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References: <20180409091320.12504.35329.stgit@pasha-VirtualBox>
From: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <3c1eeffa-6fbb-1edf-296a-6bc7fabab26d@redhat.com>
Date: Tue, 10 Apr 2018 09:35:41 +0200
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Subject: Re: [Qemu-devel] [PATCH] icount: fix cpu_restore_state_from_tb for
 non-tb-exit cases
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To: Pavel Dovgalyuk <Pavel.Dovgaluk@ispras.ru>, qemu-devel@nongnu.org
Cc: peter.maydell@linaro.org, ehabkost@redhat.com, crosthwaite.peter@gmail.com, kbastian@mail.uni-paderborn.de, green@moxielogic.com, laurent@vivier.eu, jcmvbkbc@gmail.com, maria.klimushenkova@ispras.ru, dovgaluk@ispras.ru, edgar.iglesias@gmail.com, shorne@gmail.com, yongbok.kim@mips.com, aurelien@aurel32.net, rth@twiddle.net

On 09/04/2018 11:13, Pavel Dovgalyuk wrote:
> @@ -29,6 +29,7 @@ void cpu_loop_exit_noexc(CPUState *cpu)
>  {
>      /* XXX: restore cpu registers saved in host registers */
>  
> +    cpu->can_do_io = !use_icount;
>      cpu->exception_index = -1;
>      siglongjmp(cpu->jmp_env, 1);
>  }
> @@ -65,14 +66,16 @@ void cpu_reloading_memory_map(void)
>  
>  void cpu_loop_exit(CPUState *cpu)
>  {
> +    cpu->can_do_io = !use_icount;
>      siglongjmp(cpu->jmp_env, 1);
>  }
>  
>  void cpu_loop_exit_restore(CPUState *cpu, uintptr_t pc)
>  {
>      if (pc) {
> -        cpu_restore_state(cpu, pc);
> +        cpu_restore_state(cpu, pc, true);
>      }
> +    cpu->can_do_io = !use_icount;
>      siglongjmp(cpu->jmp_env, 1);
>  }

This is incorrect, "cpu->can_do_io" is 1 when not in tcg_qemu_tb_exec.
In fact, in cpu_exec we have "cpu->can_do_io = 1;" immediately after
siglongjmp, so I propose adding the same "cpu->can_do_io = 1;"
assignment to cpu_exec_step_atomic.

In any case, please change the two siglongjmp of
cpu_loop_exit_{noexc,restore} to cpu_loop_exit, instead of duplicating
that cpu->can_do_io assignment.

Thanks,

Paolo