Re: [PATCH v2 1/3] icount: preserve cflags when custom tb is about to execute

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

Richard Henderson <richard.henderson@linaro.org> writes:

> On 11/17/21 10:47 AM, Alex Bennée wrote:
>> -    gen_set_label(tcg_ctx->exitreq_label);
>> +    if (tcg_ctx->exitreq_label) {
>> +        gen_set_label(tcg_ctx->exitreq_label);
>> +    }
>>       tcg_gen_exit_tb(tb, TB_EXIT_REQUESTED);
>
> The exit_tb is also not reachable, and should go in with the label.

ok

>
>>   }
>>   modified   accel/tcg/cpu-exec.c
>> @@ -954,11 +954,16 @@ int cpu_exec(CPUState *cpu)
>>                * after-access watchpoints.  Since this request should never
>>                * have CF_INVALID set, -1 is a convenient invalid value that
>>                * does not require tcg headers for cpu_common_reset.
>> +             *
>> +             * As we don't want this special TB being interrupted by
>> +             * some sort of asynchronous event we apply CF_NOIRQ to
>> +             * disable the usual event checking.
>>                */
>>               cflags = cpu->cflags_next_tb;
>>               if (cflags == -1) {
>>                   cflags = curr_cflags(cpu);
>>               } else {
>> +                cflags |= CF_NOIRQ;
>>                   cpu->cflags_next_tb = -1;
>>               }
>
> Still missing something to avoid cpu_handle_interrupt firing?

Something as simple as:

--8<---------------cut here---------------start------------->8---
modified   accel/tcg/cpu-exec.c
@@ -721,6 +721,15 @@ static inline bool need_replay_interrupt(int interrupt_request)
 static inline bool cpu_handle_interrupt(CPUState *cpu,
                                         TranslationBlock **last_tb)
 {
+    /*
+     * If we have special cflags lets not get distracted with IRQs. We
+     * shall exit the loop as soon as the next TB completes what it
+     * needs to do.
+     */
+    if (cpu->cflags_next_tb != -1) {
+        return false;
+    }
+
     /* Clear the interrupt flag now since we're processing
      * cpu->interrupt_request and cpu->exit_request.
--8<---------------cut here---------------end--------------->8---

?

>
>
> r~


-- 
Alex Bennée