arm: tcg: Adhere to SMCCC 1.3 section 5.2

The SMCCC 1.3 spec section 5.2 says

  The Unknown SMC Function Identifier is a sign-extended value of (-1)
  that is returned in the R0, W0 or X0 registers. An implementation must
  return this error code when it receives:

    * An SMC or HVC call with an unknown Function Identifier
    * An SMC or HVC call for a removed Function Identifier
    * An SMC64/HVC64 call from AArch32 state

To comply with these statements, let's always return -1 when we encounter
an unknown HVC or SMC call.

[PMM:
 This is a reinstatement of commit 9fcd15b9, previously
 reverted in commit 4825eaae; we can do this now that we
 have arranged for all the affected board models to not enable the
 PSCI emulation if they are running guest code at EL3. This avoids
 the regressions that caused us to revert the change for 7.0.]

Signed-off-by: Alexander Graf <agraf@csgraf.de>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Niek Linnenbank <nieklinnenbank@gmail.com>
Tested-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
Tested-by: Cédric Le Goater <clg@kaod.org>
Tested-by: Niek Linnenbank <nieklinnenbank@gmail.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

target/arm/psci.c

@@ -27,15 +27,13 @@
 
 bool arm_is_psci_call(ARMCPU *cpu, int excp_type)
 {
-    /* Return true if the r0/x0 value indicates a PSCI call and
-     * the exception type matches the configured PSCI conduit. This is
-     * called before the SMC/HVC instruction is executed, to decide whether
-     * we should treat it as a PSCI call or with the architecturally
+    /*
+     * Return true if the exception type matches the configured PSCI conduit.
+     * This is called before the SMC/HVC instruction is executed, to decide
+     * whether we should treat it as a PSCI call or with the architecturally
      * defined behaviour for an SMC or HVC (which might be UNDEF or trap
      * to EL2 or to EL3).
      */
-    CPUARMState *env = &cpu->env;
-    uint64_t param = is_a64(env) ? env->xregs[0] : env->regs[0];
 
     switch (excp_type) {
     case EXCP_HVC:
@@ -52,27 +50,7 @@ bool arm_is_psci_call(ARMCPU *cpu, int excp_type)
         return false;
     }
 
-    switch (param) {
-    case QEMU_PSCI_0_2_FN_PSCI_VERSION:
-    case QEMU_PSCI_0_2_FN_MIGRATE_INFO_TYPE:
-    case QEMU_PSCI_0_2_FN_AFFINITY_INFO:
-    case QEMU_PSCI_0_2_FN64_AFFINITY_INFO:
-    case QEMU_PSCI_0_2_FN_SYSTEM_RESET:
-    case QEMU_PSCI_0_2_FN_SYSTEM_OFF:
-    case QEMU_PSCI_0_1_FN_CPU_ON:
-    case QEMU_PSCI_0_2_FN_CPU_ON:
-    case QEMU_PSCI_0_2_FN64_CPU_ON:
-    case QEMU_PSCI_0_1_FN_CPU_OFF:
-    case QEMU_PSCI_0_2_FN_CPU_OFF:
-    case QEMU_PSCI_0_1_FN_CPU_SUSPEND:
-    case QEMU_PSCI_0_2_FN_CPU_SUSPEND:
-    case QEMU_PSCI_0_2_FN64_CPU_SUSPEND:
-    case QEMU_PSCI_0_1_FN_MIGRATE:
-    case QEMU_PSCI_0_2_FN_MIGRATE:
-        return true;
-    default:
-        return false;
-    }
+    return true;
 }
 
 void arm_handle_psci_call(ARMCPU *cpu)
@@ -194,10 +172,9 @@ void arm_handle_psci_call(ARMCPU *cpu)
         break;
     case QEMU_PSCI_0_1_FN_MIGRATE:
     case QEMU_PSCI_0_2_FN_MIGRATE:
+    default:
         ret = QEMU_PSCI_RET_NOT_SUPPORTED;
         break;
-    default:
-        g_assert_not_reached();
     }
 
 err: