[Bugfix][Kernel] Fix negative memory offset in GDN Triton kernel (#33326)

Signed-off-by: CarstyYou <186021327+CarstyYou@users.noreply.github.com>

vllm/model_executor/layers/fla/ops/fused_recurrent.py

@@ -106,13 +106,14 @@ def fused_recurrent_gated_delta_rule_fwd_kernel(
                 i_t = tl.load(num_accepted_tokens + i_n).to(tl.int64) - 1
             else:
                 i_t = 0
-            p_h0 = (
-                h0
-                + tl.load(ssm_state_indices + i_n * stride_indices_seq + i_t).to(
-                    tl.int64
-                )
-                * stride_init_state_token
+            # Load state index and check for PAD_SLOT_ID (-1)
+            state_idx = tl.load(ssm_state_indices + i_n * stride_indices_seq + i_t).to(
+                tl.int64
             )
+            # Skip if state index is invalid (PAD_SLOT_ID = -1)
+            if state_idx < 0:
+                return
+            p_h0 = h0 + state_idx * stride_init_state_token
         else:
             p_h0 = h0 + bos * HV * K * V
         p_h0 = p_h0 + i_hv * K * V + o_k[:, None] * V + o_v[None, :]
@@ -149,17 +150,19 @@ def fused_recurrent_gated_delta_rule_fwd_kernel(
 
         # keep the states for multi-query tokens
         if INPLACE_FINAL_STATE:
-            p_ht = (
-                ht
-                + tl.load(ssm_state_indices + i_n * stride_indices_seq + i_t).to(
-                    tl.int64
-                )
-                * stride_final_state_token
-            )
+            # Load state index and check for PAD_SLOT_ID (-1)
+            final_state_idx = tl.load(
+                ssm_state_indices + i_n * stride_indices_seq + i_t
+            ).to(tl.int64)
+            # Only store if state index is valid (not PAD_SLOT_ID)
+            if final_state_idx >= 0:
+                p_ht = ht + final_state_idx * stride_final_state_token
+                p_ht = p_ht + i_hv * K * V + o_k[:, None] * V + o_v[None, :]
+                tl.store(p_ht, b_h.to(p_ht.dtype.element_ty), mask=mask_h)
         else:
             p_ht = ht + (bos + i_t) * stride_final_state_token
-        p_ht = p_ht + i_hv * K * V + o_k[:, None] * V + o_v[None, :]
-        tl.store(p_ht, b_h.to(p_ht.dtype.element_ty), mask=mask_h)
+            p_ht = p_ht + i_hv * K * V + o_k[:, None] * V + o_v[None, :]
+            tl.store(p_ht, b_h.to(p_ht.dtype.element_ty), mask=mask_h)
 
         p_q += H * K
         p_k += H * K