target/riscv: rvv-1.0: check MSTATUS_VS when accessing vector csr registers

If VS field is off, accessing vector csr registers should raise an
illegal-instruction exception.

Signed-off-by: Frank Chang <frank.chang@sifive.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-Id: <20211210075704.23951-12-frank.chang@sifive.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

target/riscv/csr.c

@@ -48,6 +48,11 @@ static RISCVException fs(CPURISCVState *env, int csrno)
 static RISCVException vs(CPURISCVState *env, int csrno)
 {
     if (env->misa_ext & RVV) {
+#if !defined(CONFIG_USER_ONLY)
+        if (!env->debugger && !riscv_cpu_vector_enabled(env)) {
+            return RISCV_EXCP_ILLEGAL_INST;
+        }
+#endif
         return RISCV_EXCP_NONE;
     }
     return RISCV_EXCP_ILLEGAL_INST;