target/arm: Add commentary for CPUARMState.exclusive_high
Document the meaning of exclusive_high in a big-endian context,
and why we can't change it now.
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20230530191438.411344-2-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
diff --git a/target/arm/cpu.h b/target/arm/cpu.h
index d469a26..81c0df9 100644
--- a/target/arm/cpu.h
+++ b/target/arm/cpu.h
@@ -677,8 +677,16 @@
uint64_t zcr_el[4]; /* ZCR_EL[1-3] */
uint64_t smcr_el[4]; /* SMCR_EL[1-3] */
} vfp;
+
uint64_t exclusive_addr;
uint64_t exclusive_val;
+ /*
+ * Contains the 'val' for the second 64-bit register of LDXP, which comes
+ * from the higher address, not the high part of a complete 128-bit value.
+ * In some ways it might be more convenient to record the exclusive value
+ * as the low and high halves of a 128 bit data value, but the current
+ * semantics of these fields are baked into the migration format.
+ */
uint64_t exclusive_high;
/* iwMMXt coprocessor state. */
