target/arm: Add el_is_in_host

This (newish) ARM pseudocode function is easier to work with
than open-coded tests for HCR_E2H etc.  Use of the function
will be staged into the code base in parts.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20220607203306.657998-6-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

target/arm/helper.c

@@ -5282,6 +5282,34 @@ uint64_t arm_hcr_el2_eff(CPUARMState *env)
     return ret;
 }
 
+/*
+ * Corresponds to ARM pseudocode function ELIsInHost().
+ */
+bool el_is_in_host(CPUARMState *env, int el)
+{
+    uint64_t mask;
+
+    /*
+     * Since we only care about E2H and TGE, we can skip arm_hcr_el2_eff().
+     * Perform the simplest bit tests first, and validate EL2 afterward.
+     */
+    if (el & 1) {
+        return false; /* EL1 or EL3 */
+    }
+
+    /*
+     * Note that hcr_write() checks isar_feature_aa64_vh(),
+     * aka HaveVirtHostExt(), in allowing HCR_E2H to be set.
+     */
+    mask = el ? HCR_E2H : HCR_E2H | HCR_TGE;
+    if ((env->cp15.hcr_el2 & mask) != mask) {
+        return false;
+    }
+
+    /* TGE and/or E2H set: double check those bits are currently legal. */
+    return arm_is_el2_enabled(env) && arm_el_is_aa64(env, 2);
+}
+
 static void hcrx_write(CPUARMState *env, const ARMCPRegInfo *ri,
                        uint64_t value)
 {

target/arm/internals.h

@@ -1347,6 +1347,8 @@ static inline void define_cortex_a72_a57_a53_cp_reginfo(ARMCPU *cpu) { }
 void define_cortex_a72_a57_a53_cp_reginfo(ARMCPU *cpu);
 #endif
 
+bool el_is_in_host(CPUARMState *env, int el);
+
 void aa32_max_features(ARMCPU *cpu);
 
 #endif