target-arm: Implement asidx_from_attrs

Implement the asidx_from_attrs CPU method to return the
Secure or NonSecure address space as appropriate.

(The function is inline so we can use it directly in target-arm
code to be added in later patches.)

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Acked-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
diff --git a/target-arm/cpu.h b/target-arm/cpu.h
index 9108b5b..ee873b7 100644
--- a/target-arm/cpu.h
+++ b/target-arm/cpu.h
@@ -1997,4 +1997,12 @@
     QEMU_PSCI_CONDUIT_HVC = 2,
 };
 
+#ifndef CONFIG_USER_ONLY
+/* Return the address space index to use for a memory access */
+static inline int arm_asidx_from_attrs(CPUState *cs, MemTxAttrs attrs)
+{
+    return attrs.secure ? ARMASIdx_S : ARMASIdx_NS;
+}
+#endif
+
 #endif