target/nios2: Clean up nios2_cpu_do_interrupt

Split out do_exception and do_iic_irq to handle bulk of the interrupt and
exception processing.  Parameterize the changes required to cpu state.

The status.EH bit, which protects some data against double-faults,
is only present with the MMU.  Several exception cases did not check
for status.EH being set, as required.

The status.IH bit, which had been set by EXCP_IRQ, is exclusive to
the external interrupt controller, which we do not yet implement.
The internal interrupt controller, when the MMU is also present,
sets the status.EH bit.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20220421151735.31996-33-richard.henderson@linaro.org>

1 files changed, 44 insertions, 97 deletions

diff --git a/target/nios2/helper.c b/target/nios2/helper.c
index 1d17c0379f..63971a8b3c 100644
--- a/target/nios2/helper.c
+++ b/target/nios2/helper.c
@@ -29,6 +29,42 @@
 #include "semihosting/semihost.h"
 
 
+static void do_exception(Nios2CPU *cpu, uint32_t exception_addr, bool is_break)
+{
+    CPUNios2State *env = &cpu->env;
+    CPUState *cs = CPU(cpu);
+    uint32_t old_status = env->ctrl[CR_STATUS];
+    uint32_t new_status = old_status;
+
+    if ((old_status & CR_STATUS_EH) == 0) {
+        int r_ea = R_EA, cr_es = CR_ESTATUS;
+
+        if (is_break) {
+            r_ea = R_BA;
+            cr_es = CR_BSTATUS;
+        }
+        env->ctrl[cr_es] = old_status;
+        env->regs[r_ea] = env->pc + 4;
+
+        if (cpu->mmu_present) {
+            new_status |= CR_STATUS_EH;
+        }
+    }
+
+    new_status &= ~(CR_STATUS_PIE | CR_STATUS_U);
+
+    env->ctrl[CR_STATUS] = new_status;
+    env->ctrl[CR_EXCEPTION] = FIELD_DP32(env->ctrl[CR_EXCEPTION],
+                                         CR_EXCEPTION, CAUSE,
+                                         cs->exception_index);
+    env->pc = exception_addr;
+}
+
+static void do_iic_irq(Nios2CPU *cpu)
+{
+    do_exception(cpu, cpu->exception_addr, false);
+}
+
 void nios2_cpu_do_interrupt(CPUState *cs)
 {
     Nios2CPU *cpu = NIOS2_CPU(cs);
@@ -36,57 +72,20 @@ void nios2_cpu_do_interrupt(CPUState *cs)
 
     switch (cs->exception_index) {
     case EXCP_IRQ:
-        assert(env->ctrl[CR_STATUS] & CR_STATUS_PIE);
-
         qemu_log_mask(CPU_LOG_INT, "interrupt at pc=%x\n", env->pc);
-
-        env->ctrl[CR_ESTATUS] = env->ctrl[CR_STATUS];
-        env->ctrl[CR_STATUS] |= CR_STATUS_IH;
-        env->ctrl[CR_STATUS] &= ~(CR_STATUS_PIE | CR_STATUS_U);
-
-        env->ctrl[CR_EXCEPTION] = FIELD_DP32(env->ctrl[CR_EXCEPTION],
-                                             CR_EXCEPTION, CAUSE,
-                                             cs->exception_index);
-
-        env->regs[R_EA] = env->pc + 4;
-        env->pc = cpu->exception_addr;
+        do_iic_irq(cpu);
         break;
 
     case EXCP_TLBD:
         if ((env->ctrl[CR_STATUS] & CR_STATUS_EH) == 0) {
             qemu_log_mask(CPU_LOG_INT, "TLB MISS (fast) at pc=%x\n", env->pc);
-
-            /* Fast TLB miss */
-            /* Variation from the spec. Table 3-35 of the cpu reference shows
-             * estatus not being changed for TLB miss but this appears to
-             * be incorrect. */
-            env->ctrl[CR_ESTATUS] = env->ctrl[CR_STATUS];
-            env->ctrl[CR_STATUS] |= CR_STATUS_EH;
-            env->ctrl[CR_STATUS] &= ~(CR_STATUS_PIE | CR_STATUS_U);
-
-            env->ctrl[CR_EXCEPTION] = FIELD_DP32(env->ctrl[CR_EXCEPTION],
-                                                 CR_EXCEPTION, CAUSE,
-                                                 cs->exception_index);
-
             env->ctrl[CR_TLBMISC] &= ~CR_TLBMISC_DBL;
             env->ctrl[CR_TLBMISC] |= CR_TLBMISC_WE;
-
-            env->regs[R_EA] = env->pc + 4;
-            env->pc = cpu->fast_tlb_miss_addr;
+            do_exception(cpu, cpu->fast_tlb_miss_addr, false);
         } else {
             qemu_log_mask(CPU_LOG_INT, "TLB MISS (double) at pc=%x\n", env->pc);
-
-            /* Double TLB miss */
-            env->ctrl[CR_STATUS] |= CR_STATUS_EH;
-            env->ctrl[CR_STATUS] &= ~(CR_STATUS_PIE | CR_STATUS_U);
-
-            env->ctrl[CR_EXCEPTION] = FIELD_DP32(env->ctrl[CR_EXCEPTION],
-                                                 CR_EXCEPTION, CAUSE,
-                                                 cs->exception_index);
-
             env->ctrl[CR_TLBMISC] |= CR_TLBMISC_DBL;
-
-            env->pc = cpu->exception_addr;
+            do_exception(cpu, cpu->exception_addr, false);
         }
         break;
 
@@ -94,78 +93,28 @@ void nios2_cpu_do_interrupt(CPUState *cs)
     case EXCP_TLBW:
     case EXCP_TLBX:
         qemu_log_mask(CPU_LOG_INT, "TLB PERM at pc=%x\n", env->pc);
-
-        env->ctrl[CR_ESTATUS] = env->ctrl[CR_STATUS];
-        env->ctrl[CR_STATUS] |= CR_STATUS_EH;
-        env->ctrl[CR_STATUS] &= ~(CR_STATUS_PIE | CR_STATUS_U);
-
-        env->ctrl[CR_EXCEPTION] = FIELD_DP32(env->ctrl[CR_EXCEPTION],
-                                             CR_EXCEPTION, CAUSE,
-                                             cs->exception_index);
-
         if ((env->ctrl[CR_STATUS] & CR_STATUS_EH) == 0) {
             env->ctrl[CR_TLBMISC] |= CR_TLBMISC_WE;
         }
-
-        env->regs[R_EA] = env->pc + 4;
-        env->pc = cpu->exception_addr;
+        do_exception(cpu, cpu->exception_addr, false);
         break;
 
     case EXCP_SUPERA:
     case EXCP_SUPERI:
     case EXCP_SUPERD:
         qemu_log_mask(CPU_LOG_INT, "SUPERVISOR exception at pc=%x\n", env->pc);
-
-        if ((env->ctrl[CR_STATUS] & CR_STATUS_EH) == 0) {
-            env->ctrl[CR_ESTATUS] = env->ctrl[CR_STATUS];
-            env->regs[R_EA] = env->pc + 4;
-        }
-
-        env->ctrl[CR_STATUS] |= CR_STATUS_EH;
-        env->ctrl[CR_STATUS] &= ~(CR_STATUS_PIE | CR_STATUS_U);
-
-        env->ctrl[CR_EXCEPTION] = FIELD_DP32(env->ctrl[CR_EXCEPTION],
-                                             CR_EXCEPTION, CAUSE,
-                                             cs->exception_index);
-
-        env->pc = cpu->exception_addr;
+        do_exception(cpu, cpu->exception_addr, false);
         break;
 
     case EXCP_ILLEGAL:
     case EXCP_TRAP:
         qemu_log_mask(CPU_LOG_INT, "TRAP exception at pc=%x\n", env->pc);
-
-        if ((env->ctrl[CR_STATUS] & CR_STATUS_EH) == 0) {
-            env->ctrl[CR_ESTATUS] = env->ctrl[CR_STATUS];
-            env->regs[R_EA] = env->pc + 4;
-        }
-
-        env->ctrl[CR_STATUS] |= CR_STATUS_EH;
-        env->ctrl[CR_STATUS] &= ~(CR_STATUS_PIE | CR_STATUS_U);
-
-        env->ctrl[CR_EXCEPTION] = FIELD_DP32(env->ctrl[CR_EXCEPTION],
-                                             CR_EXCEPTION, CAUSE,
-                                             cs->exception_index);
-
-        env->pc = cpu->exception_addr;
+        do_exception(cpu, cpu->exception_addr, false);
         break;
 
     case EXCP_BREAK:
         qemu_log_mask(CPU_LOG_INT, "BREAK exception at pc=%x\n", env->pc);
-
-        if ((env->ctrl[CR_STATUS] & CR_STATUS_EH) == 0) {
-            env->ctrl[CR_BSTATUS] = env->ctrl[CR_STATUS];
-            env->regs[R_BA] = env->pc + 4;
-        }
-
-        env->ctrl[CR_STATUS] |= CR_STATUS_EH;
-        env->ctrl[CR_STATUS] &= ~(CR_STATUS_PIE | CR_STATUS_U);
-
-        env->ctrl[CR_EXCEPTION] = FIELD_DP32(env->ctrl[CR_EXCEPTION],
-                                             CR_EXCEPTION, CAUSE,
-                                             cs->exception_index);
-
-        env->pc = cpu->exception_addr;
+        do_exception(cpu, cpu->exception_addr, true);
         break;
 
     case EXCP_SEMIHOST:
@@ -175,9 +124,7 @@ void nios2_cpu_do_interrupt(CPUState *cs)
         break;
 
     default:
-        cpu_abort(cs, "unhandled exception type=%d\n",
-                  cs->exception_index);
-        break;
+        cpu_abort(cs, "unhandled exception type=%d\n", cs->exception_index);
     }
 }