Re: [PATCH] accel/tcg: Expose translation block flags to plugins

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

Mikhail Tyutin <m.tyutin@yadro.com> writes:

> In system mode emulation, some of translation blocks could be
> interrupted on memory I/O operation. That leads to artificial
> construction of another translation block that contains memory
> operation only. If TCG plugin is not aware of that TB kind, it
> attempts to insert execution callbacks either on translation
> block or instruction, which is silently ignored.

That was the intention - the instrumented instructions have already been
executed. The only thing that matters now is the memory access:

    /*
     * Exit the loop and potentially generate a new TB executing the
     * just the I/O insns. We also limit instrumentation to memory
     * operations only (which execute after completion) so we don't
     * double instrument the instruction.
     */
    cpu->cflags_next_tb = curr_cflags(cpu) | CF_MEMI_ONLY | n;


> As the result
> it leads to potentially inconsistent processing of execution and
> memory callbacks by the plugin.
> Exposing appropriate translation block flag allows plugins to
> handle "memory only" blocks in appropriate way.

We don't want to expose internal details to the plugin. It shouldn't
need to care.

Do you have a test case where you missed counting the execution of the
instruction?

-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro