Re: [PATCH v2] drm/xe/tests: Fix g2g_test_array indexing

[Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>]

On 1/15/2026 4:25 PM, Pallavi Mishra wrote:
> The G2G KUnit test allocates a compact N×N
> matrix sized by gt_count and verifies entries
> using dense indices: idx = (j * gt_count) + i
>
> The producer path currently computes idx using
> gt->info.id. However, gt->info.id values
> are not guaranteed to be contiguous.
> For example, with gt_count=2 and IDs {0,3},
> this formula produces indices beyond the
> allocated range, causing mismatches and
> potential out-of-bounds access.
>
> Update the producer to map each GT to a dense
> index in [0..gt_count-1] and compute:
>      idx = (tx_dense * gt_count) + rx_dense
>
> Additionally, introduce an event-based delay
> in g2g_test_in_order() to ensure ordering
> between sends.
>
> v2: Add single helper function (Daniele)
>
> Signed-off-by: Pallavi Mishra <pallavi.mishra@intel.com>
> ---
>   drivers/gpu/drm/xe/tests/xe_guc_g2g_test.c | 56 +++++++++++++++++++++-
>   1 file changed, 54 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/xe/tests/xe_guc_g2g_test.c b/drivers/gpu/drm/xe/tests/xe_guc_g2g_test.c
> index 3b213fcae916..ec18086b98d8 100644
> --- a/drivers/gpu/drm/xe/tests/xe_guc_g2g_test.c
> +++ b/drivers/gpu/drm/xe/tests/xe_guc_g2g_test.c
> @@ -48,6 +48,38 @@ struct g2g_test_payload  {
>   	u32 seqno;
>   };
>   
> +static int slot_index_from_gts(struct xe_gt *tx_gt, struct xe_gt *rx_gt)
> +{
> +	struct xe_device *xe = gt_to_xe(tx_gt);
> +	int idx = 0, found = 0, id, tx_idx, rx_idx;
> +	struct xe_gt *gt;
> +	struct kunit *test = kunit_get_current_test();
> +
> +	for (id = 0; id < xe->info.tile_count * xe->info.max_gt_per_tile; id++) {
> +		gt = xe_device_get_gt(xe, id);
> +		if (!gt)
> +			continue;
> +		if (gt == tx_gt) {
> +			tx_idx = idx;
> +			found++;
> +		}
> +		if (gt == rx_gt) {
> +			rx_idx = idx;
> +			found++;
> +		}
> +
> +		if (found == 2)
> +			break;
> +
> +		idx++;
> +	}
> +
> +	if (found != 2)
> +		KUNIT_FAIL(test, "GT index not found");
> +
> +	return (tx_idx * xe->info.gt_count) + rx_idx;
> +}
> +
>   static void g2g_test_send(struct kunit *test, struct xe_guc *guc,
>   			  u32 far_tile, u32 far_dev,
>   			  struct g2g_test_payload *payload)
> @@ -163,7 +195,7 @@ int xe_guc_g2g_test_notification(struct xe_guc *guc, u32 *msg, u32 len)
>   		goto done;
>   	}
>   
> -	idx = (tx_gt->info.id * xe->info.gt_count) + rx_gt->info.id;
> +	idx = slot_index_from_gts(tx_gt, rx_gt);
>   
>   	if (xe->g2g_test_array[idx] != payload->seqno - 1) {
>   		xe_gt_err(rx_gt, "G2G: Seqno mismatch %d vs %d for %d:%d -> %d:%d!\n",
> @@ -180,13 +212,17 @@ int xe_guc_g2g_test_notification(struct xe_guc *guc, u32 *msg, u32 len)
>   	return ret;
>   }
>   
> +#define G2G_WAIT_TIMEOUT_MS 100
> +#define G2G_WAIT_POLL_MS 1
> +
>   /*
>    * Send the given seqno from all GuCs to all other GuCs in tile/GT order
>    */
>   static void g2g_test_in_order(struct kunit *test, struct xe_device *xe, u32 seqno)
>   {
>   	struct xe_gt *near_gt, *far_gt;
> -	int i, j;
> +	int i, j, waited;
> +	u32 idx;
>   
>   	for_each_gt(near_gt, xe, i) {
>   		u32 near_tile = gt_to_tile(near_gt)->id;
> @@ -205,6 +241,22 @@ static void g2g_test_in_order(struct kunit *test, struct xe_device *xe, u32 seqn
>   			payload.rx_dev = far_dev;
>   			payload.rx_tile = far_tile;
>   			payload.seqno = seqno;
> +
> +			/* Calculate idx for event-based wait */
> +			idx = slot_index_from_gts(near_gt, far_gt);
> +			waited = 0;
> +
> +			/* Wait for previous seqno to be acknowledged before sending */
> +			while (xe->g2g_test_array[idx] != (seqno - 1)) {
> +				msleep(G2G_WAIT_POLL_MS);
> +				waited += G2G_WAIT_POLL_MS;
> +				if (waited >= G2G_WAIT_TIMEOUT_MS) {
> +					kunit_info(test, "Timeout waiting! tx gt: %d, rx gt: %d\n",
> +						   near_gt->info.id, far_gt->info.id);

Sorry I missed this on the previous rev, but shouldn't this be a 
failure? If we don't get one of the previous messages then something has 
gone wrong.
The patch looks good to me apart from this.

Daniele

> +					break;
> +				}
> +			}
> +
>   			g2g_test_send(test, &near_gt->uc.guc, far_tile, far_dev, &payload);
>   		}
>   	}