[Bugfix] fixes the causal_conv1d_update kernel update non-speculative decoding cases (#24680)

Signed-off-by: Tao He <linzhu.ht@alibaba-inc.com>
Co-authored-by: Cyrus Leung <tlleungac@connect.ust.hk>

vllm/model_executor/layers/mamba/ops/causal_conv1d.py

@@ -720,15 +720,15 @@ def _causal_conv1d_update_kernel(
     # STEP 2: assume state_len > seqlen
     idx_tokens = tl.arange(0, NP2_STATELEN)  # [BLOCK_M]
 
-    # The conv_state updates works in a sliding window manner,
-    # at each forward pass, the tokens are shift by 1, so we
+    # With speculative decoding, the conv_state updates works in a sliding
+    # window manner, at each forward pass, the tokens are shift by 1, so we
     # load since idx_tokens + 1.
     conv_state_ptrs_source = (
         conv_state_ptr + (conv_state_batch_coord * stride_conv_state_seq) +
         conv_state_token_offset * stride_conv_state_tok +
         (idx_feats * stride_conv_state_dim)[None, :] +
-        ((idx_tokens + 1) * stride_conv_state_tok)[:, None]
-    )  # [BLOCK_M, BLOCK_N]
+        ((idx_tokens + (1 if IS_SPEC_DECODING else seqlen)) *
+         stride_conv_state_tok)[:, None])  # [BLOCK_M, BLOCK_N]
     mask = ((conv_state_batch_coord < num_cache_lines)
             & ((idx_tokens + seqlen) < state_len)[:, None]
             & (idx_feats < dim)[None, :])
@@ -924,7 +924,10 @@ def causal_conv1d_update(
     )
     stride_state_indices = conv_state_indices.stride(
         0) if conv_state_indices is not None else 0
-    state_len = width - 1 + (seqlen - 1)  # effective state_len needed
+    if num_accepted_tokens is not None:
+        state_len = width - 1 + (seqlen - 1)  # effective state_len needed
+    else:
+        state_len = width - 1
     np2_statelen = triton.next_power_of_2(state_len)
 
     def grid(META):