[PATCH v2 04/11] target/arm: When tag memory is not present, set MTE=1

[Richard Henderson <richard.henderson@linaro.org>]

When the cpu support MTE, but the system does not, reduce cpu
support to user instructions at EL0 instead of completely
disabling MTE.  If we encounter a cpu implementation which does
something else, we can revisit this setting.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 target/arm/cpu.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/target/arm/cpu.c b/target/arm/cpu.c
index 37e8c35677..85c02308e4 100644
--- a/target/arm/cpu.c
+++ b/target/arm/cpu.c
@@ -2067,12 +2067,13 @@ static void arm_cpu_realizefn(DeviceState *dev, Error **errp)
 
 #ifndef CONFIG_USER_ONLY
         /*
-         * Disable the MTE feature bits if we do not have tag-memory
-         * provided by the machine.
+         * If we do not have tag-memory provided by the machine,
+         * reduce MTE support to instructions enabled at EL0.
+         * This matches Cortex-A710 BROADCASTMTE input being LOW.
          */
         if (cpu->tag_memory == NULL) {
             cpu->isar.id_aa64pfr1 =
-                FIELD_DP64(cpu->isar.id_aa64pfr1, ID_AA64PFR1, MTE, 0);
+                FIELD_DP64(cpu->isar.id_aa64pfr1, ID_AA64PFR1, MTE, 1);
         }
 #endif
     }
-- 
2.34.1