Re: [PATCH] drm/xe/vm: Use for_each_tlb_inval() to calculate invalidation fences

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

On Tue, Nov 18, 2025 at 12:14:40PM -0800, Matt Roper wrote:
> ops_execute() calculates the size of a fence array based on
> XE_MAX_GT_PER_TILE, while the code that actually fills in the fence
> array uses a for_each_tlb_inval() iterator.  This works out okay today
> since both approaches come up with the same number of invalidation
> fences (2: primary GT invalidation + media GT invalidation), but could
> be problematic in the future if there isn't a 1:1 relationship between
> TLBs needing invalidation and potential GTs on the tile.
> 
> Adjust the allocation code to use the same for_each_tlb_inval()
> counting logic as the code that fills the array to future-proof the
> code.
> 
> Signed-off-by: Matt Roper <matthew.d.roper@intel.com>

Reviewed-by: Matthew Brost <matthew.brost@intel.com>

> ---
>  drivers/gpu/drm/xe/xe_vm.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_vm.c b/drivers/gpu/drm/xe/xe_vm.c
> index 7cac646bdf1c..6794f38b9340 100644
> --- a/drivers/gpu/drm/xe/xe_vm.c
> +++ b/drivers/gpu/drm/xe/xe_vm.c
> @@ -3111,12 +3111,12 @@ static struct dma_fence *ops_execute(struct xe_vm *vm,
>  	if (number_tiles == 0)
>  		return ERR_PTR(-ENODATA);
>  
> -	if (vops->flags & XE_VMA_OPS_FLAG_SKIP_TLB_WAIT) {
> -		for_each_tile(tile, vm->xe, id)
> -			++n_fence;
> -	} else {
> -		for_each_tile(tile, vm->xe, id)
> -			n_fence += (1 + XE_MAX_GT_PER_TILE);
> +	for_each_tile(tile, vm->xe, id) {
> +		++n_fence;
> +
> +		if (!(vops->flags & XE_VMA_OPS_FLAG_SKIP_TLB_WAIT))
> +			for_each_tlb_inval(i)
> +				++n_fence;
>  	}
>  
>  	fences = kmalloc_array(n_fence, sizeof(*fences), GFP_KERNEL);
> -- 
> 2.51.1
>