target-arm: Provide hook to tell GICv3 about changes of security state

The GICv3 CPU interface needs to know when the CPU it is attached
to makes an exception level or mode transition that changes the
security state, because whether it is asserting IRQ or FIQ can change
depending on these things. Provide a mechanism for letting the GICv3
device register a hook to be called on such changes.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Shannon Zhao <shannon.zhao@linaro.org>
Tested-by: Shannon Zhao <shannon.zhao@linaro.org>
Message-id: 1465915112-29272-5-git-send-email-peter.maydell@linaro.org

target-arm/cpu.c

@@ -51,6 +51,15 @@ static bool arm_cpu_has_work(CPUState *cs)
          | CPU_INTERRUPT_EXITTB);
 }
 
+void arm_register_el_change_hook(ARMCPU *cpu, ARMELChangeHook *hook,
+                                 void *opaque)
+{
+    /* We currently only support registering a single hook function */
+    assert(!cpu->el_change_hook);
+    cpu->el_change_hook = hook;
+    cpu->el_change_hook_opaque = opaque;
+}
+
 static void cp_reg_reset(gpointer key, gpointer value, gpointer opaque)
 {
     /* Reset a single ARMCPRegInfo register */

target-arm/cpu.h

@@ -514,6 +514,13 @@ typedef struct CPUARMState {
     const struct arm_boot_info *boot_info;
 } CPUARMState;
 
+/**
+ * ARMELChangeHook:
+ * type of a function which can be registered via arm_register_el_change_hook()
+ * to get callbacks when the CPU changes its exception level or mode.
+ */
+typedef void ARMELChangeHook(ARMCPU *cpu, void *opaque);
+
 /**
  * ARMCPU:
  * @env: #CPUARMState
@@ -654,6 +661,9 @@ struct ARMCPU {
     /* DCZ blocksize, in log_2(words), ie low 4 bits of DCZID_EL0 */
     uint32_t dcz_blocksize;
     uint64_t rvbar;
+
+    ARMELChangeHook *el_change_hook;
+    void *el_change_hook_opaque;
 };
 
 static inline ARMCPU *arm_env_get_cpu(CPUARMState *env)
@@ -2386,4 +2396,28 @@ static inline AddressSpace *arm_addressspace(CPUState *cs, MemTxAttrs attrs)
 }
 #endif
 
+/**
+ * arm_register_el_change_hook:
+ * Register a hook function which will be called back whenever this
+ * CPU changes exception level or mode. The hook function will be
+ * passed a pointer to the ARMCPU and the opaque data pointer passed
+ * to this function when the hook was registered.
+ *
+ * Note that we currently only support registering a single hook function,
+ * and will assert if this function is called twice.
+ * This facility is intended for the use of the GICv3 emulation.
+ */
+void arm_register_el_change_hook(ARMCPU *cpu, ARMELChangeHook *hook,
+                                 void *opaque);
+
+/**
+ * arm_get_el_change_hook_opaque:
+ * Return the opaque data that will be used by the el_change_hook
+ * for this CPU.
+ */
+static inline void *arm_get_el_change_hook_opaque(ARMCPU *cpu)
+{
+    return cpu->el_change_hook_opaque;
+}
+
 #endif

target-arm/helper.c

@@ -6503,6 +6503,8 @@ void arm_cpu_do_interrupt(CPUState *cs)
         arm_cpu_do_interrupt_aarch32(cs);
     }
 
+    arm_call_el_change_hook(cpu);
+
     if (!kvm_enabled()) {
         cs->interrupt_request |= CPU_INTERRUPT_EXITTB;
     }

target-arm/internals.h

@@ -479,4 +479,12 @@ bool arm_s1_regime_using_lpae_format(CPUARMState *env, ARMMMUIdx mmu_idx);
 void arm_cpu_do_unaligned_access(CPUState *cs, vaddr vaddr, int is_write,
                                  int is_user, uintptr_t retaddr);
 
+/* Call the EL change hook if one has been registered */
+static inline void arm_call_el_change_hook(ARMCPU *cpu)
+{
+    if (cpu->el_change_hook) {
+        cpu->el_change_hook(cpu, cpu->el_change_hook_opaque);
+    }
+}
+
 #endif

target-arm/op_helper.c

@@ -474,6 +474,8 @@ void HELPER(cpsr_write)(CPUARMState *env, uint32_t val, uint32_t mask)
 void HELPER(cpsr_write_eret)(CPUARMState *env, uint32_t val)
 {
     cpsr_write(env, val, CPSR_ERET_MASK, CPSRWriteExceptionReturn);
+
+    arm_call_el_change_hook(arm_env_get_cpu(env));
 }
 
 /* Access to user mode registers from privileged modes.  */
@@ -969,6 +971,8 @@ void HELPER(exception_return)(CPUARMState *env)
         env->pc = env->elr_el[cur_el];
     }
 
+    arm_call_el_change_hook(arm_env_get_cpu(env));
+
     return;
 
 illegal_return: