[v3,01/30] accel/tcg: Restrict cpu_handle_halt() to sysemu

Commit Message

Philippe Mathieu-Daudé Sept. 2, 2021, 4:15 p.m. UTC

Commit 372579427a5 ("tcg: enable thread-per-vCPU") added the following
comment describing EXCP_HALTED in qemu_tcg_cpu_thread_fn():

    case EXCP_HALTED:
         /* during start-up the vCPU is reset and the thread is
          * kicked several times. If we don't ensure we go back
          * to sleep in the halted state we won't cleanly
          * start-up when the vCPU is enabled.
          *
          * cpu->halted should ensure we sleep in wait_io_event
          */
         g_assert(cpu->halted);
         break;

qemu_wait_io_event() is sysemu-specific, so we can restrict the
cpu_handle_halt() call in cpu_exec() to system emulation.

Signed-off-by: Philippe Mathieu-Daudé <[e-mail]>
---
 accel/tcg/cpu-exec.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

Comments

Richard Henderson Sept. 3, 2021, 7:31 p.m. UTC | #1

On 9/2/21 6:15 PM, Philippe Mathieu-Daudé wrote:
> +#ifndef CONFIG_USER_ONLY
>   static inline bool cpu_handle_halt(CPUState *cpu)
>   {

Hmm, slightly better to move the ifdef just inside here,

> @@ -607,6 +608,7 @@ static inline bool cpu_handle_halt(CPUState *cpu)
>   

and here,

>       return false;
>   }
> +#endif /* !CONFIG_USER_ONLY */
>   
>   static inline void cpu_handle_debug_exception(CPUState *cpu)
>   {
> @@ -865,9 +867,11 @@ int cpu_exec(CPUState *cpu)
>       /* replay_interrupt may need current_cpu */
>       current_cpu = cpu;
>   
> +#ifndef CONFIG_USER_ONLY
>       if (cpu_handle_halt(cpu)) {
>           return EXCP_HALTED;
>       }
> +#endif

which would eliminate this one.


r~

Patch

diff --git a/accel/tcg/cpu-exec.c b/accel/tcg/cpu-exec.c
index 7a6dd9049f0..6b61262b151 100644
--- a/accel/tcg/cpu-exec.c
+++ b/accel/tcg/cpu-exec.c
@@ -586,10 +586,11 @@  static inline void tb_add_jump(TranslationBlock *tb, int n,
     return;
 }
 
+#ifndef CONFIG_USER_ONLY
 static inline bool cpu_handle_halt(CPUState *cpu)
 {
     if (cpu->halted) {
-#if defined(TARGET_I386) && !defined(CONFIG_USER_ONLY)
+#if defined(TARGET_I386)
         if (cpu->interrupt_request & CPU_INTERRUPT_POLL) {
             X86CPU *x86_cpu = X86_CPU(cpu);
             qemu_mutex_lock_iothread();
@@ -597,7 +598,7 @@  static inline bool cpu_handle_halt(CPUState *cpu)
             cpu_reset_interrupt(cpu, CPU_INTERRUPT_POLL);
             qemu_mutex_unlock_iothread();
         }
-#endif
+#endif /* TARGET_I386 */
         if (!cpu_has_work(cpu)) {
             return true;
         }
@@ -607,6 +608,7 @@  static inline bool cpu_handle_halt(CPUState *cpu)
 
     return false;
 }
+#endif /* !CONFIG_USER_ONLY */
 
 static inline void cpu_handle_debug_exception(CPUState *cpu)
 {
@@ -865,9 +867,11 @@  int cpu_exec(CPUState *cpu)
     /* replay_interrupt may need current_cpu */
     current_cpu = cpu;
 
+#ifndef CONFIG_USER_ONLY
     if (cpu_handle_halt(cpu)) {
         return EXCP_HALTED;
     }
+#endif
 
     rcu_read_lock();