[Qemu-devel] [PATCH v2 07/27] tcg: Add EXCP_ATOMIC

[Richard Henderson]

When we cannot emulate an atomic operation within a parallel
context, this exception allows us to stop the world and try
again in a serial context.

Signed-off-by: Richard Henderson <address@hidden>
---
 cpu-exec-common.c       |  6 +++++
 cpu-exec.c              | 23 +++++++++++++++++++
 cpus.c                  |  6 +++++
 include/exec/cpu-all.h  |  1 +
 include/exec/exec-all.h |  1 +
 include/qemu-common.h   |  1 +
 linux-user/main.c       | 59 ++++++++++++++++++++++++++++++++++++++++++++++++-
 tcg/tcg.h               |  1 +
 translate-all.c         |  1 +
 9 files changed, 98 insertions(+), 1 deletion(-)

diff --git a/cpu-exec-common.c b/cpu-exec-common.c
index 0cb4ae6..767d9c6 100644
--- a/cpu-exec-common.c
+++ b/cpu-exec-common.c
@@ -77,3 +77,9 @@ void cpu_loop_exit_restore(CPUState *cpu, uintptr_t pc)
     }
     siglongjmp(cpu->jmp_env, 1);
 }
+
+void cpu_loop_exit_atomic(CPUState *cpu, uintptr_t pc)
+{
+    cpu->exception_index = EXCP_ATOMIC;
+    cpu_loop_exit_restore(cpu, pc);
+}
diff --git a/cpu-exec.c b/cpu-exec.c
index b840e1d..041f8b7 100644
--- a/cpu-exec.c
+++ b/cpu-exec.c
@@ -225,6 +225,29 @@ static void cpu_exec_nocache(CPUState *cpu, int max_cycles,
 }
 #endif
 
+void cpu_exec_step(CPUState *cpu)
+{
+    CPUArchState *env = (CPUArchState *)cpu->env_ptr;
+    TranslationBlock *tb;
+    target_ulong cs_base, pc;
+    uint32_t flags;
+    bool old_tb_flushed;
+
+    old_tb_flushed = cpu->tb_flushed;
+    cpu->tb_flushed = false;
+
+    cpu_get_tb_cpu_state(env, &pc, &cs_base, &flags);
+    tb = tb_gen_code(cpu, pc, cs_base, flags,
+                     1 | CF_NOCACHE | CF_IGNORE_ICOUNT);
+    tb->orig_tb = NULL;
+    cpu->tb_flushed |= old_tb_flushed;
+    /* execute the generated code */
+    trace_exec_tb_nocache(tb, pc);
+    cpu_tb_exec(cpu, tb);
+    tb_phys_invalidate(tb, -1);
+    tb_free(tb);
+}
+
 struct tb_desc {
     target_ulong pc;
     target_ulong cs_base;
diff --git a/cpus.c b/cpus.c
index 84c3520..a01bbbd 100644
--- a/cpus.c
+++ b/cpus.c
@@ -1575,6 +1575,12 @@ static void tcg_exec_all(void)
             if (r == EXCP_DEBUG) {
                 cpu_handle_guest_debug(cpu);
                 break;
+            } else if (r == EXCP_ATOMIC) {
+                /* ??? When we begin running cpus in parallel, we should
+                   stop all cpus, clear parallel_cpus, and interpret a
+                   single insn with cpu_exec_step.  In the meantime,
+                   we should never get here.  */
+                abort();
             }
         } else if (cpu->stop || cpu->stopped) {
             if (cpu->unplug) {
diff --git a/include/exec/cpu-all.h b/include/exec/cpu-all.h
index 8007abb..d2aac4b 100644
--- a/include/exec/cpu-all.h
+++ b/include/exec/cpu-all.h
@@ -31,6 +31,7 @@
 #define EXCP_DEBUG      0x10002 /* cpu stopped after a breakpoint or 
singlestep */
 #define EXCP_HALTED     0x10003 /* cpu is halted (waiting for external event) 
*/
 #define EXCP_YIELD      0x10004 /* cpu wants to yield timeslice to another */
+#define EXCP_ATOMIC     0x10005 /* stop-the-world and emulate atomic */
 
 /* some important defines:
  *
diff --git a/include/exec/exec-all.h b/include/exec/exec-all.h
index c1f59fa..ec72c5a 100644
--- a/include/exec/exec-all.h
+++ b/include/exec/exec-all.h
@@ -59,6 +59,7 @@ TranslationBlock *tb_gen_code(CPUState *cpu,
 void cpu_exec_init(CPUState *cpu, Error **errp);
 void QEMU_NORETURN cpu_loop_exit(CPUState *cpu);
 void QEMU_NORETURN cpu_loop_exit_restore(CPUState *cpu, uintptr_t pc);
+void QEMU_NORETURN cpu_loop_exit_atomic(CPUState *cpu, uintptr_t pc);
 
 #if !defined(CONFIG_USER_ONLY)
 void cpu_reloading_memory_map(void);
diff --git a/include/qemu-common.h b/include/qemu-common.h
index 1f2cb94..77e379d 100644
--- a/include/qemu-common.h
+++ b/include/qemu-common.h
@@ -76,6 +76,7 @@ void tcg_exec_init(unsigned long tb_size);
 bool tcg_enabled(void);
 
 void cpu_exec_init_all(void);
+void cpu_exec_step(CPUState *cpu);
 
 /**
  * Sends a (part of) iovec down a socket, yielding when the socket is full, or
diff --git a/linux-user/main.c b/linux-user/main.c
index 78d8d04..54df300 100644
--- a/linux-user/main.c
+++ b/linux-user/main.c
@@ -179,13 +179,25 @@ static inline void start_exclusive(void)
 }
 
 /* Finish an exclusive operation.  */
-static inline void __attribute__((unused)) end_exclusive(void)
+static inline void end_exclusive(void)
 {
     pending_cpus = 0;
     pthread_cond_broadcast(&exclusive_resume);
     pthread_mutex_unlock(&exclusive_lock);
 }
 
+static void step_atomic(CPUState *cpu)
+{
+    start_exclusive();
+
+    /* Since we got here, we know that parallel_cpus must be true.  */
+    parallel_cpus = false;
+    cpu_exec_step(cpu);
+    parallel_cpus = true;
+
+    end_exclusive();
+}
+
 /* Wait for exclusive ops to finish, and begin cpu execution.  */
 static inline void cpu_exec_start(CPUState *cpu)
 {
@@ -437,6 +449,9 @@ void cpu_loop(CPUX86State *env)
                   }
             }
             break;
+        case EXCP_ATOMIC:
+            step_atomic(cs);
+            break;
         default:
             pc = env->segs[R_CS].base + env->eip;
             EXCP_DUMP(env, "qemu: 0x%08lx: unhandled CPU exception 0x%x - 
aborting\n",
@@ -929,6 +944,9 @@ void cpu_loop(CPUARMState *env)
         case EXCP_YIELD:
             /* nothing to do here for user-mode, just resume guest code */
             break;
+        case EXCP_ATOMIC:
+            step_atomic(cs);
+            break;
         default:
         error:
             EXCP_DUMP(env, "qemu: unhandled CPU exception 0x%x - aborting\n", 
trapnr);
@@ -1128,6 +1146,9 @@ void cpu_loop(CPUARMState *env)
         case EXCP_YIELD:
             /* nothing to do here for user-mode, just resume guest code */
             break;
+        case EXCP_ATOMIC:
+            step_atomic(cs);
+            break;
         default:
             EXCP_DUMP(env, "qemu: unhandled CPU exception 0x%x - aborting\n", 
trapnr);
             abort();
@@ -1217,6 +1238,9 @@ void cpu_loop(CPUUniCore32State *env)
                 }
             }
             break;
+        case EXCP_ATOMIC:
+            step_atomic(cs);
+            break;
         default:
             goto error;
         }
@@ -1489,6 +1513,9 @@ void cpu_loop (CPUSPARCState *env)
                   }
             }
             break;
+        case EXCP_ATOMIC:
+            step_atomic(cs);
+            break;
         default:
             printf ("Unhandled trap: 0x%x\n", trapnr);
             cpu_dump_state(cs, stderr, fprintf, 0);
@@ -2037,6 +2064,9 @@ void cpu_loop(CPUPPCState *env)
         case EXCP_INTERRUPT:
             /* just indicate that signals should be handled asap */
             break;
+        case EXCP_ATOMIC:
+            step_atomic(cs);
+            break;
         default:
             cpu_abort(cs, "Unknown exception 0x%d. Aborting\n", trapnr);
             break;
@@ -2710,6 +2740,9 @@ done_syscall:
                 }
             }
             break;
+        case EXCP_ATOMIC:
+            step_atomic(cs);
+            break;
         default:
 error:
             EXCP_DUMP(env, "qemu: unhandled CPU exception 0x%x - aborting\n", 
trapnr);
@@ -2796,6 +2829,9 @@ void cpu_loop(CPUOpenRISCState *env)
         case EXCP_NR:
             qemu_log_mask(CPU_LOG_INT, "\nNR\n");
             break;
+        case EXCP_ATOMIC:
+            step_atomic(cs);
+            break;
         default:
             EXCP_DUMP(env, "\nqemu: unhandled CPU exception %#x - aborting\n",
                      trapnr);
@@ -2871,6 +2907,9 @@ void cpu_loop(CPUSH4State *env)
             queue_signal(env, info.si_signo, &info);
            break;
 
+        case EXCP_ATOMIC:
+            step_atomic(cs);
+            break;
         default:
             printf ("Unhandled trap: 0x%x\n", trapnr);
             cpu_dump_state(cs, stderr, fprintf, 0);
@@ -2936,6 +2975,9 @@ void cpu_loop(CPUCRISState *env)
                   }
             }
             break;
+        case EXCP_ATOMIC:
+            step_atomic(cs);
+            break;
         default:
             printf ("Unhandled trap: 0x%x\n", trapnr);
             cpu_dump_state(cs, stderr, fprintf, 0);
@@ -3050,6 +3092,9 @@ void cpu_loop(CPUMBState *env)
                   }
             }
             break;
+        case EXCP_ATOMIC:
+            step_atomic(cs);
+            break;
         default:
             printf ("Unhandled trap: 0x%x\n", trapnr);
             cpu_dump_state(cs, stderr, fprintf, 0);
@@ -3151,6 +3196,9 @@ void cpu_loop(CPUM68KState *env)
                   }
             }
             break;
+        case EXCP_ATOMIC:
+            step_atomic(cs);
+            break;
         default:
             EXCP_DUMP(env, "qemu: unhandled CPU exception 0x%x - aborting\n", 
trapnr);
             abort();
@@ -3386,6 +3434,9 @@ void cpu_loop(CPUAlphaState *env)
         case EXCP_INTERRUPT:
             /* Just indicate that signals should be handled asap.  */
             break;
+        case EXCP_ATOMIC:
+            step_atomic(cs);
+            break;
         default:
             printf ("Unhandled trap: 0x%x\n", trapnr);
             cpu_dump_state(cs, stderr, fprintf, 0);
@@ -3513,6 +3564,9 @@ void cpu_loop(CPUS390XState *env)
             queue_signal(env, info.si_signo, &info);
             break;
 
+        case EXCP_ATOMIC:
+            step_atomic(cs);
+            break;
         default:
             fprintf(stderr, "Unhandled trap: 0x%x\n", trapnr);
             cpu_dump_state(cs, stderr, fprintf, 0);
@@ -3765,6 +3819,9 @@ void cpu_loop(CPUTLGState *env)
         case TILEGX_EXCP_REG_UDN_ACCESS:
             gen_sigill_reg(env);
             break;
+        case EXCP_ATOMIC:
+            step_atomic(cs);
+            break;
         default:
             fprintf(stderr, "trapnr is %d[0x%x].\n", trapnr, trapnr);
             g_assert_not_reached();
diff --git a/tcg/tcg.h b/tcg/tcg.h
index 66ae0c7..ab67537 100644
--- a/tcg/tcg.h
+++ b/tcg/tcg.h
@@ -691,6 +691,7 @@ struct TCGContext {
 };
 
 extern TCGContext tcg_ctx;
+extern bool parallel_cpus;
 
 static inline void tcg_set_insn_param(int op_idx, int arg, TCGArg v)
 {
diff --git a/translate-all.c b/translate-all.c
index eaa95e4..99ae7f9 100644
--- a/translate-all.c
+++ b/translate-all.c
@@ -119,6 +119,7 @@ static void *l1_map[V_L1_SIZE];
 
 /* code generation context */
 TCGContext tcg_ctx;
+bool parallel_cpus;
 
 /* translation block context */
 #ifdef CONFIG_USER_ONLY
-- 
2.5.5