Re: [PATCH] drm/xe: Keep walking on SVM eviction failure

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] Unconditionally masking `xe_svm_bo_evict()` errors as `-ENOSPC` hides fatal errors and triggers TTM error log spam.
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commit 8fcbc00a7aa0e3b2119f7df96129747882247423
Author: Matthew Brost <matthew.brost@intel.com>

drm/xe: Keep walking on SVM eviction failure

This commit adjusts the error handling in xe_bo_move() for SVM eviction
failures. It overwrites the return code from xe_svm_bo_evict() with -ENOSPC
to force TTM to continue walking the LRU list for eviction candidates.

> diff --git a/drivers/gpu/drm/xe/xe_bo.c b/drivers/gpu/drm/xe/xe_bo.c
> --- a/drivers/gpu/drm/xe/xe_bo.c
> +++ b/drivers/gpu/drm/xe/xe_bo.c
> @@ -1043,6 +1043,11 @@ static int xe_bo_move(struct ttm_buffer_object *ttm_bo, bool evict,
>  		} else {
>  			drm_dbg(&xe->drm, "Evict system allocator BO failed=%pe\n",
>  				ERR_PTR(ret));
> +			/*
> +			 * The semantic we want upon SVM eviction failure is
> +			 * keep walking for eviction, which is -ENOSPC.
> +			 */
> +			ret = -ENOSPC;

[Severity: Medium]
Does unconditionally overwriting the error with -ENOSPC hide fatal errors like
-ENOMEM?

When system memory is exhausted, xe_svm_bo_evict() can return -ENOMEM. By
masking this as -ENOSPC, it seems we might break proper error propagation to
higher layers, preventing expected OOM handling.

Furthermore, could this trigger a TTM error log spam loop? When returned to
TTM, -ENOSPC causes ttm_bo_evict() to log an unconditional
pr_err("Buffer eviction failed\n"). Since -ENOSPC is converted to -EBUSY in
ttm_bo_evict_cb(), it signals the LRU walker (ttm_lru_walk_for_evict()) to
skip the BO and continue walking. 

During genuine resource exhaustion, this might cause a fruitless iteration over
the entire LRU list, logging a pr_err() for every single buffer object. Even
benign SVM races might spam the kernel log with errors.

>  		}
>  
>  		goto out;

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Sashiko AI review · https://sashiko.dev/#/patchset/20260908184346.92332-1-matthew.brost@intel.com?part=1