Re: [PATCH v3 2/2] drm/xe: Use dma-fence array for media GT TLB invalidations in PT code

[Christian König <christian.koenig@xxxxxxx>]

Am 23.08.24 um 06:54 schrieb Matthew Brost:
> Using a chain fence is problematic as these cannot be installed in
> timeout drm sync objects. Use a dma-fence-array instead at the cost of
> an extra failure point.

Mhm, IIRC we converted chain objects into dma-fence-arrays while 
installing them into a timeline.

Doesn't that work any more?

Regards,
Christian.

> Also fixup reserve fence count to include media GT invalidation fence.
>
> v2:
>   - Fix reserve fence count (Casey Bowman)
> v3:
>   - Prealloc dma fence array (CI)
>
> Fixes: 40520283e0fd ("drm/xe: Invalidate media_gt TLBs in PT code")
> Signed-off-by: Matthew Brost <matthew.brost@xxxxxxxxx>
> ---
>   drivers/gpu/drm/xe/xe_pt.c | 34 ++++++++++++++++++++++++----------
>   1 file changed, 24 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/gpu/drm/xe/xe_pt.c b/drivers/gpu/drm/xe/xe_pt.c
> index 6c6714af3d5d..2e35444a85b0 100644
> --- a/drivers/gpu/drm/xe/xe_pt.c
> +++ b/drivers/gpu/drm/xe/xe_pt.c
> @@ -3,7 +3,7 @@
>    * Copyright © 2022 Intel Corporation
>    */
>   
> -#include <linux/dma-fence-chain.h>
> +#include <linux/dma-fence-array.h>
>   
>   #include "xe_pt.h"
>   
> @@ -1629,9 +1629,11 @@ xe_pt_update_ops_rfence_interval(struct xe_vm_pgtable_update_ops *pt_update_ops,
>   
>   static int vma_reserve_fences(struct xe_device *xe, struct xe_vma *vma)
>   {
> +	int shift = xe_device_get_root_tile(xe)->media_gt ? 1 : 0;
> +
>   	if (!xe_vma_has_no_bo(vma) && !xe_vma_bo(vma)->vm)
>   		return dma_resv_reserve_fences(xe_vma_bo(vma)->ttm.base.resv,
> -					       xe->info.tile_count);
> +					       xe->info.tile_count << shift);
>   
>   	return 0;
>   }
> @@ -1818,6 +1820,7 @@ int xe_pt_update_ops_prepare(struct xe_tile *tile, struct xe_vma_ops *vops)
>   	struct xe_vm_pgtable_update_ops *pt_update_ops =
>   		&vops->pt_update_ops[tile->id];
>   	struct xe_vma_op *op;
> +	int shift = tile->media_gt ? 1 : 0;
>   	int err;
>   
>   	lockdep_assert_held(&vops->vm->lock);
> @@ -1826,7 +1829,7 @@ int xe_pt_update_ops_prepare(struct xe_tile *tile, struct xe_vma_ops *vops)
>   	xe_pt_update_ops_init(pt_update_ops);
>   
>   	err = dma_resv_reserve_fences(xe_vm_resv(vops->vm),
> -				      tile_to_xe(tile)->info.tile_count);
> +				      tile_to_xe(tile)->info.tile_count << shift);
>   	if (err)
>   		return err;
>   
> @@ -1983,7 +1986,8 @@ xe_pt_update_ops_run(struct xe_tile *tile, struct xe_vma_ops *vops)
>   		&vops->pt_update_ops[tile->id];
>   	struct dma_fence *fence;
>   	struct invalidation_fence *ifence = NULL, *mfence = NULL;
> -	struct dma_fence_chain *chain_fence = NULL;
> +	struct dma_fence **fences = NULL;
> +	struct dma_fence_array *cf = NULL;
>   	struct xe_range_fence *rfence;
>   	struct xe_vma_op *op;
>   	int err = 0, i;
> @@ -2022,8 +2026,13 @@ xe_pt_update_ops_run(struct xe_tile *tile, struct xe_vma_ops *vops)
>   				err = -ENOMEM;
>   				goto free_ifence;
>   			}
> -			chain_fence = dma_fence_chain_alloc();
> -			if (!chain_fence) {
> +			fences = kmalloc_array(2, sizeof(*fences), GFP_KERNEL);
> +			if (!fences) {
> +				err = -ENOMEM;
> +				goto free_ifence;
> +			}
> +			cf = dma_fence_array_alloc(2);
> +			if (!cf) {
>   				err = -ENOMEM;
>   				goto free_ifence;
>   			}
> @@ -2068,9 +2077,13 @@ xe_pt_update_ops_run(struct xe_tile *tile, struct xe_vma_ops *vops)
>   			invalidation_fence_init(tile->media_gt, mfence, fence,
>   						pt_update_ops->start,
>   						pt_update_ops->last, vm->usm.asid);
> -			dma_fence_chain_init(chain_fence, &ifence->base.base,
> -					     &mfence->base.base, 0);
> -			fence = &chain_fence->base;
> +			fences[0] = &ifence->base.base;
> +			fences[1] = &mfence->base.base;
> +			dma_fence_array_arm(cf, 2, fences,
> +					    vm->composite_fence_ctx,
> +					    vm->composite_fence_seqno++,
> +					    false);
> +			fence = &cf->base;
>   		} else {
>   			fence = &ifence->base.base;
>   		}
> @@ -2108,7 +2121,8 @@ xe_pt_update_ops_run(struct xe_tile *tile, struct xe_vma_ops *vops)
>   free_rfence:
>   	kfree(rfence);
>   free_ifence:
> -	dma_fence_chain_free(chain_fence);
> +	kfree(cf);
> +	kfree(fences);
>   	kfree(mfence);
>   	kfree(ifence);
>   kill_vm_tile1: