Re: [PATCH v2] s390x/tcg: MVCL: Exit to main loop if requested

["Alex Bennée" <alex.bennee@linaro.org>]

David Hildenbrand <david@redhat.com> writes:

> On 04.10.19 14:11, Peter Maydell wrote:
>> On Fri, 4 Oct 2019 at 09:02, David Hildenbrand <david@redhat.com> wrote:
>>> So shall we leave this patch as-is (adding a summary of what you
>>> explained to the description) or shall we somehow factor out the
>>> TCG-internal-thingy check?
>>
>> Nothing else in target code touches the icount data structures,
>> so if this s390 insn needs to make this check I think it ought
>> to do it by calling a function implemented by the tcg code;
>> that can then have a good name that describes what it's doing
>> and a doc comment explaining the reason we need to have it.
>>
>> thanks
>> -- PMM
>>
>
> I can offer something like this:
>
> diff --git a/include/exec/exec-all.h b/include/exec/exec-all.h
> index 49db07ba0b..d370ac0134 100644
> --- a/include/exec/exec-all.h
> +++ b/include/exec/exec-all.h
> @@ -72,6 +72,26 @@ 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);
>
> +/**
> + * cpu_cond_loop_exit_restore:
> + * @cpu: the vCPU state to be restored
> + * @pc: the host PC
> + *
> + * Trigger a cpu_loop_exit_restore() in case somebody asked for a return
> + * to the main loop (e.g. cpu_exit() or cpu_interrupt()).
> + *
> + * This is helpful for architectures that support interruptible
> + * instructions. After writing back all state to registers/memory, this
> + * call can be used to conditionally return back to the main loop or to
> + * continue executing the interruptible instruction.
> + */
> +static inline void cpu_cond_loop_exit_restore(CPUState *cpu, uintptr_t pc)
> +{
> +    if (unlikely((int32_t)atomic_read(&cpu_neg(cs)->icount_decr.u32) < 0)) {
> +        cpu_loop_exit_restore(cs, ra);
> +    }
> +}
> +

cpu_loop_exit_restore_cond_irq
cpu_loop_exit_restore_ifirq
cpu_loop_exit_restore_conditional
cpu_loop_exit_restore_maybe

meh, naming stuff is hard:

Acked-by: Alex Bennée <alex.bennee@linaro.org>

>  #if !defined(CONFIG_USER_ONLY)
>  void cpu_reloading_memory_map(void);
>  /**
>
>
> Or, as alternative, something like "cpu_shall_exit()" which only
> wraps the single check.


--
Alex Bennée