For simplicity keep the OP as a two bit field rather than the two
interlinked fields in the docs (ERET/ERETA).

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
---
 target/arm/syndrome.h | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/target/arm/syndrome.h b/target/arm/syndrome.h
index 5b5a5cb182e..b145a52769f 100644
--- a/target/arm/syndrome.h
+++ b/target/arm/syndrome.h
@@ -367,12 +367,21 @@ static inline uint32_t syn_sve_access_trap(void)
 }
 
 /*
+ * ISS encoding for an exception from an ERET, ERETAA or ERETAB
+ * instructions.
+ *
  * eret_op is bits [1:0] of the ERET instruction, so:
  * 0 for ERET, 2 for ERETAA, 3 for ERETAB.
  */
+FIELD(ERET_ISS, OP, 0, 2)
+
 static inline uint32_t syn_erettrap(int eret_op)
 {
-    return (EC_ERETTRAP << ARM_EL_EC_SHIFT) | ARM_EL_IL | eret_op;
+    uint32_t res = syn_set_ec(0, EC_ERETTRAP);
+    res = FIELD_DP32(res, SYNDROME, IL, 1);
+    res = FIELD_DP32(res, ERET_ISS, OP, eret_op);
+
+    return res;
 }
 
 static inline uint32_t syn_smetrap(SMEExceptionType etype, bool is_16bit)
-- 
2.47.3