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References: <20140731125321.1600.46604.stgit@PASHA-ISP.novsu.ac.ru>
	<20140731125531.1600.81487.stgit@PASHA-ISP.novsu.ac.ru>
From: Alex =?utf-8?Q?Benn=C3=A9e?= <alex.bennee@linaro.org>
Date: Thu, 31 Jul 2014 17:17:29 +0100
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Subject: Re: [Qemu-devel] [RFC PATCH v3 22/49] cpu: invent instruction count
	for accurate replay
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To: Pavel Dovgalyuk <Pavel.Dovgaluk@ispras.ru>
Cc: peter.maydell@linaro.org, peter.crosthwaite@xilinx.com, mark.burton@greensocs.com, qemu-devel@nongnu.org, batuzovk@ispras.ru, maria.klimushenkova@ispras.ru, real@ispras.ru, pbonzini@redhat.com, afaerber@suse.de, fred.konrad@greensocs.com


Pavel Dovgalyuk writes:

> This patch adds instructions count fields to cpu structure and
> invents several functions for increasing this counter while executing
> translation blocks.
>
<snip>
> @@ -1186,6 +1188,7 @@ void qemu_init_vcpu(CPUState *cpu)
>      cpu->nr_cores = smp_cores;
>      cpu->nr_threads = smp_threads;
>      cpu->stopped = true;
> +    cpu->instructions_count = 0;
<snip>
> +    if (replay_file) {
> +        if (replay_mode == REPLAY_MODE_RECORD) {
> +            if (process_events && replay_has_events()) {
> +                replay_save_instructions();
> +                /* events will be after the last instruction */
> +                replay_save_events(-1);
> +            } else {
> +                /* instruction - increase the step counter */
> +                ++first_cpu->instructions_count;
> +            }
> +        } else if (replay_mode == REPLAY_MODE_PLAY) {
> +            skip_async_events_until(EVENT_INSTRUCTION);
> +            if (first_cpu->instructions_count >= 1) {
> +                ++replay_state.current_step;
> +                --first_cpu->instructions_count;
> +                if (first_cpu->instructions_count == 0) {
> +                    replay_has_unread_data = 0;
> +                }
> +            } else {
> +                replay_read_events(-1);
> +            }
> +        }
> +    }
> +}
> +
> +void replay_undo_last_instruction(void)
> +{
> +    if (replay_mode == REPLAY_MODE_RECORD) {
> +        first_cpu->instructions_count--;
> +    } else {
> +        replay_state.skipping_instruction = 1;
> +    }

I'm not quite following what instructions_count means here. Is it an
actual count of instructions executed? Can you add a comment to the
header where it's defined?

-- 
Alex Bennée