Re: [PATCH v2 7/7] drm/xe/pt: unify xe_pt_svm_pre_commit with userptr

[Matthew Brost <matthew.brost@intel.com>]

On Fri, Mar 28, 2025 at 06:10:36PM +0000, Matthew Auld wrote:
> We now use the same notifier lock for SVM and userptr, with that we can
> combine xe_pt_userptr_pre_commit and xe_pt_svm_pre_commit.
> 
> Suggested-by: Matthew Brost <matthew.brost@intel.com>
> Signed-off-by: Matthew Auld <matthew.auld@intel.com>
> Cc: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
> Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> ---
>  drivers/gpu/drm/xe/xe_pt.c | 95 +++++++++++++-------------------------
>  1 file changed, 33 insertions(+), 62 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_pt.c b/drivers/gpu/drm/xe/xe_pt.c
> index b097c91e2e02..947b82aa19a6 100644
> --- a/drivers/gpu/drm/xe/xe_pt.c
> +++ b/drivers/gpu/drm/xe/xe_pt.c
> @@ -1396,7 +1396,7 @@ static int op_check_userptr(struct xe_vm *vm, struct xe_vma_op *op,
>  	return err;
>  }
>  
> -static int xe_pt_userptr_pre_commit(struct xe_migrate_pt_update *pt_update)
> +static int xe_pt_svm_userptr_pre_commit(struct xe_migrate_pt_update *pt_update)
>  {
>  	struct xe_vm *vm = pt_update->vops->vm;
>  	struct xe_vma_ops *vops = pt_update->vops;
> @@ -1409,55 +1409,40 @@ static int xe_pt_userptr_pre_commit(struct xe_migrate_pt_update *pt_update)
>  	if (err)
>  		return err;
>  
> -	down_read(&vm->svm.gpusvm.notifier_lock);
> +	drm_gpusvm_notifier_lock(&vm->svm.gpusvm);
>  
>  	list_for_each_entry(op, &vops->list, link) {
> -		err = op_check_userptr(vm, op, pt_update_ops);
> -		if (err) {
> -			up_read(&vm->svm.gpusvm.notifier_lock);
> -			break;
> +		if (pt_update_ops->needs_svm_lock) {
> +#if IS_ENABLED(CONFIG_DRM_XE_GPUSVM)
> +			struct xe_svm_range *range = op->map_range.range;
> +
> +			if (op->subop == XE_VMA_SUBOP_UNMAP_RANGE)
> +				continue;
> +
> +			xe_svm_range_debug(range, "PRE-COMMIT");
> +
> +			xe_assert(vm->xe,
> +				  xe_vma_is_cpu_addr_mirror(op->map_range.vma));
> +			xe_assert(vm->xe, op->subop == XE_VMA_SUBOP_MAP_RANGE);
> +
> +			if (!xe_svm_range_pages_valid(range)) {
> +				xe_svm_range_debug(range, "PRE-COMMIT - RETRY");
> +				drm_gpusvm_notifier_unlock(&vm->svm.gpusvm);
> +				return -EAGAIN;
> +			}
> +#endif
> +		} else {
> +			err = op_check_userptr(vm, op, pt_update_ops);

I think it would be better to combine needs_svm_lock into a single
variable, rename op_check_userptr to op_check_svm_userptr, and then add
the code in the above if statement to op_check_svm_userptr. Yes, the way
have it coded now works but when Himal's code for SVM prefetch lands a
VM operation list could have both userptr binds and binds SVM within
single list. Changing it per my suggestion should make that work too.

Matt

> +			if (err) {
> +				drm_gpusvm_notifier_unlock(&vm->svm.gpusvm);
> +				break;
> +			}
>  		}
>  	}
>  
>  	return err;
>  }
>  
> -#if IS_ENABLED(CONFIG_DRM_XE_GPUSVM)
> -static int xe_pt_svm_pre_commit(struct xe_migrate_pt_update *pt_update)
> -{
> -	struct xe_vm *vm = pt_update->vops->vm;
> -	struct xe_vma_ops *vops = pt_update->vops;
> -	struct xe_vma_op *op;
> -	int err;
> -
> -	err = xe_pt_pre_commit(pt_update);
> -	if (err)
> -		return err;
> -
> -	xe_svm_notifier_lock(vm);
> -
> -	list_for_each_entry(op, &vops->list, link) {
> -		struct xe_svm_range *range = op->map_range.range;
> -
> -		if (op->subop == XE_VMA_SUBOP_UNMAP_RANGE)
> -			continue;
> -
> -		xe_svm_range_debug(range, "PRE-COMMIT");
> -
> -		xe_assert(vm->xe, xe_vma_is_cpu_addr_mirror(op->map_range.vma));
> -		xe_assert(vm->xe, op->subop == XE_VMA_SUBOP_MAP_RANGE);
> -
> -		if (!xe_svm_range_pages_valid(range)) {
> -			xe_svm_range_debug(range, "PRE-COMMIT - RETRY");
> -			xe_svm_notifier_unlock(vm);
> -			return -EAGAIN;
> -		}
> -	}
> -
> -	return 0;
> -}
> -#endif
> -
>  struct invalidation_fence {
>  	struct xe_gt_tlb_invalidation_fence base;
>  	struct xe_gt *gt;
> @@ -2255,22 +2240,12 @@ static const struct xe_migrate_pt_update_ops migrate_ops = {
>  	.pre_commit = xe_pt_pre_commit,
>  };
>  
> -static const struct xe_migrate_pt_update_ops userptr_migrate_ops = {
> +static const struct xe_migrate_pt_update_ops svm_userptr_migrate_ops = {
>  	.populate = xe_vm_populate_pgtable,
>  	.clear = xe_migrate_clear_pgtable_callback,
> -	.pre_commit = xe_pt_userptr_pre_commit,
> +	.pre_commit = xe_pt_svm_userptr_pre_commit,
>  };
>  
> -#if IS_ENABLED(CONFIG_DRM_XE_GPUSVM)
> -static const struct xe_migrate_pt_update_ops svm_migrate_ops = {
> -	.populate = xe_vm_populate_pgtable,
> -	.clear = xe_migrate_clear_pgtable_callback,
> -	.pre_commit = xe_pt_svm_pre_commit,
> -};
> -#else
> -static const struct xe_migrate_pt_update_ops svm_migrate_ops;
> -#endif
> -
>  /**
>   * xe_pt_update_ops_run() - Run PT update operations
>   * @tile: Tile of PT update operations
> @@ -2296,10 +2271,8 @@ xe_pt_update_ops_run(struct xe_tile *tile, struct xe_vma_ops *vops)
>  	struct xe_vma_op *op;
>  	int err = 0, i;
>  	struct xe_migrate_pt_update update = {
> -		.ops = pt_update_ops->needs_svm_lock ?
> -			&svm_migrate_ops :
> -			pt_update_ops->needs_userptr_lock ?
> -			&userptr_migrate_ops :
> +		.ops = pt_update_ops->needs_svm_lock || pt_update_ops->needs_userptr_lock ?
> +			&svm_userptr_migrate_ops :
>  			&migrate_ops,
>  		.vops = vops,
>  		.tile_id = tile->id,
> @@ -2419,10 +2392,8 @@ xe_pt_update_ops_run(struct xe_tile *tile, struct xe_vma_ops *vops)
>  				  &ifence->base.base, &mfence->base.base);
>  	}
>  
> -	if (pt_update_ops->needs_svm_lock)
> -		xe_svm_notifier_unlock(vm);
> -	if (pt_update_ops->needs_userptr_lock)
> -		up_read(&vm->svm.gpusvm.notifier_lock);
> +	if (pt_update_ops->needs_svm_lock || pt_update_ops->needs_userptr_lock)
> +		drm_gpusvm_notifier_unlock(&vm->svm.gpusvm);
>  
>  	return fence;
>  
> -- 
> 2.48.1
>