[V1][BugFix] Fix for mixed top_k batch (#14301)

Signed-off-by: Nick Hill <nhill@redhat.com>
Co-authored-by: Ye Cao <caoye.cao@alibaba-inc.com>

vllm/v1/worker/gpu_input_batch.py

@@ -264,9 +264,12 @@ class InputBatch:
         self.top_p_cpu[req_index] = sampling_params.top_p
         if sampling_params.top_p < 1:
             self.top_p_reqs.add(req_id)
-        self.top_k_cpu[req_index] = sampling_params.top_k
-        if sampling_params.top_k > 0:
+        top_k = sampling_params.top_k
+        if 0 < top_k < self.vocab_size:
             self.top_k_reqs.add(req_id)
+        else:
+            top_k = self.vocab_size
+        self.top_k_cpu[req_index] = top_k
         self.min_p_cpu[req_index] = sampling_params.min_p
         self.frequency_penalties_cpu[
             req_index] = sampling_params.frequency_penalty