target-arm: powerctl: Enable HVC when starting CPUs to EL2

When QEMU provides the equivalent of the EL3 firmware, we
need to enable HVCs in scr_el3 when turning on CPUs that
target EL2.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
Message-id: 20181011021931.4249-10-edgar.iglesias@gmail.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

target/arm/arm-powerctl.c

@@ -103,6 +103,16 @@ static void arm_set_cpu_on_async_work(CPUState *target_cpu_state,
     } else {
         /* Processor is not in secure mode */
         target_cpu->env.cp15.scr_el3 |= SCR_NS;
+
+        /*
+         * If QEMU is providing the equivalent of EL3 firmware, then we need
+         * to make sure a CPU targeting EL2 comes out of reset with a
+         * functional HVC insn.
+         */
+        if (arm_feature(&target_cpu->env, ARM_FEATURE_EL3)
+            && info->target_el == 2) {
+            target_cpu->env.cp15.scr_el3 |= SCR_HCE;
+        }
     }
 
     /* We check if the started CPU is now at the correct level */