −6
Original line number Diff line number Diff line
@@ -40,19 +40,28 @@ msm_gem_address_space_get(struct msm_gem_address_space *aspace) 


bool msm_gem_vma_inuse(struct msm_gem_vma *vma)

{

	bool ret = true;



	spin_lock(&vma->lock);



	if (vma->inuse > 0)

		return true;

		goto out;



	while (vma->fence_mask) {

		unsigned idx = ffs(vma->fence_mask) - 1;



		if (!msm_fence_completed(vma->fctx[idx], vma->fence[idx]))

			return true;

			goto out;



		vma->fence_mask &= ~BIT(idx);

	}



	return false;

	ret = false;



out:

	spin_unlock(&vma->lock);



	return ret;

}



/* Actually unmap memory for the vma */
@@ -73,8 +82,7 @@ void msm_gem_vma_purge(struct msm_gem_vma *vma) 
	vma->mapped = false;

}



/* Remove reference counts for the mapping */

void msm_gem_vma_unpin(struct msm_gem_vma *vma)

static void vma_unpin_locked(struct msm_gem_vma *vma)

{

	if (GEM_WARN_ON(!vma->inuse))

		return;
@@ -82,13 +90,23 @@ void msm_gem_vma_unpin(struct msm_gem_vma *vma) 
		vma->inuse--;

}



/* Remove reference counts for the mapping */

void msm_gem_vma_unpin(struct msm_gem_vma *vma)

{

	spin_lock(&vma->lock);

	vma_unpin_locked(vma);

	spin_unlock(&vma->lock);

}



/* Replace pin reference with fence: */

void msm_gem_vma_unpin_fenced(struct msm_gem_vma *vma, struct msm_fence_context *fctx)

{

	spin_lock(&vma->lock);

	vma->fctx[fctx->index] = fctx;

	vma->fence[fctx->index] = fctx->last_fence;

	vma->fence_mask |= BIT(fctx->index);

	msm_gem_vma_unpin(vma);

	vma_unpin_locked(vma);

	spin_unlock(&vma->lock);

}



/* Map and pin vma: */
@@ -103,7 +121,9 @@ msm_gem_vma_map(struct msm_gem_vma *vma, int prot, 
		return -EINVAL;



	/* Increase the usage counter */

	spin_lock(&vma->lock);

	vma->inuse++;

	spin_unlock(&vma->lock);



	if (vma->mapped)

		return 0;
@@ -113,11 +133,22 @@ msm_gem_vma_map(struct msm_gem_vma *vma, int prot, 
	if (!aspace)

		return 0;



	/*

	 * NOTE: iommu/io-pgtable can allocate pages, so we cannot hold

	 * a lock across map/unmap which is also used in the job_run()

	 * path, as this can cause deadlock in job_run() vs shrinker/

	 * reclaim.

	 *

	 * Revisit this if we can come up with a scheme to pre-alloc pages

	 * for the pgtable in map/unmap ops.

	 */

	ret = aspace->mmu->funcs->map(aspace->mmu, vma->iova, sgt, size, prot);



	if (ret) {

		vma->mapped = false;

		spin_lock(&vma->lock);

		vma->inuse--;

		spin_unlock(&vma->lock);

	}



	return ret;
@@ -148,6 +179,7 @@ struct msm_gem_vma *msm_gem_vma_new(struct msm_gem_address_space *aspace) 
	if (!vma)

		return NULL;



	spin_lock_init(&vma->lock);

	vma->aspace = aspace;



	return vma;

drivers/gpu/drm/msm/msm_ringbuffer.c

+1 −1
Original line number Diff line number Diff line
@@ -23,8 +23,8 @@ static struct dma_fence *msm_job_run(struct drm_sched_job *job) 
	for (i = 0; i < submit->nr_bos; i++) {

		struct drm_gem_object *obj = &submit->bos[i].obj->base;



		msm_gem_lock(obj);

		msm_gem_vma_unpin_fenced(submit->bos[i].vma, fctx);

		msm_gem_lock(obj);

		msm_gem_unpin_locked(obj);

		msm_gem_unlock(obj);

		submit->bos[i].flags &= ~(BO_VMA_PINNED | BO_OBJ_PINNED);