[Fix] Improve CPU backend compatibility for RISC-V (#25816)

Signed-off-by: lyd1992 <liuyudong@iscas.ac.cn>
Signed-off-by: ihb2032 <1355790728@qq.com>

vllm/engine/arg_utils.py

@@ -1160,11 +1160,12 @@ class EngineArgs:
 
         # Set default arguments for V1 Engine.
         self._set_default_args(usage_context, model_config)
-        # Disable chunked prefill for POWER (ppc64le)/ARM/s390x CPUs in V1
+        # Disable chunked prefill for POWER (ppc64le)/ARM/s390x/RISCV CPUs in V1
         if current_platform.is_cpu() and current_platform.get_cpu_architecture(
-        ) in (CpuArchEnum.POWERPC, CpuArchEnum.S390X, CpuArchEnum.ARM):
-            logger.info("Chunked prefill is not supported for ARM and POWER "
-                        "and S390X CPUs; "
+        ) in (CpuArchEnum.POWERPC, CpuArchEnum.S390X, CpuArchEnum.ARM,
+              CpuArchEnum.RISCV):
+            logger.info("Chunked prefill is not supported for ARM and POWER, "
+                        "S390X and RISC-V CPUs; "
                         "disabling it for V1 backend.")
             self.enable_chunked_prefill = False
         assert self.enable_chunked_prefill is not None