target/arm: Fix aarch64_sve_change_el wrt EL0

At present we assert:

  arm_el_is_aa64: Assertion `el >= 1 && el <= 3' failed.

The comment in arm_el_is_aa64 explains why asking about EL0 without
extra information is impossible.  Add an extra argument to provide
it from the surrounding context.

Fixes: 0ab5953b00b3
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20181008212205.17752-2-richard.henderson@linaro.org
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

3 files changed, 22 insertions, 7 deletions

diff --git a/target/arm/cpu.h b/target/arm/cpu.h
index 3a2aff1192..54362ddce8 100644
--- a/target/arm/cpu.h
+++ b/target/arm/cpu.h
@@ -911,10 +911,13 @@ int arm_cpu_write_elf32_note(WriteCoreDumpFunction f, CPUState *cs,
 int aarch64_cpu_gdb_read_register(CPUState *cpu, uint8_t *buf, int reg);
 int aarch64_cpu_gdb_write_register(CPUState *cpu, uint8_t *buf, int reg);
 void aarch64_sve_narrow_vq(CPUARMState *env, unsigned vq);
-void aarch64_sve_change_el(CPUARMState *env, int old_el, int new_el);
+void aarch64_sve_change_el(CPUARMState *env, int old_el,
+                           int new_el, bool el0_a64);
 #else
 static inline void aarch64_sve_narrow_vq(CPUARMState *env, unsigned vq) { }
-static inline void aarch64_sve_change_el(CPUARMState *env, int o, int n) { }
+static inline void aarch64_sve_change_el(CPUARMState *env, int o,
+                                         int n, bool a)
+{ }
 #endif
 
 target_ulong do_arm_semihosting(CPUARMState *env);
diff --git a/target/arm/helper.c b/target/arm/helper.c
index c83f7c1109..0efbb5c76c 100644
--- a/target/arm/helper.c
+++ b/target/arm/helper.c
@@ -8374,7 +8374,11 @@ static void arm_cpu_do_interrupt_aarch64(CPUState *cs)
     unsigned int new_mode = aarch64_pstate_mode(new_el, true);
     unsigned int cur_el = arm_current_el(env);
 
-    aarch64_sve_change_el(env, cur_el, new_el);
+    /*
+     * Note that new_el can never be 0.  If cur_el is 0, then
+     * el0_a64 is is_a64(), else el0_a64 is ignored.
+     */
+    aarch64_sve_change_el(env, cur_el, new_el, is_a64(env));
 
     if (cur_el < new_el) {
         /* Entry vector offset depends on whether the implemented EL
@@ -12791,9 +12795,11 @@ void aarch64_sve_narrow_vq(CPUARMState *env, unsigned vq)
 /*
  * Notice a change in SVE vector size when changing EL.
  */
-void aarch64_sve_change_el(CPUARMState *env, int old_el, int new_el)
+void aarch64_sve_change_el(CPUARMState *env, int old_el,
+                           int new_el, bool el0_a64)
 {
     int old_len, new_len;
+    bool old_a64, new_a64;
 
     /* Nothing to do if no SVE.  */
     if (!arm_feature(env, ARM_FEATURE_SVE)) {
@@ -12817,9 +12823,11 @@ void aarch64_sve_change_el(CPUARMState *env, int old_el, int new_el)
      * we already have the correct register contents when encountering the
      * vq0->vq0 transition between EL0->EL1.
      */
-    old_len = (arm_el_is_aa64(env, old_el) && !sve_exception_el(env, old_el)
+    old_a64 = old_el ? arm_el_is_aa64(env, old_el) : el0_a64;
+    old_len = (old_a64 && !sve_exception_el(env, old_el)
                ? sve_zcr_len_for_el(env, old_el) : 0);
-    new_len = (arm_el_is_aa64(env, new_el) && !sve_exception_el(env, new_el)
+    new_a64 = new_el ? arm_el_is_aa64(env, new_el) : el0_a64;
+    new_len = (new_a64 && !sve_exception_el(env, new_el)
                ? sve_zcr_len_for_el(env, new_el) : 0);
 
     /* When changing vector length, clear inaccessible state.  */
diff --git a/target/arm/op_helper.c b/target/arm/op_helper.c
index fb15a13e6c..d915579712 100644
--- a/target/arm/op_helper.c
+++ b/target/arm/op_helper.c
@@ -1101,7 +1101,11 @@ void HELPER(exception_return)(CPUARMState *env)
                       "AArch64 EL%d PC 0x%" PRIx64 "\n",
                       cur_el, new_el, env->pc);
     }
-    aarch64_sve_change_el(env, cur_el, new_el);
+    /*
+     * Note that cur_el can never be 0.  If new_el is 0, then
+     * el0_a64 is return_to_aa64, else el0_a64 is ignored.
+     */
+    aarch64_sve_change_el(env, cur_el, new_el, return_to_aa64);
 
     qemu_mutex_lock_iothread();
     arm_call_el_change_hook(arm_env_get_cpu(env));