target/arm: Enable TBI for user-only

This has been enabled in the linux kernel since v3.11
(commit d50240a5f6cea, 2013-09-03,
"arm64: mm: permit use of tagged pointers at EL0").

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20190204132126.3255-5-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

target/arm/cpu.c

@@ -200,6 +200,12 @@ static void arm_cpu_reset(CPUState *s)
         env->vfp.zcr_el[1] = cpu->sve_max_vq - 1;
         env->vfp.zcr_el[2] = env->vfp.zcr_el[1];
         env->vfp.zcr_el[3] = env->vfp.zcr_el[1];
+        /*
+         * Enable TBI0 and TBI1.  While the real kernel only enables TBI0,
+         * turning on both here will produce smaller code and otherwise
+         * make no difference to the user-level emulation.
+         */
+        env->cp15.tcr_el[1].raw_tcr = (3ULL << 37);
 #else
         /* Reset into the highest available EL */
         if (arm_feature(env, ARM_FEATURE_EL3)) {