target/arm: Reset streaming sve state on exception boundaries

We can handle both exception entry and exception return by
hooking into aarch64_sve_change_el.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20220708151540.18136-32-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

diff --git a/target/arm/helper.c b/target/arm/helper.c
index 73a5b2b86d9d656f5d557afa7ea0be07ce4c826c..cfcad97ce078efc6750f65ecf5ddcbcb22607e86 100644 (file)
--- a/target/arm/helper.c
+++ b/target/arm/helper.c
@@ -11242,6 +11242,19 @@ void aarch64_sve_change_el(CPUARMState *env, int old_el,
         return;
     }
 
+    old_a64 = old_el ? arm_el_is_aa64(env, old_el) : el0_a64;
+    new_a64 = new_el ? arm_el_is_aa64(env, new_el) : el0_a64;
+
+    /*
+     * Both AArch64.TakeException and AArch64.ExceptionReturn
+     * invoke ResetSVEState when taking an exception from, or
+     * returning to, AArch32 state when PSTATE.SM is enabled.
+     */
+    if (old_a64 != new_a64 && FIELD_EX64(env->svcr, SVCR, SM)) {
+        arm_reset_sve_state(env);
+        return;
+    }
+
     /*
      * DDI0584A.d sec 3.2: "If SVE instructions are disabled or trapped
      * at ELx, or not available because the EL is in AArch32 state, then
@@ -11254,10 +11267,8 @@ void aarch64_sve_change_el(CPUARMState *env, int old_el,
      * we already have the correct register contents when encountering the
      * vq0->vq0 transition between EL0->EL1.
      */
-    old_a64 = old_el ? arm_el_is_aa64(env, old_el) : el0_a64;
     old_len = (old_a64 && !sve_exception_el(env, old_el)
                ? sve_vqm1_for_el(env, old_el) : 0);
-    new_a64 = new_el ? arm_el_is_aa64(env, new_el) : el0_a64;
     new_len = (new_a64 && !sve_exception_el(env, new_el)
                ? sve_vqm1_for_el(env, new_el) : 0);