target-arm: Add utility function for checking AA32/64 state of an EL

There are various situations where we need to behave differently
depending on whether a given exception level is in AArch64 or
AArch32 state. The state of the current exception level is stored
in env->aarch64, but there's no equivalent guest-visible architected
state bits for the status of the exception levels "above" the
current one which may still affect execution. At the moment we
only support EL1 (ie no EL2 or EL3) and insist that AArch64
capable CPUs run with EL1 in AArch64 state, but these may change
in the future, so abstract out the "what state is this?" check
into a utility function which can be enhanced later if necessary.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 16 insertions, 0 deletions

diff --git a/target-arm/cpu.h b/target-arm/cpu.h
index 1f6f65d78..f53033392 100644
--- a/target-arm/cpu.h
+++ b/target-arm/cpu.h
@@ -633,6 +633,22 @@ static inline int arm_feature(CPUARMState *env, int feature)
     return (env->features & (1ULL << feature)) != 0;
 }
 
+/* Return true if the specified exception level is running in AArch64 state. */
+static inline bool arm_el_is_aa64(CPUARMState *env, int el)
+{
+    /* We don't currently support EL2 or EL3, and this isn't valid for EL0
+     * (if we're in EL0, is_a64() is what you want, and if we're not in EL0
+     * then the state of EL0 isn't well defined.)
+     */
+    assert(el == 1);
+    /* AArch64-capable CPUs always run with EL1 in AArch64 mode. This
+     * is a QEMU-imposed simplification which we may wish to change later.
+     * If we in future support EL2 and/or EL3, then the state of lower
+     * exception levels is controlled by the HCR.RW and SCR.RW bits.
+     */
+    return arm_feature(env, ARM_FEATURE_AARCH64);
+}
+
 void arm_cpu_list(FILE *f, fprintf_function cpu_fprintf);
 
 /* Interface between CPU and Interrupt controller.  */