[CUTE][SM100] Fix backward gqa on sm100 post mask-mod semantic change

stack-info: PR: #2146, branch: drisspg/stack/11

Author: drisspg

tests/cute/test_mask_mod.py

@@ -95,7 +95,7 @@ def compute_reference_flex_attn(tensors, mask_mod_flex, block_size: tuple[int, i
         device=q.device,
         **block_mask_kwargs,
     )
-    out_ref = flex_attention(q, k, v, block_mask=block_mask, scale=scale)
+    out_ref = flex_attention(q, k, v, block_mask=block_mask, scale=scale, enable_gqa=True)
     return out_ref.transpose(1, 2).contiguous()
 
 
@@ -809,7 +809,7 @@ def run_flex_reference_bwd(q, k, v, block_mask, grad_out, dtype=None):
 
     # Use flex_attention directly without torch.compile for backward tests
     # torch.compile can hang on certain mask patterns (e.g., mini_causal with float32)
-    out_ref = flex_attention(q_ref, k_ref, v_ref, block_mask=block_mask)
+    out_ref = flex_attention(q_ref, k_ref, v_ref, block_mask=block_mask, enable_gqa=True)
     dq_ref, dk_ref, dv_ref = torch.autograd.grad(out_ref, (q_ref, k_ref, v_ref), grad_out_ref)
 
     # Transpose back to BSHD