[PATCH i-g-t] lib/xe: Fix allocation for vram_size and visible_vram_size based on max_gt

[Kamil Konieczny]

Hi Gustavo,
On 2025-07-10 at 19:12:27 -0300, Gustavo Sousa wrote:
> The current allocation for vram_size and visible_vram_size has two
> issues:
> 
> * The expression (max_gt = ffsll(xe_dev->gt_mask) - 1) gives us the
>   zero-based index of the first bit set in the mask, which does not give
>   us the maximum GT ID, but the minimum.
> 
> * Since max_gt is zero-based, even if its value was right, we would
>   still be allocating not enough entries for the array.
> 
> Fix that by calculating max_gt in the same way that xe_dev_max_gt() does
> and using (max_gt + 1) as argument to calloc().
> 
> Cc: Matt Roper <matthew.d.roper at intel.com>
> Cc: Zbigniew Kempczyński <zbigniew.kempczynski at intel.com>
> Fixes: 3a39a6e51b18 ("lib/xe: Populate vram_size[] and visible_vram_size[] by GT ID")
> Signed-off-by: Gustavo Sousa <gustavo.sousa at intel.com>
> ---
>  lib/xe/xe_query.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/lib/xe/xe_query.c b/lib/xe/xe_query.c
> index 3d628cb3fe59ddc390684941452ca04fd735b212..c0dba018244e8a47c8f1b305cf43ec3d4ffdc575 100644
> --- a/lib/xe/xe_query.c
> +++ b/lib/xe/xe_query.c
> @@ -361,9 +361,9 @@ struct xe_device *xe_device_get(int fd)
>  	 * vram_size[] and visible_vram_size[] are indexed by uapi ID; ensure
>  	 * the allocation is large enough to hold the highest GT ID
>  	 */
> -	max_gt = ffsll(xe_dev->gt_mask) - 1;
> -	xe_dev->vram_size = calloc(max_gt, sizeof(*xe_dev->vram_size));
> -	xe_dev->visible_vram_size = calloc(max_gt, sizeof(*xe_dev->visible_vram_size));
> +	max_gt = igt_fls(xe_dev->gt_mask) - 1;
> +	xe_dev->vram_size = calloc(max_gt + 1, sizeof(*xe_dev->vram_size));
> +	xe_dev->visible_vram_size = calloc(max_gt + 1, sizeof(*xe_dev->visible_vram_size));

It could also just use value from below for loop?
For example:
	max_gt = xe_dev->gt_list->num_gt - 1;

If yes this could be someting for future change.

Reviewed-by: Kamil Konieczny <kamil.konieczny at linux.intel.com>

>  
>  	for (int idx = 0; idx < xe_dev->gt_list->num_gt; idx++) {
>  		struct drm_xe_gt *gt = &xe_dev->gt_list->gt_list[idx];
> 
> ---
> base-commit: eacde5c2acc37c1570e27b68b8b6c39d8b61fb32
> change-id: 20250710-fix-allocation-of-vram_size-and-visible_vram_size-f194f0e55610
> 
> Best regards,
> -- 
> Gustavo Sousa <gustavo.sousa at intel.com>
>