Re: [PATCH] drm/xe: Use WRITE_ONCE for range->tile_invalidated update

[Maarten Lankhorst <maarten.lankhorst@linux.intel.com>]

Reviewed-by: Maarten Lankhrost <maarten.lankhorst@linux.intel.com>

On 2025-06-05 01:47, Matthew Brost wrote:
> Updating range->tile_invalidated should be done with WRITE_ONCE to pair
> with READ_ONCE in opportunistic checks.
> 
> Signed-off-by: Matthew Brost <matthew.brost@intel.com>
> ---
>  drivers/gpu/drm/xe/xe_svm.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_svm.c b/drivers/gpu/drm/xe/xe_svm.c
> index 83c63fd7b481..7df0bcea65fc 100644
> --- a/drivers/gpu/drm/xe/xe_svm.c
> +++ b/drivers/gpu/drm/xe/xe_svm.c
> @@ -141,7 +141,9 @@ xe_svm_range_notifier_event_begin(struct xe_vm *vm, struct drm_gpusvm_range *r,
>  	for_each_tile(tile, xe, id)
>  		if (xe_pt_zap_ptes_range(tile, vm, range)) {
>  			tile_mask |= BIT(id);
> -			range->tile_invalidated |= BIT(id);
> +			/* Pairs with READ_ONCE in xe_svm_range_is_valid */
> +			WRITE_ONCE(range->tile_invalidated,
> +				   range->tile_invalidated | BIT(id));
>  		}
>  
>  	return tile_mask;
> @@ -644,7 +646,8 @@ static bool xe_svm_range_is_valid(struct xe_svm_range *range,
>  {
>  	/*
>  	 * Advisory only check whether the range currently has a valid mapping,
> -	 * READ_ONCE pairs with WRITE_ONCE in xe_pt.c
> +	 * READ_ONCE pairs with WRITE_ONCE in xe_pt.c,
> +	 * xe_svm_range_notifier_event_begin
>  	 */
>  	return ((READ_ONCE(range->tile_present) &
>  		 ~READ_ONCE(range->tile_invalidated)) & BIT(tile->id)) &&