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Date: Tue, 30 Jun 2015 15:10:50 +0100
From: Leon Alrae <leon.alrae@imgtec.com>
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Subject: Re: [Qemu-devel] [PATCH pic32 2/7] Stop simulation when processor
 is suspended forever by WAIT instruction with interrupts disabled.
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To: Serge Vakulenko <serge@vak.ru>, qemu-devel@nongnu.org
Cc: Aurelien Jarno <aurelien@aurel32.net>

Hi Serge,

On 30/06/2015 06:02, Serge Vakulenko wrote:
> Signed-off-by: Serge Vakulenko <serge@vak.ru>
> ---
>  target-mips/op_helper.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/target-mips/op_helper.c b/target-mips/op_helper.c
> index 2a9ddff..1b7caeb 100644
> --- a/target-mips/op_helper.c
> +++ b/target-mips/op_helper.c
> @@ -22,6 +22,7 @@
>  #include "exec/helper-proto.h"
>  #include "exec/cpu_ldst.h"
>  #include "sysemu/kvm.h"
> +#include "sysemu/sysemu.h"
> 
>  #ifndef CONFIG_USER_ONLY
>  static inline void cpu_mips_tlb_flush (CPUMIPSState *env, int flush_global);
> @@ -2235,6 +2236,12 @@ void helper_wait(CPUMIPSState *env)
>  {
>      CPUState *cs = CPU(mips_env_get_cpu(env));
> 
> +#ifndef CONFIG_USER_ONLY
> +    if (!(env->CP0_Status & (1 << CP0St_IE))) {
> +        /* WAIT instruction with interrupts disabled - halt the simulation. */
> +        qemu_system_shutdown_request();
> +    }
> +#endif

Why do you want to stop the simulation, wouldn't it be beneficial to leave it
running? For debugging for example, the user would be still able to inspect
the state, that could help to find a clue why CPU got suspended forever.

Also, if we take into account implementations (currently not supported in
QEMU) where CPU can be woken up by a disabled interrupt (the Config7.WII bit
in P5600 for example), then this won't be correct.

Thanks,
Leon