From: Richard Henderson <richard.henderson@linaro.org>

This does not attempt to rectify all of the res0 bits, but does
clear the mte bits when not enabled.  Since there is no high-part
mapping of SCTLR, aa32 mode cannot write to these bits.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20200626033144.790098-4-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target/arm/helper.c | 23 +++++++++++++++++------
 1 file changed, 17 insertions(+), 6 deletions(-)

diff --git a/target/arm/helper.c b/target/arm/helper.c
index a29f0a28d84..8a0fb015819 100644
--- a/target/arm/helper.c
+++ b/target/arm/helper.c
@@ -4698,6 +4698,22 @@ static void sctlr_write(CPUARMState *env, const ARMCPRegInfo *ri,
 {
     ARMCPU *cpu = env_archcpu(env);
 
+    if (arm_feature(env, ARM_FEATURE_PMSA) && !cpu->has_mpu) {
+        /* M bit is RAZ/WI for PMSA with no MPU implemented */
+        value &= ~SCTLR_M;
+    }
+
+    /* ??? Lots of these bits are not implemented.  */
+
+    if (ri->state == ARM_CP_STATE_AA64 && !cpu_isar_feature(aa64_mte, cpu)) {
+        if (ri->opc1 == 6) { /* SCTLR_EL3 */
+            value &= ~(SCTLR_ITFSB | SCTLR_TCF | SCTLR_ATA);
+        } else {
+            value &= ~(SCTLR_ITFSB | SCTLR_TCF0 | SCTLR_TCF |
+                       SCTLR_ATA0 | SCTLR_ATA);
+        }
+    }
+
     if (raw_read(env, ri) == value) {
         /* Skip the TLB flush if nothing actually changed; Linux likes
          * to do a lot of pointless SCTLR writes.
@@ -4705,13 +4721,8 @@ static void sctlr_write(CPUARMState *env, const ARMCPRegInfo *ri,
         return;
     }
 
-    if (arm_feature(env, ARM_FEATURE_PMSA) && !cpu->has_mpu) {
-        /* M bit is RAZ/WI for PMSA with no MPU implemented */
-        value &= ~SCTLR_M;
-    }
-
     raw_write(env, ri, value);
-    /* ??? Lots of these bits are not implemented.  */
+
     /* This may enable/disable the MMU, so do a TLB flush.  */
     tlb_flush(CPU(cpu));
 
-- 
2.20.1